Download 2731-AQA Physics P3.3 SoW Keeping things moving

AQA Physics P3.3 Scheme of Work
Keeping Things Moving
Overview
The Big Picture for this unit
Without electricity where would humanity be? The fierce battle of the currents between Nikola
Tesla and Thomas Edison forged a technological path that we are still treading at an enormous
pace today.
Electric currents produce magnetic fields. Forces produced in magnetic fields can be used to
make things move. This is called the motor effect and is how appliances such as the electric motor
create movement. Our ability to exploit the motor effect of electricity has allowed us to develop into
the technological society of the 21st Century.
Many appliances do not use 230 volts mains electricity. Transformers are used to provide the
required potential difference. Without transformers we couldn’t distribute vast amounts of
electricity all over the world and we wouldn’t be able to charge laptops and mobile phones.
Without electricity where would humanity be?
Key Questions to ask students whilst teaching this unit
If electricity can kill you, how can it save lives?
Do bigger batteries make bulbs brighter?
Are battery-powered appliances safe in the bathroom?
Does electricity leak away?
Does the colour of the wire make a difference?
Is electricity pure energy?
Is it true that ‘volts jolt but current kills’?
Is lightning part of a circuit?
Is electricity natural or artificial?
Aren’t current and voltage both just ways of measuring electricity?
What are we paying for when we use electricity?
Where does electricity go when we switch off?
What is the point of earthing an appliance if earth doesn’t conduct?
Do we ever lose control of electricity?
Is static really electricity?
Do efficient electric kettles work quicker?
What makes a battery rechargeable?
If nerves are conductors, does the body have a battery?
Can you destroy electricity?
How can a battery be flat if current has flowed back into it?
Will electricity generation always cause problems?
Is total sustainability compatible with cheap electricity?
Common misconceptions held by students
Electricity is energy
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Keeping Things Moving – Outline lesson sequence
Lesson
Lesson 1
Main Focus of lesson
Electromagnets
Main LOs
Understand that a current in a
conductor produces a magnetic field
and that this is the basis for
electromagnets, applications of which
include their use on cranes for lifting
iron or steel.
Key activities
Ask the students to explain what happens
when two magnets are brought together.
Assessment
Exam Questions
Link to spec.
a) When a current flows
through a wire a magnetic
field is produced around the
wire.
Exam Questions
b) The motor effect and its
use.
c) The size of the force can
be increased by:
1. Increasing the
strength of the
magnetic field
2. Increasing the size
of the current.
d) The conductor will not
experience a force if it is
parallel to the magnetic
field.
e) The direction of the force
is reversed if either the
direction of the current or
the direction of the
magnetic field is reversed.
a) If an electrical
conductor ‘cuts’
through a magnetic
field a potential
difference is induced
across the ends of the
conductor.
b) If a magnet is moved
into a coil of wire a
potential difference is
induced across the
ends of the coil.
Demonstrate and explain electromagnet and
permanent magnet
Demonstrate and explain uses of
electromagnetism.
Lesson 2
The Motor Effect
Understand the principle of the
motor effect and know how to use
Fleming’s Left-hand Rule to identify
the direction of the force produced.
Know how the size and direction of
the force produced can be altered.
Exam question sheet.
Demonstrate and explain motor effect.
Students build model motors
Ask the students to make a list of everyday
devices that use electric motors.
Exam question sheet.
Lesson 3
Electromagnetic
Induction
Understand the principle of
electromagnetic induction.
Remind students of the National Grid
demonstration in Physics 1.
Exam Questions
Complete a labelled diagram of a transformer
and the National Grid.
Explore the difference between an iron core
transformer and an step down transformer.
Exam question sheet.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Lesson 4
Transformers
Understand the structure of the
transformer.
Students plan to make a model transformer
using C-cores and insulated wire.
Explain how a transformer works.
Exam question sheet.
Exam Questions
Understand the difference between
a step-up transformer and a stepdown transformer.
Use the transformer equation.
Lesson 5
Transformers in Action
Understand the difference between
a switch mode transformer and a
conventional transformer.
Know the advantages and uses of
switch mode transformers.
Remind students of the investigation they
planned last lesson.
Exam Questions
Carry out the investigation planned last
lesson to see how the output voltage of a
transformer depends on the number of turns.
Students report back on their findings.
VP NP

Introduce the transformer equation VS NS .
Complete the diagrams of step-up and stepdown transformers.
Exam question sheet.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
c) If an electrical
conductor ‘cuts’
through a magnetic
field a potential
difference is induced
across the ends of the
conductor.
d) If a magnet is moved
into a coil of wire a
potential difference is
induced across the
ends of the coil.
g) The potential difference
across the primary and
secondary coils of a
transformer are related by
the equation:
Vp / np = Vs / ns
h) If transformers are
assumed to be 100%
efficient,the electrical power
output would equal the
electrical power input.
Vp x Ip = Vs x Is
i) Switch mode
transformers operate at a
high frequency, often
between 50 kHz and 200
kHz.
j) Switch mode
transformers are much
lighter and smaller than
traditional transformers
working from a 50 Hz
mains supply. Candidates
should be aware that this
makes them useful for
applications such as mobile
phone chargers.
k) Switch mode
transformers use very little
power when they are
switched on but no load is
applied.
Lesson 1 – Electromagnets
Resources
Specification Reference P3.3.1
Bar magnets, iron filings
a) When a current flows through a wire a
magnetic field is produced around the wire.
Long nails, coil wires, paper clips, power
supply
Students should be able to:
Electric bell, circuit breaker
Understand that a current in a conductor
produces a magnetic field and that this is the
basis for electromagnets, applications of
which include their use on cranes for lifting
iron or steel.
Demonstration equipment for magnetic field
around a wire and solenoid;
Activities
S-cool revision topic ‘Magnetism and
Electromagnetism’ can be found in the GCSE
Physics section at www.s-cool.co.uk or by
searching for ‘electromagnetism’.
Assessment Opportunities
Ask the students to explain what happens
when two magnets are brought together.
