Download P3 10 Motor Effect

P3 10 Motor Effect Exam Questions
154 minutes
154 marks
Q1.
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.
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)
Q2.
A fault in an electrical circuit can cause too great a current to flow.Some circuits are
switched off by a circuit breaker.
One type of circuit breaker is shown above. A normal current is flowing.
Explain, in full detail, what happens when a current which is bigger than normal flows.
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(Total 4 marks)
Q3.
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.
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(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?
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(1)
(d)
The connections to the coil were accidentally reversed. Would the lock still work?
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Explain your answer.
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(2)
(Total 9 marks)
Q4.
The diagram shows apparatus used to demonstrate the motor effect. X is a short length of
bare copper wire resting on two other wires.
(a)
(i)
Describe what happens to wire X when the current is switched on.
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(ii)
What difference do you notice if the following changes are made?
A
The magnetic field is reversed.
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B
The current is increased.
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(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.
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.
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(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)
Q5.
The diagram shows a switch that is operated by an electromagnet.
(i)
What is this type of switch called?
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(1)
(ii)
The switch is used in a car starter motor circuit.
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 ..................................................................................
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(3)
(Total 4 marks)
Q6.
The diagram shows apparatus used to demonstrate the electric motor effect. When he
switch is closed the wire moves.
(i)
Draw an arrow on the diagram to show the direction the wire moves.
(1)
(ii)
Explain why the wire moves.
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(2)
(Total 3 marks)
Q7.
(a)
Name a material that could be used to make the outside case of the plug.
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Give a reason for your choice.
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(2)
(b)
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.
Some electrical circuits are protected by a circuit breaker. These switch the circuit off if a
fault causes a larger than normal current to flow. The diagram shows one type of circuit
breaker. A normal current (15 A) is flowing.
Source: adapted from V. PRUDEN and K. HIRST, AQA GCSE SceinceReproduced by permission of
Hodder and Soughton Educational Ltd
Explain what happens when a current larger than 15A flows. The answer has been
started for you.
When the current goes above 15 A, the electromagnet becomes stronger and
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(3)
(Total 5 marks)
Q8.
The diagram shows the design for a remotely controlled door bolt.
When the correct numbers are entered into the keypad the transformer switches on. Then the
door can be opened.
(a)
What kind of transformer is shown in the diagram?
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(1)
(b)
What does the abbreviation a.c. stand for?
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(1)
(c)
Complete the sentences using the correct words from the box.
attracts
downwards
sideways
switch
magnet
transformer
reflects
repels
upwards
(i)
When a current flows in the coil, the coil becomes a ................................... .
(ii)
The coil ................................... the iron bolt which moves ............................
(3)
(Total 5 marks)
Q9.
When a conductor carrying an electric current is placed in a magnetic field a force may act
on it.
(a)
State two ways in which this force can be increased.
1 ..................................................................................................................................
2 ..................................................................................................................................
(2)
(b)
State two ways in which this force can be made to act in the opposite direction.
1 ..................................................................................................................................
2 ..................................................................................................................................
(2)
(c)
In what circumstance will no force act on a conductor carrying an electric current and in a
magnetic field?
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(1)
(Total 5 marks)
Show clearly how you work out your answer.
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Kinetic energy = ............................................... J
(2)
(Total 7 marks)
Q10.
Many electrical appliances use the circular motion produced by their electric motor.
(a)
Put ticks (
motor.
) in the boxes next to all the appliances in the list which have an electric
electric drill
electric fan
electric food mixer
electric iron
electric kettle
electric screwdriver
(2)
(b)
One simple design of an electric motor is shown in the diagram. It has a coil which spins
between the ends of a magnet.
(i)
Give two ways of reversing the direction of the forces on the coil in the electric
motor.
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2 ........................................................................................................................
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(2)
(ii)
Give two ways of increasing the forces on the coil in the electric motor.
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2 ........................................................................................................................
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(2)
(Total 6 marks)
Q11.A student used the apparatus shown in the diagram to investigate how the weight supported by
an electromagnet depends on:
•
the current, I, flowing through the wire
•
the number of turns of wire, n, wrapped around the iron core.
For different values of I and n the student measured the maximum weight supported by the
electromagnet.
(a)
Which one of the following is the circuit symbol for a variable resistor?
Draw a ring around one answer.
(1)
(b)
The student obtained the three sets of results given below.
I = 2.5 A
n = 20
I = 1.0 A
n = 30
I = 2.0 A
n = 10
W = 6.4 N
W = 6.5 N
W = 3.7 N
Considering only these results, explain why it is not possible to come to any conclusion
about how I and n separately affect the strength of the electromagnet.
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(2)
(c)
The student obtained more results, and plotted the graph shown below.
Analyse all the results on the graph to draw conclusions for this investigation.
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(5)
(d)
The greater the weight supported, the stronger the electromagnet.
The smallest current that gives an electromagnet maximum strength is called
thesaturation current.
What is the saturation current for the electromagnet with 30 turns of wire?
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(1)
(e)
The diagram shows the circuit for the electric starter motor of a car. The circuit includes a
relay switch, which is a switch closed by an electromagnet.
(i)
Explain how turning the ignition key causes the starter motor to work.
The explanation has been started for you.
When the ignition key is turned the switch S closes and ...
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(4)
(ii)
Electric starter motors are always less than 100% efficient.
Explain why.
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(3)
(Total 16 marks)
Q12.
In this question you will be assessed on using good English, organising information
clearlyand using specialist terms where appropriate.
The diagrams show a relay switch and how it is used in a car ignition circuit.
Turning the ignition key closes the ignition switch.Explain how this causes the starter motor to
operate.
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(Total 6 marks)
Q13.
The diagram shows the equipment used by a student to investigate the strength of five
different electromagnets.
The stronger the electromagnet, the more paper clips it will hold.
(a)
Why is it important that the paper clips used in the investigation are all the same size?
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(1)
(b)
The five electromagnets, J, K, L, M and N, used by the student are shown below.
Each electromagnet was made by wrapping lengths of insulated wire around identical iron
nails.
The student wants to find out how the strength of an electromagnet depends on the
number of turns of wire in the coil.
Which electromagnets should the student compare in order to do this?
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(1)
(c)
The student concluded:
“The strength of an electromagnet is always directly proportional to the number of turns on
the coil.”
(i)
Explain how the data from the investigation supports the student’s conclusion.
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(2)
(ii)
The student makes one more electromagnet by winding 100 turns onto a nail.
Before testing the electromagnet, the student predicted the number of paper clips
that the electromagnet would hold when the current is 1 amp.
How many paper clips should the student predict that the electromagnet would
hold?
Show clearly how you work out your answer.
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number of paper clips = .....................................
(2)
(iii)
When the student tested the electromagnet it held 20 paper clips.This is not what
the student predicted.
Explain what the student should do when new data does not seem to support the
prediction that was made.
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(3)
(Total 9 marks)
Q14.
(a)
A laboratory technician sets up a demonstration.
A flexible wire is suspended between the ends of a horseshoe magnet. The flexible wire
hangs from a cotton thread. When the switch is closed, the wire kicks forward.
Identify the effect which is being demonstrated.
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(1)
(b)
A teacher makes some changes to the set-up of the demonstration.
What effect, if any, will each of the following changes have?
(i)
more powerful horseshoe magnet is used.
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(1)
(ii)
The connections to the power supply are reversed.
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(1)
(Total 3 marks)
Q15.
A student investigates the electromagnetic force acting on a wire which carries an electric
current. The wire is in a magnetic field.
The diagram shows the circuit which the student uses.
(a)
Draw an X on the diagram, with the centre of the X in the most strongest part of the
magnetic field.
(1)
(b)
Give one change that she can make to the magnets to decrease the electromagnetic
force on the wire.