Show the students how an
electromagnet can attract and repel a
permanent magnet. Also show how the
strength of the electromagnet depends on the
current in the coils.
Demonstrate uses of electromagnetism.
Explain circuit diagrams of practical
devices like an electric bell and a circuit
breaker.
Explain how a loudspeaker works. Draw
a diagram of its action.
Exam question sheet.
Use of data to draw a conclusion.
AFL open ended question.
Exam questions.
Learning Outcomes
All students must know:
Describe the effect that magnets have on
each other and on magnetic materials
Draw basic magnetic field patterns for a bar
magnet
Describe the key elements of an
electromagnet including the coil and iron core
Should:
Explain the function of basic electromagnetic
devices
Could:
Interpret diagrams of electromagnetic
appliances in order to explain how they work
Safety and Technicians’ Notes
Ensure students are not exposed to
dangerous amounts of electricity.
Check CLEAPPS for further information.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Lesson 2 – The Motor Effect
Resources
Specification Reference P3.3.1
Demonstration equipment for the motor effect
(rail track) and motor kits.
b) The motor effect and its use.
c) The size of the force can be increased by:
3. Increasing the strength of the magnetic
field
4. Increasing the size of the current.
d) The conductor will not experience a force if
it is parallel to the magnetic field.
e) The direction of the force is reversed if
either the direction of the current or the
direction of the magnetic field is reversed.
Useful information on an electric motor can
be found at www.schoolscience.co.uk by
searching for ‘electric motors’. An interactive
motor demonstration can be found at
www.walter-fendt.de/ph14e/electricmotor.htm
Assessment Opportunities
Use of data to draw a conclusion.
Students should be able to:
AFL open ended questions.
Understand the principle of the motor effect
and know how to use Fleming’s Left-hand
Rule to identify the direction of the force
produced.
Exam questions.
Know how the size and direction of the force
produced can be altered.
Activities
Learning Outcomes
All students must know:
The motor effect
The force is increased in a stronger magnetic
field
The force is increased with more current
Think through what happens when two
magnets interact. What will happen to a
magnet and an electromagnet.
Should know:
Demonstrate the motor effect with a rod
on a model rail track. Show how Fleming’s
left hand rule can be applied. Show that a rod
parallel to the magnetic field will not move.
Could know:
Fleming’s left hand (motor) rule
The construction of an electric motor
Safety and Technicians’ Notes
Let the students use model motors. Get
them to change the strength of the magnetic
field, by removing one magnet. Also run the
motor from one, two, three and then four
cells.
Ensure students are not exposed to
dangerous amounts of electricity.
Check CLEAPPS for further information.
Ask the students to make a list of
everyday devices that use electric motors.
Find out how maglev trains are being
developed for use across the world.
Exam question sheet.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Lesson 3 – Electromagnetic
Induction
Specification Reference P3.3.2
e) If an electrical conductor ‘cuts’ through a
magnetic field a potential difference is
induced across the ends of the conductor.
f) If a magnet is moved into a coil of wire a
potential difference is induced across the
ends of the coil.
Students should be able to:
Understand the principle of electromagnetic
induction.
Resources
Magnets, sensitive voltmeters, insulated wire,
computer access.
http://phet.colorado.edu
Nelson Thornes Physics page 258.
Nelson Thornes Physics CD-ROM Physics
P3 3.3 Transformers animation
Assessment Opportunities
Use of data to draw a conclusion.
AFL open ended question.
Activities
Exam questions.
Remind students of the National Grid
demonstration in Physics 1. The output of the
power station (25 kV) is increased to around
400 kV in the Grid. It is then reduced to 33 kV
and finally 230 V for houses. What devices do
this?
Learning Outcomes
Complete a labelled diagram of a
transformer and the National Grid.
All students must know:
How a transformer works
Transformers only work with a.c.
How step-up and step-down transformers are
used in the National Grid
Should know:
Explore the difference between an iron
core transformer and an step down
transformer. What are the pros and cons of
each type?
Exam question sheet.
High voltage is used in the National Grid to
reduce current and energy losses by heating
Could know:
Eddy currents in the core reduce the
efficiency of transformers
Safety and Technicians’ Notes
Ensure students are not exposed to
dangerous amounts of electricity.
Check CLEAPPS for further information.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Lesson 4 – Transformers
Resources
Specification Reference P3.3.2
An experiment that shows the basic principle
of any transformer can be found at
www.practicalphysics.org/go/Experiment_347
.html
g) The basic structure of a transformer
h) An alternating current in the primary coil
produces a changing magnetic field in the
iron core and hence in the secondary coil.
This induces an alternating potential
difference across the ends of the
secondary coil. Knowledge of laminations
and eddy currents in the core are not
required.
i) In a step-up transformer the potential
difference across the secondary coil is
greater than the potential difference
across the primary coil.
j) In a step-down transformer the potential
difference across the secondary coil is
less than the potential difference across
the primary coil.
Students should be able to:
Understand the structure of the transformer.
Explain how a transformer works.
Understand the difference between a stepup transformer and a step-down transformer.
Use the transformer equation.
Activities
Students plan to make a model
transformer using C-cores and insulated wire.
 Go over how a transformer works.
 Plan an investigation, based on the
apparatus already used, to find out
how the number of turns on the
primary and secondary coils affect the
transformer output
Nelson Thornes Physics page 258.
Nelson Thornes Physics CD-ROM Physics
P3 3.3 Transformers animation.
Assessment Opportunities
Use of data to draw a conclusion.
AFL open ended question.
Learning Outcomes
All students must know:
How a transformer works
Transformers only work with a.c.
How step-up and step-down transformers are
used in the National Grid
Should know:
High voltage is used in the National Grid to
reduce current and energy losses by heating
Could know:
Eddy currents in the core reduce the
efficiency of transformers
Safety and Technicians’ Notes
ICT Access?
Exam question sheet.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Lesson 5 – Transformers in
Action
Specification Reference P3.3.2
g) The potential difference across the primary
and secondary coils of a transformer are
related by the equation:
Vp / np = Vs / ns
h) If transformers are assumed to be 100%
efficient,the electrical power output would
equal the electrical power input.