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(1)
(c)
The student wants to change the electromagnetic force on the wire without changing the
magnets or moving their position.
(i)
Give one way in which she can increase the electromagnetic force.
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(1)
(ii)
Give one way in which she can reverse the direction of the electromagnetic force.
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(1)
(Total 4 marks)
Q16.
(a) A science technician sets up the apparatus shown below to demonstrate the motor
effect. He uses a powerful permanent magnet.
The copper roller is placed across the metal rails. When the switch is closed, the copper
roller moves to the right.
(i)
Complete the sentence by drawing a ring around the correct line in the box.
an electrical conductor.
This happens because copper is
an electrical insulator.
a magnetic material.
(1)
(ii)
Suggest one change that the technician can make which will cause the copper roller
to move faster.
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(1)
(iii)
Suggest two changes which the technician can make, each of which will separately
cause the copper roller to move to the left.
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(2)
(b)
Many electrical appliances, such as vacuum cleaners, drills and CD players, contain
electric motors. As more electrical appliances are developed, more electricity needs to be
generated. Generating electricity often produces pollutant gases.
(i)
Complete the sentence by drawing a ring around the correct line in the box.
Generating more electricity to power the increasing number of electrical appliances
used
an ethical
raises an environmental
issue.
a political
(1)
(ii)
The number of electrical appliances used in the world’s richest countries is
increasing yet many people in the world’s poorest countries have no access to
electricity.
What type of issue does this inequality between people in different countries raise?
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(1)
(Total 6 marks)
Q17.
(a) Complete the description of the device shown below by drawing a ring around the
correct line in each box.
an electric
motor.
(i) The device is being used as
a generator.
a transformer.
(1)
(ii)
The coil needs a flick to get started. Then one side of the coil is pushed by the
cell
coil
and the other side is pulled, so that the coil spins.
force
(1)
(b)
Suggest two changes to the device, each one of which would make the coil spin faster.
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2 ......................................................................................................................
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(2)
(c)
Suggest two changes to the device, each one of which would make the coil spin in the
opposite direction.
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(2)
(Total 6 marks)
Q18.The diagram shows a device called a current balance.
(a)
(i)
When the switch is closed, the part of the wire labelled XY moves upwards.
Explain why.
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(2)
(ii)
What is the name of the effect that causes the wire XY to move?
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(1)
(iii)
An alternating current (a.c.) is a current which reverses direction. How many times
the current reverses direction in one second depends on the frequency of the
alternating supply.
Describe the effect on the wire XY if the battery is replaced by an a.c. supply having
a frequency of 5 hertz.
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(2)
(b)
The diagram shows how a small weight can be used to make the wire XY balance
horizontally.
Use the data in the diagram and the equation in the box to calculate the force, F, acting on
the wire XY.
moment
=
force
×
perpendicular distance from the line of
action of the force to the axis of rotation
Show clearly how you work out your answer.
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Force = ............................................................ N
(3)
(Total 8 marks)
Q19.The diagram shows a student’s design for a simple wind speed gauge.
(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. .....................................................
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(3)
(b)
The gauge is not sensitive enough to measure light winds.
Suggest one way that the design can be modified to make the gauge more sensitive.
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(1)
(Total 4 marks)
Q20.A student has made a simple electric motor. The diagram shows the electric motor.
(a)
Complete the following sentence by drawing a ring around the correct line in the box.
the cell
Once the coil is spinning, one side of the coil is pushed by
the coil
and the other
a force
side is pulled, so the coil continues to spin.
(1)
(b)
Suggest two changes to the electric motor, each one of which would make the coil spin
faster.
1 .....................................................................................................................
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2 .....................................................................................................................
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(2)
(c)
Suggest two changes to the electric motor, each one of which would make the coil spin in
the opposite direction.
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(2)
(Total 5 marks)
Q21.The diagram shows a ‘G-machine’. The G-machine is used in astronaut training.
The G-machine moves the astronaut in a horizontal circle.
(a)
When the G-machine is rotating at constant speed, the astronaut is accelerating.
State the name and direction of the force causing the astronaut to accelerate.
Name of force ................................................................................................
Direction of force ...........................................................................................
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(2)
(b)
The force causing the astronaut to move in a circle is measured.
The graph shows how the speed of the astronaut affects the force causing the astronaut
to move in a circle for two different G-machines.
The radius of rotation of the astronaut is different for each G-machine.
Speed in metres per second
(i)
State three conclusions that can be made from the graph.
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(3)
(ii)
The speed of rotation of G-machine 1 is increased from 20 m/s to 40 m/s.
Determine the change in force on the astronaut.
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Change in force = ............................................................ N
(1)
(c)
Each G-machine is rotated by an electric motor. The diagram shows a simple electric
motor.
(i)
A current flows through the coil of the motor.
Explain why side A of the coil experiences a force.
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(2)
(ii)
Draw arrows on the diagram to show the direction of the forces acting on side A of
the coil and side C of the coil.
(1)
(iii)
When horizontal, side B experiences no force.
Give the reason why.
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(1)
(d)
While a G-machine is rotating, the operators want to increase its speed.
What can the operators do to make the G-machine rotate faster?
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(1)
(e)
The exploration of space has cost a lot of money.
Do you think spending lots of money on space exploration has been a good thing?
Draw a ring around your answer.
Yes
No
Give a reason for your answer.
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(1)
(Total 12 marks)
Q22.The diagram shows a ‘G-machine’. The G-machine is used in astronaut training.
The G-machine moves the astronaut in a horizontal circle.
(a)
In which direction, A, B or C, does the centripetal force on the astronaut act?
Write your answer in the
box.
(1)
(b)
The centripetal force on the astronaut is measured.
Graph X shows how the centripetal force is affected by the speed of rotation.The radius of
rotation is kept the same.
Speed of rotationin metres per second
(i)
Use Graph X to determine the centripetal force on the astronaut when rotating at a
speed of 30 metres per second.
Centripetal force = .............................. newtons
(1)
(ii)
Complete the following sentence to give the conclusion that can be made
fromGraph X.
Increasing the speed of rotation of a G-machine will ................................................
the centripetal force on the astronaut.
(1)
(iii)
Graph Y shows how the centripetal force is affected by the radius of rotation, when
the speed of rotation is kept the same.
Radius of rotationin metres
Complete the following sentence to give the conclusion that can be made
fromGraph Y.
The greater the radius of rotation, the ......................................... the centripetal force
on the astronaut.
(1)
(c)
The G-machine is rotated by an electric motor. The diagram shows a simple electric
motor.
The following statements explain how the motor creates a turning force. The statements
are in the wrong order.
M – The magnetic field interacts with the magnetic field of the permanent magnets.
N – A magnetic field is created around the coil.
O – The power supply applies a potential difference across the coil.
P – This creates a force that makes the coil spin.
Q – A current flows through the coil.
Arrange the statements in the correct order. Two of them have been done for you.
(2)
(d)
The electric motor produces a turning force.
Give two ways of increasing the turning force.
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(2)
(e)
Draw a ring around the correct answer to complete the sentence.
It costs a lot of money to send astronauts into space.
an economic
This
is
an environmental
issue.
a social
(1)
(Total 9 marks)
Q23.(a)
Some people wear magnetic bracelets to relieve pain.
Figure 1 shows a magnetic bracelet.
There are magnetic poles at both A and B.
Part of the magnetic field pattern between A and B is shown.
Figure 1
What is the pole at A? ...........................................
What is the pole at B? ...........................................
(1)
(b)
Figure 2 shows two of the lines of the magnetic field pattern of a current-carrying wire.
Figure 2
The direction of the current is reversed.
What happens to the direction of the lines in the magnetic field pattern?