Vp x Ip = Vs x Is
i) Switch mode transformers operate at a high
frequency, often between 50 kHz and 200
kHz.
j) Switch mode transformers are much lighter
and smaller than traditional transformers
working from a 50 Hz mains supply.
Candidates should be aware that this makes
them useful for applications such as mobile
phone chargers.
k) Switch mode transformers use very little
power when they are switched on but no load
is applied.
Resources
Iron C-cores, insulated wire, demonstration
transformer.
Computer simulations of transformer action
can be found at
www.micro.magnet.fsu.edu/electromag/java/tr
ansformer/index.html
Assessment Opportunities
Use of data to draw a conclusion.
AFL open ended question.
Exam questions.
Learning Outcomes
All students must know:
Step-up transformers increase voltage; stepdown decrease voltage
The transformer equation:
VP NP

VS NS
Students should be able to:
Should know:
Understand the difference between a switch
mode transformer and a conventional
transformer.
How step-up and step-down transformers are
used in the National Grid
Know the advantages and uses of switch
mode transformers.
Activities
Could know:
Eddy currents in the core reduce the
efficiency of transformers
Safety and Technicians’ Notes
Remind students of the investigation they
planned last lesson.
Carry out the investigation planned last
lesson to see how the output voltage of a
transformer depends on the number of turns.
Ensure students are not exposed to
dangerous levels of electricity.
Take care not to drop C-Cores on feet.
Check CLEAPPS for further information.
Students report back on their findings.
VP NP

VS NS
Introduce the transformer equation
.
Complete the diagrams of step-up and stepdown transformers.
Exam question sheet.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Student Checklist
P3.3 Keeping things moving
Before During Revision
1. Understand that a current in a conductor produces a
magnetic field and that this is the basis for electromagnets,
applications of which include their use on cranes for lifting
iron or steel.
2. Understand the principle of the motor effect and know how
to use Fleming’s Left-hand Rule to identify the direction of
the force produced.
3. Know how the size and direction of the force produced can
be altered.
4. Understand the principle of electromagnetic induction.
5. Understand the structure of the transformer.
6. Explain how a transformer works.
7. Understand the difference between a step-up transformer
and a step-down transformer.
8. Use the transformer equation.
9. Understand the difference between a switch mode
transformer and a conventional transformer.
10. Know the advantages and uses of switch mode
transformers.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Glossary
Alternating current
Electric current in a circuit that repeatedly reverses its direction.
Cable
Two or three insulated wires surrounded by an outer layer of rubber or
flexible plastic.
Circuit breaker
An electromagnetic switch that opens and cuts the current off if too much
current passes through it.
Conservation of
energy
Energy cannot be created or destroyed.
Coulomb (C)
The unit of electrical charge, equal to the charge passing a point in a
(direct current) circuit in 1 second when the current is 1 A.
Direct Current
Electric current in a circuit that is in one direction only.
Efficiency
Useful energy transferred by a device / total energy supplied to the
device.
Electric current
Flow of electric charge. The size of an electric current (in amperes, A) is
the rate of flow of charge.
Electrical energy
Energy transferred by the movement of electrical charge.
Electromagnetic
induction
The process of inducing a potential difference in a wire by moving the
wire so it cuts across the lines of force of a magnetic field.
Field line
See magnetic field line.
Force
A force can change the motion of an object (in newtons, N).
Frequency of an
alternating current
The number of complete cycles of oscillation per second, equal to 1/the
time period. The unit of frequency is the hertz (Hz).
Line of force
See magnetic field line.
Magnetic field line
Line in a magnetic field along which a magnetic compass points; also
called a magnetic field line or field line.
Magnetic poles
Ends of a bar magnet or a magnetic compass.
Motor effect
When a current is passed along a wire in a magnetic field and the wire is
not parallel to the lines of the magnetic field, a force is exerted on the
wire by the magnetic field.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
National Grid
The network of cables and transformers used to transfer electricity from
power stations to consumers (i.e. homes, shops, offices, factories, etc.).
North pole
North pointing end of a freely suspended bar magnet or of a magnetic
compass.
Potential difference
A measure of the work done or energy transferred to the lamp by each
coulomb of charge that passes through it. The unit of potential difference
is the volt (V).
Power
The energy transformed or transferred per second. The unit of power is
the watt (W).
South pole
South-pointing end of a freely suspended bar magnet or of a magnetic
compass.
Split-ring commutator
Metal contacts on the coil of a direct current motor that connects the
rotating coil continuously to its electrical power supply.
Step-down transformer
Electrical device that is used to step down the size of an alternating
voltage.
Step-up transformer
Electrical device that is used to step up the size of an alternating voltage.
Switch mode
transformer
A transformer that works at much higher frequencies than a traditional
transformer. It has a ferrite core instead of an iron core.
Transformer
Electrical device used to change an (alternating) voltage. See also Stepup transformer and Step-down transformer.
Volt (V)
The unit of potential difference, equal to energy transfer per unit charge
in joules per coulomb.
Wasted Energy
Energy that is not usefully transferred.
Watt (W)
The unit of power.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Glossary
Alternating current
Electric current in a circuit that repeatedly reverses its direction.
Cable
Two or three insulated wires surrounded by an outer layer of rubber or
flexible plastic.
Circuit breaker
An electromagnetic switch that opens and cuts the current off if too much
current passes through it.
Conservation of
energy
Energy cannot be created or destroyed.
Coulomb (C)
The unit of electrical charge, equal to the charge passing a point in a
(direct current) circuit in 1 second when the current is 1 A.
Direct Current
Electric current in a circuit that is in one direction only.
Efficiency
Useful energy transferred by a device / total energy supplied to the
device.
Electric current
Flow of electric charge. The size of an electric current (in amperes, A) is
the rate of flow of charge.
Electrical energy
Energy transferred by the movement of electrical charge.
Electromagnetic
induction
The process of inducing a potential difference in a wire by moving the
wire so it cuts across the lines of force of a magnetic field.