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(1)
(c)
Fleming’s left-hand rule can be used to identify the direction of a force acting on a currentcarrying wire in a magnetic field.
(i)
Complete the labels in Figure 3.
Figure 3
(2)
(ii)
Figure 4 shows:
•
the direction of the magnetic field between a pair of magnets
•
the direction of the current in a wire in the magnetic field.
Figure 4
In which direction does the force on the wire act?
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(1)
(iii)
Suggest three changes that would decrease the force acting on the wire.
1 ..........................................................................................................
2 ..........................................................................................................
3 ..........................................................................................................
(3)
(d)
Figure 5 shows part of a moving-coil ammeter as drawn by a student.
The ammeter consists of a coil placed in a uniform magnetic field.When there is a current
in the coil, the force acting on the coil causes the coil to rotate and the pointer moves
across the scale.
Figure 5
(i)
The equipment has not been set up correctly.
What change would make it work?
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(1)
(ii)
Figure 6 shows the pointer in an ammeter when there is no current.
Figure 6
What type of error does the ammeter have?
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(1)
(Total 10 marks)
M1.
Quality of written communication: One mark for correct sequencing.bolt out  plunger
up  switch off / circuit broken
1
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
[6]
M2.
electromagnet becomes stronger (not becomes magnetic) iron moves left – implied OK
plunger goes up push switch goes to off or circuit broken unless plunger moves down
for 1 mark each
[4]
M3.
(a) current flows
coil / core magnetised / electromagnet activated / energised / turned on
attracts iron bar causing bolt to be pulled out
each for 1 mark
4
(b)
more turns
bigger current / e.m.f
softer iron core
any two for 1 mark each
2
(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
yes + wrong answer
0 marks
yes + current still flows
1 mark
yes + still magnetised / iron bar still attracted
2 marks
2
[9]
M4.
(a)
(i)
it moves or experiences a force horizontally to the right
for 1 mark
1
(ii)
A – moves in opposite direction or force reversed e.c.f.
B – faster movement or larger force
(not move further)
for 1 mark each
2
(b)
turns clockwise
oscillates/reverses
comes to rest facing field/at 90o to field/vertically
for 1 mark each
3
(c)
number of turns or linear number density of turns current core
for 1 mark each
3
[9]
M5.
(i)
relay
accept solenoid
do not accept magnetic switch
1
(ii)
a current flows through the coil (of the electromagnet)or a current flows through the
electromagnetor 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
1
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]
M6.
(i)
away from magnet
arrow should be perpendicular to field lines and current as judged
by eye
1
(ii)
current in wire creates magnetic field around wire
1
two fields interact or combine giving a resultant force (on the wire)
1
[3]
M7.
(a)
plastic or rubber
accept any named plastic
do not accept wood
1
it is a (good) insulator or it is a poor conductor
ignore mention of heat if in conjunction with electricity
1
(b)
The answer to this 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.
Maximum of 2 marks if ideas not well expressed.
pulls iron bolt down or attracts the iron bolt or moves bolt out of plunger
answers in terms of charges attractingor repelling gain no credit
1
plunger pushed / moved to the right (by spring) or plunger released
1
push switch opens / goes to off / goes to right
accept circuit is broken
for maximum credit the points must follow a logical sequence
3 correct points but incorrect sequence scores 2 marks only
ignore reset action
1
[5]
M8.
(a)
step-down (transformer)
1
(b)
alternating current
accept minor misspellings but
do not credit ‘alternative current’
1
(c)
(i)(ii) magnet
attracts
upwards
correct order essential
accept ‘up’
3
[5]
M9.
(a)
increase the current (1)
credit increase the p.d./voltage
credit reduce the resistance
credit have thicker wiring
credit add extra / more cells
1
increase the magnetic field (strength) (1)
credit ‘have stronger magnet(s)
do not credit ‘bigger magnets’ either order
1
(b)
either reverse polarity
or connect the battery the other way round
1
either reverse direction of the magnetic field
or put the magnet the other way round / reverse the magnet
do not give any credit to a response in which both are done at the
same time
either order
1
(c)
either
conductor parallel to the magnetic field
or lines of magnetic force and path of electricity do not cross
1
[5]
M10.