Field line
See magnetic field line.
Force
A force can change the motion of an object (in newtons, N).
Frequency of an
alternating current
The number of complete cycles of oscillation per second, equal to 1/the
time period. The unit of frequency is the hertz (Hz).
Line of force
See magnetic field line.
Magnetic field line
Line in a magnetic field along which a magnetic compass points; also
called a magnetic field line or field line.
Magnetic poles
Ends of a bar magnet or a magnetic compass.
Motor effect
When a current is passed along a wire in a magnetic field and the wire is
not parallel to the lines of the magnetic field, a force is exerted on the
wire by the magnetic field.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
National Grid
The network of cables and transformers used to transfer electricity from
power stations to consumers (i.e. homes, shops, offices, factories, etc.).
North pole
North pointing end of a freely suspended bar magnet or of a magnetic
compass.
Potential difference
A measure of the work done or energy transferred to the lamp by each
coulomb of charge that passes through it. The unit of potential difference
is the volt (V).
Power
The energy transformed or transferred per second. The unit of power is
the watt (W).
South pole
South-pointing end of a freely suspended bar magnet or of a magnetic
compass.
Split-ring commutator
Metal contacts on the coil of a direct current motor that connects the
rotating coil continuously to its electrical power supply.
Step-down transformer
Electrical device that is used to step down the size of an alternating
voltage.
Step-up transformer
Electrical device that is used to step up the size of an alternating voltage.
Switch mode
transformer
A transformer that works at much higher frequencies than a traditional
transformer. It has a ferrite core instead of an iron core.
Transformer
Electrical device used to change an (alternating) voltage. See also Stepup transformer and Step-down transformer.
Volt (V)
The unit of potential difference, equal to energy transfer per unit charge
in joules per coulomb.
Wasted Energy
Energy that is not usefully transferred.
Watt (W)
The unit of power.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Electromagnets Exam Questions
1.
The diagram below shows a door lock which can be opened from a flat inside a building.
(a)
Explain how the door is unlocked when the switch is closed.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(4)
(b)
State two changes which would increase the strength of the electromagnet.
1 ..................................................................................................................................
2 ..................................................................................................................................
(2)
(c)
Why is the spring needed in the lock?
....................................................................................................................................
....................................................................................................................................
(1)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(d)
The connections to the coil were accidentally reversed. Would the lock still work?
....................................................................................................................................
Explain your answer.
....................................................................................................................................
....................................................................................................................................
(2)
(Total 9 marks)
2.
Circuit breakers help to make the electricity supply in homes safer.
A circuit breaker is an automatic safety switch. It cuts off the current if it gets too big.
Re-set
button
Spring
+
–
Plastic
plunger
Electro- Iron bolt
magnet
Spring
Switch
is ON
Re-set
button
Plastic
plunger
+
–
Electro- Iron bolt
magnet
To house
circuit
appliances
Switch
is OFF
Describe, in as much detail as you can, how this circuit breaker works.
To gain full marks in this question you should write your ideas in good English. Put them into
a sensible order and use the correct scientific words.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
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...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
(Total 6 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
3.
The diagram shows a switch that is operated by an electromagnet.
Pivot
Iron arm
Electromagnet
Contacts
(i)
What is this type of switch called?
..........................................................................................................................
(1)
(ii)
The switch is used in a car starter motor circuit.
Ignition
key
M
Starter motor
Explain how turning the ignition key makes a current flow in the starter motor. The explanation
has been started for you.
When the ignition key is turned ......................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(3)
(Total 4 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Electromagnets Exam Questions Mark Scheme
1.
(a)
current flows4
coil / core magnetised / electromagnet activated / energised / turned on
attracts iron
bar
causing bolt to be pulled out
each for 1 mark
(b)
more turns
2
bigger current / e.m.f
softer iron core
any two for 1 mark each
(c)
to relock door / return iron bar / to lock door
for 1 mark
1
(d)
iron bar would still be attracted / coil still magnetised so still works
for 1 mark each
2
yes + wrong answer
0 marks
yes + current still flows
1 mark
yes + still magnetised / iron bar still attracted
2 marks
2.
Quality of written communication: One mark for correct sequencing.1
bolt out  plunger up  switch off / circuit
broken
any five from
high current flows
electromagnet is stronger
the iron bolt is pulled out
the plastic plunger moves up
the switch is lifted / open / off
accept circuit is broken
no current flowing
to re-set the plunger must be
pushed down
5
3.
1
(i)
relay
accept solenoid
do not accept magnetic switch
(ii)
a current flows through the coil (of the electromagnet)1
or a current flows through the electromagnet
or a
(magnetic) field is produced
accept ‘electricity’ for ‘current’
accept the electromagnet is activated or magnetised or turned on
do not accept answer in terms of magnetic charge
the (iron) arm is attracted to the electromagnet
accept the arm pivots or moves towards the electromagnet
1
the contacts are pushed together
do not accept contacts attract
1
[4]
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
The Motor Effect Exam Questions
1.
The diagram shows a simple electric motor.
The coil rotates as shown in the diagram.
(a)
State two ways of reversing the direction of forces F1 and F2.
1.
...........................................................................................................................
.....................................................................................................................................
2.
...........................................................................................................................
.....................................................................................................................................
(2)
(b)
Give two ways in which the size of the forces can be increased.
1.
...........................................................................................................................
.....................................................................................................................................
2.
...........................................................................................................................
.....................................................................................................................................
(2)
(Total 4 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
2.
(a)
The diagram shows one way of demonstrating a particular electrical effect.
N
S
As the wire is moved downwards between the poles of the magnet the ammeter needle swings to
the right.
(i)
What name is given to this electrical effect?
...........................................................................................................................
(1)
(ii)
What happens to the ammeter needle when the wire is moved upwards between the poles of
the magnet?
...........................................................................................................................
(1)
(iii)
When the wire is held stationary between the poles of the magnet the ammeter needle does
not move. Explain why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(b)
Complete the following sketch graph to show one complete cycle of an alternating current.
Current
Time
(1)
(Total 5 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
3.
The diagram shows apparatus used to demonstrate the electric motor effect. When he switch is closed the
wire moves.
Metal rail
Movable wire
Metal rail
(i)
Draw an arrow on the diagram to show the direction the wire moves.
(1)
(ii)
Explain why the wire moves.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 3 marks)
4.
The diagram shows apparatus used to demonstrate the motor effect. X is a short length of bare copper
wire resting on two other wires.
Horseshoe
magnet
Bare copper
wire
+
Red
Switch
–
Black
Power supply
Bare copper wire (X)
(a)
(i)
Describe what happens to wire X when the current is switched on.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(ii)
What difference do you notice if the following changes are made?
A
The magnetic field is reversed.
...........................................................................................................................
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
...........................................................................................................................
B
The current is increased.
...........................................................................................................................
...........................................................................................................................
(3)
(b)
The diagram shows a coil placed between the poles of a magnet. The arrows on the sides of the
coil itself show the direction of the conventional current.
Pivot
Coil
Magnet
F
N
S
F
The arrows labelled F show the direction of the forces acting on the sides of the coil. Describe the
motion of the coil until it comes to rest.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(c)
Most electric motors use electromagnets instead of permanent magnets. State three of the features
of an electromagnet which control the strength of the magnetic field obtained.
1 ................................................................................................................................
2 ................................................................................................................................
3 ................................................................................................................................
(3)
(Total 9 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
5.
The diagram below shows a rectangular coil of wire between the poles of a magnet.
The two ends of the coil make contact with two slip rings.
The slip rings are connected at points X and Y to a centre-zero meter.
(a)
(i)
Describe what happens to the meter needle if the coil is rotated in the magnetic field.
...........................................................................................................................
...........................................................................................................................
(2)
(ii)
Explain your answer.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(b)
The meter is now removed from the circuit.
The contacts at X and Y are then connected to the inputs of a cathode ray oscilloscope.
The grid below shows the trace on the oscilloscope when the coil is rotated at a steady rate in the
magnetic field.
The speed of rotation of the coil is now doubled.
On the grid below sketch the trace which you would expect to see on the oscilloscope screen.
The controls of the oscilloscope have not been changed.
(3)
(Total 7 marks)
6.
(a)
The diagram shows a loop of wire which is being moved rapidly down between the poles of a
magnet.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
0
mA
What will be the reading on the milliammeter as the loop of wire moves down?
....................................................................................................................................
Give a reason for your answer.
....................................................................................................................................
....................................................................................................................................
(2)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(b)
The diagram shows one way of measuring the rate of flow of fluid through a pipe.
Explain how the flow of fluid through the pipe causes an alternating current to be induced in the
solenoid.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(3)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(c)
The graph shows how the milliammeter reading changes with time when a fluid flows at a steady
rate through the pipe.
20
15
Current in 10
milliamps
5
0
–5
–10
–15
–20
0
10 20 30 40 50 60 70 80
Time in milliseconds
Draw on the grid below, a graph to show how the milliammeter reading would change if the fluid
flow is increased, so that the turbine rotates twice as fast.
20
15
Current in 10
milliamps
5
0
–5
–10
–15
–20
0
10 20 30 40 50 60 70 80
Time in milliseconds
(2)
(Total 7 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Motor Effect Exam Questions Mark Scheme
1.
2.
(a)
reverse the current 1
reverse the magnetic field
accept swap the magnets over
1
(b)
increase the strength of the magnetic field
accept use stronger magnets do not accept use bigger magnets
1
increase the size of the current
1
(i)
(electromagnetic) induction
accept inducing current
1
(ii)
swings to the left
accept moves to left or moves the other way
accept it will go to – 1
do not accept moves back to zero
1
(iii)
no (induced) current when
accept no (induced) voltage
1
no (relative) movement between conductor and magnetic field
do not accept wire not moving
accept ‘field’ or ‘magnet’ for ‘magnetic field’
accept no change of flux linkage
accept conductor or wire not cutting the field
accept no change in magnetic field around wire
do not accept field not broken
1
(a)
(b)
one complete cycle shown
curve should be regular
do not accept more than one cycle
accept good sawtooth or square wave
3.
1
(i)
away from magnet
1
arrow should be perpendicular to field lines and current as judged by eye
(ii)
current in wire creates magnetic field around wire
1
two fields interact or combine giving a resultant force (on the wire)
1
[3]
4.
(a)
(b)
(i)
it moves or experiences a force horizontally to the right
for 1 mark
(ii)
A - moves in opposite direction or force reversed e.c.f. 2
B - faster movement or larger force
(not
move further)
for 1 mark each
turns clockwise3
oscillates/reverses
comes to rest facing field/at 90o to field/vertically
for 1 mark each
(c) number of turns or linear number density of turns
for 1 mark each
5.
(a)
1
(i)
3
current
core
the ammeter needle will deflect/will register a reading/will 2
move from zero position
the deflection of the ammeter reading will be repeatedly to and fro/
will keep changing direction
for 1 mark each
(ii)
the moving coil of wire cuts through/across the magnetic 2
field/flux/lines of force
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
the direction of movement of the opposite sides of the coil reverses every half cycle/revolution
for 1 mark each
twice the frequency/half the wavelength
3
(i.e. two and half cycles shown)
for 2 marks
(b)
else greater frequency/more cycles/shorter “wavelength”
for 1 mark
greater amplitude/height
for 1 mark
6.
(a)
zero
1
not it stays the same
(induced) currents or (induced)
1
voltages on either side of loop oppose
accept generated currents generated voltages
not wire moves out of field
(b)
magnets turn or rotate or spin or
giving (relative) movement between
accept coil
1
move
1
magnetic (field) and solenoid
field linkage increases then decreases
1
i.e. a.c.
accept answer in terms of pushing a magnet into and pulling a magnet out of a
solenoid
accept field changes
i.e.
1st mark  magnets moving
2nd mark  field/magnet interacts with coil
3rd mark  the interaction is changing
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Electromagnetic Induction Exam Questions
1.