(a)
electric drill, electric fan, electric food mixer and electric screwdriver
all four ticked and no others (2)
either all four of these ticked and only one other (1)
or any three of these ticked and none/one/two of the others (1)
2
(b)
(i)
reverse (the direction of the) current (1)
or reverse the connections (to the battery)
reverse (the direction of the) magnetic field (1)
or reverse the (magnetic) poles /ends
do not credit ‘swap the magnets (around)’
2
(ii)
any two from:
•
increase the strength of the magnet(s)/(magnetic) field
do not credit ‘use a bigger magnet’
•
increase the current
allow ‘increase the voltage/p.d.’allow add cells/batteriesallow
increase the (electrical) energyallow increase the power
supplyallow ‘decrease the resistance’allow ‘increase charge’allow ‘
increase the electricity’
do not credit ‘use a bigger battery’
•
reduce the gap (between coil/armatureand poles/magnets)
allow increase the (number of) coils
•
increase the turns (on the coil/armature)
do not credit ‘use a bigger coil’
2
[6]
M11.(a)
correct symbol identified
1
(b)
because both I and n are changing
1
it could be either I or n that affect W
or
it could be both I and n that affect W
if no other marks awarded allow 1 mark for one needs to be
controlled
or
must only have one independent variable
1
(c)
for all values of n weight supported increases with increasing current
accept for 1 mark, weight supported increases with increasing
current
2
but not linearly
1
for a given current the weight supported increases with increase in n
1
weight supported reaches a maximum with n = 30 turns
1
(d)
2.3 (A)
accept any value between 2.3 and 2.4
1
(e)
(i)
there is a current in the electromagnet
accept electromagnet is switched on
1
the electromagnet attracts the iron arm
1
the arm pivots and pushes the contacts together
accept closes the switch
1
resulting in a current in the (starter) motor circuit
1
(ii)
electrical energy is supplied to the motor, and not all of this energy is usefully
transferred to kinetic energy
1
some of the energy is wasted as thermal energy, (and sound energy)
1
therefore (useful energy out divided by / total energy in) is less than 100%
1
[16]
M12.
Marks awarded for this answer will be determined by the Quality of Written
Communication (QWC) as well as the standard of the scientific response.
No relevant content.
0 marks
There is a brief explanation of how a current is caused to flow in the
starter motor circuit.
Level 1 (1–2 marks)
There is some explanation of how a current is caused to flow in the
starter motor circuit.
Level 2 (3–4 marks)
There is a clear and detailed explanation of how a current is caused
to flow in the starter motor circuit.
Level 3 (5–6 marks)
examples of the physics points made in the response
current flows through the coil / electromagnet
magnetic field produced
accept electromagnet switches on
(short side of) iron bar attracted to electromagnet
contacts pushed together (by iron bar)
starter motor circuit completed
current flows through starter motor
or
p.d. across starter motor
[6]
M13.
(a)
so the results can be compared fairly
fair test is insufficient
1
(b)
JLM
all 3 required and no other
1
(c)
(i)
for a given current the number of paper clips increases
by the same factor as the number of turns
1
plus a mathematical explanation using the data
eg a current of 1 A with 10 turns picks up 3 clips, a
current of 1 A with 20 turns picks up 6 clips
1
(ii)
30
allow 1 mark for showing correct use of figures eg
20 turns × 5 = 100 turns
2
(iii)
check the new data / repeat the experiment
1
to identify any anomalous results
1
then reconsider prediction / hypothesis in thelight of new evidence
1
[9]
M14.
(a)
motor (effect)
1
(b)
(i)
wire kicks further (forward)
accept moves for kicks
accept moves more
accept ‘force (on the wire) increased’
1
(ii)
wire kicks back(wards) / into (the space in) the (horseshoe) magnet
accept moves for kicks
accept ‘direction of force reversed’
1
[3]
M15.