The equipment shown was used to produce the trace on the computer screen.
Describe and explain what was done with the equipment to produce this trace.
To gain full marks for this question, you should write your ideas in good English. Put them in a sensible
order and use the correct scientific words.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
(Total 4 marks)
2.
(a)
The diagram shows a magnet being moved into a coil of wire.
The reading on the meter is shown in the diagram.
0
–
N
+
S
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Draw on the diagram the meter reading that you would expect to get in each of the following cases.
(i)
The magnet is at rest inside the coil.
0
–
N
+
S
(1)
(ii)
The magnet is moved out of coil.
0
–
N
+
S
(1)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
To gain full marks in this question you should write your ideas in good English. Put them into a
sensible order and use the correct scientific words.
(b)
The diagram below shows a bicycle dynamo and part of the wheel.
Tyre
N
S
Magnet
Coil on soft-iron core
Wires to lamp
Explain, as fully as you can, why a current flows through the bicycle lamp when the wheel of the
bicycle turns.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(4)
(Total 6 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Electromagnetic Induction Exam Questions Mark Scheme
1.
Quality of written communication:
1
1 mark for correct sequencing
magnet in produces voltage / current
→ magnet out produces voltage /
current → in opposite direction
any three from:
3
magnet moved to coil / coil
moved to magnet
produces a current / voltage
correct reference to induction
magnet moved from coil / coil moved from magnet
produces current / voltage
correct reference to reversal of current / voltage
2.
(a)
(i)
pointer at 0
1
(ii)
pointer to left of 0
1
Quality of Written Communication
The answer to this part of the question requires ideas in good English, in a sensible order with correct use of
scientific terms. Quality of written
communication should be considered in crediting points in the mark
scheme.
Max. 3 if ideas not well expressed.
(b)
magnet turns
1
changing magnetic field in coil or core
1
so induces a voltage
causing a current to flow
1
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
1
T. Baylis
Transformers Exam Questions
1.
The outline diagram below shows part of the National Grid. At X the transformer increases the voltage to
a very high value. At Y the voltage is reduced to 240 V for use by consumers.
Power station
(i)
Transformer
X
Transformer
Y
The frequency of the mains supply to houses is 50 Hz. Explain what this means.
.....................................................................................................................................
.....................................................................................................................................
(2)
(ii)
At X a transformer increases the voltage. What happens to the current as the voltage is increased?
.....................................................................................................................................
(1)
(iii)
Why is electrical energy transmitted at very high voltages?
.....................................................................................................................................
.....................................................................................................................................
(1)
(iv)
The transformer at Y reduces the voltage before it is supplied to houses. Why is this done?
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 5 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
2.
The drawing shows an experiment using a low voltage supply, a joulemeter, a small immersion heater
and a container filled with water.
The immersion heater is designed for use in a tropical fish tank. It is connected to a step-down
transformer supplied by 230 V a.c. mains.
The inside of a step-down transformer consists of three main parts. Name the three parts and briefly describe
them. You may add to the diagram to help you to answer.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
(Total 4 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
3.
(a)
The drawing shows a small transformer used to recharge the battery in a 4.2 V mobile phone from
a 230 V mains supply.
Explain how you know that this is a step-down transformer.
.....................................................................................................................................
.....................................................................................................................................
(1)
(b)
A transformer consists of an insulated coil of wire, called the primary coil, on one side of a core.
Another coil of insulated wire, called the secondary coil, is on the other side.
Give two features of the core.
1 ..................................................................................................................................
2 ..................................................................................................................................
(2)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(c)
Electricity is transmitted for long distances at voltages of 400 kV.
Explain one advantage and one disadvantage of using such high voltages.
Advantage .................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
Disadvantage .............................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(d)
What charge, measured in coulombs (C), is passed when a voltage of 400 kilovolts (kV) transfers
200 megajoules (MJ) of energy?
voltage =
energy
charge
.....................................................................................................................................
.....................................................................................................................................
Charge = .................................................... C
(3)
(Total 10 marks)
4.
(a)
Electrical energy is distributed around the country by a network of high voltage transmission
cables.
Transmission
Cables
Consumer
A
Power
station
Transformer
Transformer
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(i)
For the system to work the power is generated and distributed using alternating current
rather than direct current. Why?
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Transformers are an essential part of the distribution system. Explain why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(b)
The power station generates 100 MW of power at a voltage of 25 kV. Transformer A, which links
the power station to the transmission cables, has 44 000 turns in its 275 kV secondary coil.
(i)
Write down the equation which links the number of turns in each transformer coil to the
voltage across each transformer coil.
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Calculate the number of turns in the primary coil of transformer A. Show clearly how you
work out your answer.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
Number of turns = .......................
(2)
(Total 6 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Transformers Exam Questions Mark Scheme
1.
(i)
current reverses;
for 1 mark each
(ii)
reduces
2
50 × each second (100?)
1
for 1 mark
(iii)
less heat/energy/power wasted
for 1 mark
(iv)
for safety
1
(in power lines)
1
for 1 mark
2.
each mark may be gained from a written description or from a caption on the
diagram or from both together but do not credit if there is any contradiction between
them
one coil on each side
1
of insulated wire
1
or insulated coil
number of turns on primary coil/1
coil 1/input coil greater than number of
turns on the secondary coil/
coil
2/output coil
this must be clear for example do not credit more coils do not credit bigger coil
core of laminated iron
or core of (soft) iron
1
3.
(a)
output voltage less than (the) input voltage
or p.d. across output less that p.d.
across input or output is (only) 4.2 V
(whereas) the input is 230V
or WTTE (words to that effect)
1
(b)
any two from
2
(made of soft) iron
laminated
or designed to reduce eddy currents
or made of thin slices with slices of insulating material between them
core(s) joined to make a ring
(c)
ADVANTAGE
2
any two from
current will be (relatively) low(er)
power / heat / energy losses will be low(er)
(so) more efficient
do not credit cheaper
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
DISADVANTAGE
EITHER
difficult to insulate
1
(so) difficult to prevent discharge to earth
or (hence) pylons have to be tall (accept big)
or (hence) pylons are expensive
or (so) danger of (lethal electric)
shock(s)
do not credit dangerous or expensive
1
OR
difficult to switch
1
(so) arcing problems
1
OR
transformers (required)
1
step-up (transformers at the supply end) and step-down 1
(transformers at the demand end)
candidate does not have to specify but
do not credit if candidate specifies
incorrectly
or transformers are expensive
(d)
EITHER
500 (C)
3
accept 0.5 (c) (1) mark 3
OR
charge = energy ÷ voltage
1
(charge =)
200 000 000 ÷ 400 000
1
[10]
4.
(a)
(i)
transformers only work with ac.
(ii)
used to increase or decrease or
1
1
change voltage or current
reducing the energy or heat or1
power loss (along the cables)
or reduce to safe domestic level
must be consistent with first answer
(b)
(i)
voltage across primary = no of turns in primary
voltage across secondary no of turns in secondary
1
accept =
or
=
(ii)
NP = 4000
=
for 1 mark
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
2
T. Baylis
Transformers in Action Exam Questions
1.
The diagram below shows a transformer.
V
240 V
a.c.
input
primary
coil
(i)
secondary
coil
Name the material used to make the core of the transformer.
.....................................................................................................................................
(1)
(ii)
The primary coil has 48 000 turns and the secondary coil 4000 turns.
If the input voltage is 240 V a.c., calculate the output voltage.
.....................................................................................................................................
.....................................................................................................................................
Answer ......................................... V
(2)
(iii)
Explain how the use of such a transformer could be adapted to transform a low voltage into a
higher voltage.
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 4 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
2.
(a)
An appliance in a house has a transformer. The transformer is used to reduce the voltage to the
level needed by the appliance.
The diagram shows the transformer.
10 000 turns
2000 turns
240 V a.c.
(i)
Name the material used for the core of the transformer.
...........................................................................................................................
(1)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(ii)
The transformer has 10 000 turns on the input side and 2000 turns on the output side. If the
mains voltage of 240 volts is applied to the input, calculate the output voltage. You may
find the following information helpful:
output voltage
number of turns on output coil
=
input voltage
number of turns on input coil
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(b)
Explain, in terms of magnetic fields, how a transformer works.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(c)
A 12 V car battery is connected to the input leads of the transformer. It is hoped to reduce the
voltage to 2.4 V in order to run a small motor. When the output voltage is measured it is found to
be zero.
Explain why the output voltage is zero.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 10 marks)
3.
 Diagram 1 shows a magnet being moved into a coil.
 Diagram 2 shows a magnet stationary in a coil.
 Diagram 3 shows a magnet being moved out of a coil.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
The meter looks like this when no current is flowing.
(a)
The position of the meter pointer has been drawn on diagram 1.
Draw the positions of the meter pointer on diagrams 2 and 3.
S
Magnet moving
into coil
N
Diagram 1
Centre 0
meter
Coil of wire
Diagram 2
S
Magnet stationary
in coil
N
Coil of wire
Centre 0
meter
Magnet moving
out of coil
N
Diagram 3
Centre 0
meter
Coil of wire
(2)
(b)
Bicycle dynamos generate electricity by rotating a magnet inside a coil of wire.
Give two ways of increasing the voltage produced by this kind of generator.
1 ..................................................................................................................................
2 ..................................................................................................................................
(2)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(Total 4 marks)
4.
(a)
The diagram represents a simple transformer used to light a 12 V lamp. When the power supply is
switched on the lamp is very dim.
Laminated iron core
a. c.
input
(i)
Primary
coil
Secondary
coil
12 V
Give one way to increase the voltage at the lamp without changing the power supply.
............................................................................................................................
............................................................................................................................
(1)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
5.
(a)
The diagram shows a simple step-up transformer. It is designed to light a 6 V lamp using a 1.5 V
power supply.
Core
1.5 V primary
(input)
(i)
Primary
(input)
coil
Secondary
(output)
coil
6V
Which one of the following power supplies should be used?
Draw a ring around your answer.
(1)
(ii)
Which one of the following metals is used to make the core of the transformer?
Draw a ring around your answer.
aluminium
copper
iron
steel
(1)
(iii)
Complete this sentence by crossing out the two lines in the box that are wrong.
If there are 20 turns of wire on the primary (input) coil, there will be
less than 20
exactly 20
more than 20
turns of wire on the secondary (output) coil.
(1)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(b)
The graph shows how the potential difference across the secondary (output) coil of a transformer
changes as the potential difference across the primary (input) coil is changed.
12.0
10.0
Potential
8.0
difference
across the
secondary 6.0
(output) coil
in volts
4.0
2.0
0.0
0.0
1.0
2.0
3.0
Potential difference across the
primary (input) coil in volts
4.0
How does the graph show that the transformer is a step-up transformer?
...............................................................................................................................................
...............................................................................................................................................
(1)
(c)
The diagram shows how the National Grid transmits electrical energy over long distances.
Complete the sentences by choosing the correct word or phrase from the box.
Each word or phrase may be used once or not at all.
current
less
more
potential difference
resistance
The step-up transformer increases the ...........................................................at which the
electrical energy is transmitted through the cables. The transformer also reduces the
....................................... in the cables. This makes the whole system......................
efficient.
(3)
(Total 7 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(ii)
What is meant by the iron core being laminated?
............................................................................................................................
............................................................................................................................
(1)
(b)
Electrical energy is distributed around the country by a network of high voltage cables.
Transmission
Cables
Consumer
A
Power
station
(i)
Transformer
Transformer
For the system to work the power is generated and distributed using alternating current
rather than direct current. Why?
............................................................................................................................
............................................................................................................................
(1)
(ii)
Transformers are an essential part of the distribution system. Explain why.
............................................................................................................................
............................................................................................................................
............................................................................................................................
(2)
(iii)
The transmission cables are suspended high above the ground. Why?
............................................................................................................................