(a)
centre of the X midway between the poles
intention correct as judged by eye
example
1
(b)
move the poles further apart
accept turn for move
accept ends / magnets for poles
accept use weaker magnets
do not accept use smaller magnets
1
(c)
(i)
add more cells (to the battery)
do not accept ‘use a bigger battery’
accept increase the potential difference / voltage
accept increase the current
or
reduce the resistance (of the variable resistor)
do not accept any changes to the magnets, to the wire or to their
relative positions
1
(ii)
reverse (the polarity of) the battery
accept turn the battery / cells round
accept swap the connections to the battery
do not accept any changes to the magnets, to the wire or to their
relative positions
1
[4]
M16.
(a)
(i)
an electrical conductor
1
(ii)
increase current
accept increase p.d. / voltage
or
use stronger magnets
accept move magnets closer
do not accept use larger magnets
1
(iii)
reverse the poles / ends (of the magnet)
either order
1
reverse the connections (to the power supply)
1
(b)
(i)
environmental
1
(ii)
ethical
allow political (instability)
allow economic (migration)
1
[6]
M17.
(a)
(i)
an electric motor
1
(ii)
force
1
(b)
any two from:
•
more powerful magnet
do not allow ‘bigger magnet’
•
reduce the gap (between magnet and coil)
•
increase the area of the coil
•
more powerful cell
do not allow ‘bigger cell’
accept battery for cell
accept add a cell
accept increase current / potential difference
•
more turns (on the coil)
allow ‘more coils on the coil’
do not allow ‘bigger coil’
2
(c)
reverse the (polarity) of the cell
allow ‘turn the cell the other way round’
accept battery for cell
1
reverse the (polarity) of the magnet
allow ‘turn the magnet the other way up’
1
[6]
M18.
(a)
(i)
current produces a magnetic field (around XY)
accept current (in XY) is perpendicular to the (permanent)
magnetic field
1
(creating) a force (acting) on XY / wire / upwards
reference to Fleming's left hand rule is insufficient
1
(ii)
motor (effect)
1
(iii)
vibrate / move up and down
1
5 times a second
only scores if first mark point scores
allow for 1 mark only an answer ‘changes direction 5 times a
second’
1
(b)
0.005
allow 1 mark for calculating moment of the weight as 0.04 (Ncm)
and
allow 1 mark for correctly stating principle of moments
or
allow 2 marks for correct substitution
ie F × 8 = 2 × 0.02 or F × 8 = 0.04
3
[8]
M19.(a)
which causes the magnet to turn / spin / rotate
1
(magnetic) field / lines of force / flux rotate(s) / move(s) / through / in / cut(s) the coil
do not credit the idea that movement ‘creates’ the magnetic field
1
potential difference / p.d. / voltage induced across the coil
do not credit just ‘current induced’
1
(b)
any one from:
•
more powerful / stronger / lighter magnet
do not credit ‘a bigger magnet’
•
larger / more / bigger / lighter cups / with a bigger surface area
•
longer arms
•
lubricate the spindle
•
add more turns to the coil
1
[4]
M20.(a)
a force
1
(b)
any two from:
•
more powerful magnet
do not allow ‘bigger magnet’
•
reduce the gap (between magnet and coil)
•
increase the area of the coil
•
more powerful cell
do not allow ‘bigger cell’
accept battery for cell
accept add a cell
accept increase current / potential difference
•
more turns (on the coil)
allow ‘more coils on the coil’
do not allow ‘bigger coil’
2
(c)
reverse the (polarity) of the cell
allow ‘turn the cell the other way round’
accept battery for cell
1
reverse the (polarity) of the magnet
allow ‘turn the magnet the other way up’
1
[5]
M21.(a)
centripetal (force)
allow tension (between astronaut and seatbelt)
1
towards the centre (of the G-machine / circle)
do not accept towards the centre of the Earth
allow inwards
1
(b)
(i)
the greater the speed (of a centrifuge), the greater the force
answers must be comparative
accept velocity for speed
accept positive correlation between speed and force
speed and force are not proportional – treat as neutral