(1)
(c)
The power station generates 100 MW of power at a voltage of 25 kV. Transformer A, which links
the power station to the transmission cables, has 44 000 turns in its 275 kV secondary coil.
(i)
Write down the equation which links the number of turns in each transformer coil to the
voltage across each transformer coil.
............................................................................................................................
............................................................................................................................
(1)
(ii)
Calculate the number of turns in the primary coil of transformer A. Show clearly how you
work out your answer.
............................................................................................................................
............................................................................................................................
............................................................................................................................
Number of turns = ........................................
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(2)
(d)
The diagram shows how the cost of transmitting the electricity along the cables depends upon the
thickness of the cable.
Cost
Cost of buying and
installing the cable
Cost due to heating
losses in the cable
Thickness of cable
(i)
Why does the cost due to the heating losses go down as the cable is made thicker?
............................................................................................................................
(1)
(ii)
By what process is most heat energy lost from the cables?
............................................................................................................................
(1)
(Total 11 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
6.
(a)
The diagram shows a simple step-up transformer. It is designed to light a 6 V lamp using a 1.5 V
power supply.
(i)
How can you tell from the diagram that this is a step-up transformer?
...........................................................................................................................
(1)
(ii)
Which material is used to make the core of a transformer?
...........................................................................................................................
(1)
(iii)
State two ways in which the design of the transformer could be changed to reduce the
brightness of the lamp.
1 ........................................................................................................................
...........................................................................................................................
2 ........................................................................................................................
...........................................................................................................................
(2)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(b)
Chris investigates three different transformers. For each transformer Chris changes the potential
difference across the primary (input) coil and measures the potential difference across the
secondary (output) coil.
The results for each transformer are given in the graph.
6.0
J
K
5.0
Potential
difference 4.0
across the
secondary 3.0
(output) coil
in volts 2.0
L
1.0
0.0
0.0
0.5 1.0 1.5 2.0 2.5 3.0
Potential difference across the
primary (input) coil in volts
Which of the transformers, J, K or L, is working as a step-down transformer?
.....................................................................................................................................
Give a reason for your answer.
.....................................................................................................................................
.....................................................................................................................................
(2)
(c)
The diagram shows how the National Grid transmits electrical energy over long distances.
(i)
Why do the power stations generate a.c. and not d.c?
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(1)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(ii)
State the purpose of transformer A and explain why it is an essential part of the National
Grid system.
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(3)
(Total 10 marks)
7.
The diagram shows Sue’s design for a simple wind speed gauge.
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
(a)
Explain why the wind causes the a.c. voltmeter to give a reading. The explanation has been started
for you.
The wind causes the plastic cups to turn. This causes the spindle and ......................
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(3)
(b)
Why does the voltmeter reading increase as the wind speed increases?
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(1)
(c)
The gauge is not sensitive enough to measure light winds.
Give one way that Sue can modify the design to make the gauge more sensitive.
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(1)
(d)
How could Sue make the gauge monitor and record wind speed automatically?
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(1)
(Total 6 marks)
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis
Transformers in Action Exam Questions Mark Scheme
1.
(i)
iron
1
for 1 mark
(ii)
20
2
gains 2 marks
else working
gains 1 mark
(iii)
reverse input/output
for 1 mark
1
or increase secondary turns
2.
(a)
(i)
Iron
1
for 1 mark
(ii)
(b)
5.
(b)
V/240 = 2000/10 000
for 1 mark each
3
V = 48
V
changing current in primary4
causes changing (magnetic) field in core
links to secondary
inducing voltage
(emf) in secondary (NOT current)
secondary voltage/current is alternating
for 1 mark each
(a)needle at 0
1
needle to left of 0
1
any two from
2
increase speed / pedal faster
increase strength of magnet
increase number of turns on coil /
number of coils
increase area of coil
(c) magnetic field not changing/no electromagnetic induction 2
because direct current
for 1 mark each
3.
(a)
(b)
(i)
one of the following:
•
increase number of turns on the secondary coil
•
decrease number of turns on the primary coil
1
(ii)
constructed in (thin) layers
1
(i)
transformers only work with a c
1
(ii)
used to increase or decrease or change voltage or current
1
reducing the energy or heat or power loss (along the cables)
or reduce to safe domestic level
1
must be consistent with first answer
(iii)
(several metres of) air gives good electrical
1
insulation (between cables and earth) or reduce chance
of earthing or sparks or arcing or to avoid people touching it
4.
(a)
(b)
(i)
B
1
(ii)
iron
1
(iii)
more than 20
1
pd across secondary is (always) bigger than pd across primary coil
accept voltage for pd
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
1
T. Baylis
(c)
5.
potential difference
(a)
(b)
(c)
1
current
1
more
1
(i)
more turns / coils on the secondary than primary
1
accept output for secondary
accept input for primary
accept converse
(ii)
iron
(iii)
decrease number turns on secondary
1
increase number turns on primary
do not accept reduce voltage of power supply
1
L
1
pd across secondary is smaller than pd across primary
accept voltage for pd
1
(i)
transformers only work with a.c.
accept converse
accept transmission system would be very inefficient if d.c. used
1
(ii)
to increase the pd at which the energy is transmitted
1
any two from:
2
1
energy / power losses (from cables) are much lower
reduces current in cables
cables heat up less
efficiency of system increases
6.
(a)
magnet to turn
1
magnetic field cut by the coil
1
or
rotating magnetic field links with the coil
accept magnetic field links with coil
accept voltage for pd
(b)
(c)
(d)
potential difference induced across coil
1
any one from:
1
•
speed of rotation of magnet increases
•
magnetic field lines cut at a faster rate
•
rate of change of flux linkage increases
any one from:
•
increase number of turns on coil
•
use stronger magnet
•
use larger cups
•
use more cups
•
use a millivoltmeter
any one from:
•
•
1
1
replace the voltmeter with a datalogger
•
connect voltmeter to a computer
record output with a computer
AQA GCSE Physics P3.3 Scheme of Work: Keeping Things Moving
T. Baylis