1
the smaller the radius, the greater the force (at a given speed)
allow (G machine) 1 has / produces a greater force (than
G machine 2 ) at the same speed
must be comparative, eg a small radius produces a large force = 0
marks on own
1
as the speed increases the rate of change in force increases
accept force is proportional to the square of the speed
or
doubling speed, quadruples the force
accept any clearly correct conclusion
1
(ii)
12000 (N)
or
12 k(N)
1
(c)
(i)
the current (in the coil) creates a magnetic field (around the coil)
accept the coil is an electromagnet
1
so the magnetic field of the coil interacts with the (permanent) magnetic field
of the magnets (producing a force)
accept the two magnetic fields interact (producing a force)
if no marks scored an answer in terms of current is perpendicular
to the (permanent) magnetic field is worth max 1 mark
1
(ii)
vertically downwards arrow on side A
one arrow insufficient
and
vertically upwards arrow on side C
1
(iii)
the current is parallel to the magnetic field
allow the current and magnetic field are in the same direction
allow it / the wire is parallel to the magnetic field
1
(d)
increase the current / p.d. (of the coil)
accept decrease resistance
accept voltage for p.d.
accept increase strength of magnetic field / electromagnet
1
(e)
yes with suitable reasonorno with suitable reason
eg
yes – it has increased our knowledge
yes – It has led to more (rapid) developments / discoveries (in
technology / materials / transport) accept specific examples
no – the money would have been better spent elsewhere on such
things as hospitals (must quote where, other things not enough)
no mark for just yes / no
reason must match yes / no
1
[12]
M22.(a)
A
1
(b)
(i)
9000
an answer of 9 k(N) gains 1 mark
1
(ii)
increase
accept other comparative terms, eg give a bigger
affect / change is insufficient
1
(iii)
smaller
accept other comparative terms, eg less
1
(c)
QNM
all three in correct boxes
one statement in correct box gains 1 mark
2
(d)
any two from:
•
increase the current / p.d. (supplied to the coil)
accept reduce the resistance of the coil or increase cross sectional
area of wire
accept more cells / batteries or turn up the power supply
increase power is insufficient
•
increase number of turns (on the coil)
•
increase the area (of the coil)
accept increase the width of the coil
increase width / size is insufficient
•
increase the (strength of the permanent) magnetic field
accept move the magnets closer to the coil
accept use stronger magnets
do not accept use larger magnets
2
(e)
an economic
1
[9]
M23.(a)
north (pole)
accept N
north (pole)
both needed for mark
1
(b)
reverses
accept changes direction
1
(c)
(i)
first finger:
(direction of) (magnetic) field
1
second finger:
(direction of) (conventional) current
1
(ii)
into (plane of the) paper
1
(iii)
less current in wire
accept less current / voltage / more resistance / thinner wire
1
weaker field
allow weaker magnets / magnets further apart
do not accept smaller magnets
1
rotation of magnets (so) field is no longer perpendicular to wire
1
(d)
(i)
reverse one of the magnets
do not accept there are no numbers on the scale
1
(ii)
systematic or zero error
accept all current values will be too big
accept it does not return to zero
accept it does not start at zero
1
[10]
E1.
Foundation Tier
Most candidates gained some credit on this question, with the better candidates producing very
good descriptions. Some chose simply to describe what they could see in the two diagrams
rather than describe the sequence of events that would cause the circuit to break. Incorrect
ideas that were frequently seen were that, ‘the coils heat up’, ‘the springs pass the current’ or
‘the button must be pressed to switch off the electricity’. Very few candidates understood that as
a consequence of an increased current the electromagnetic attraction increases and attracts the
iron bolt.
Higher Tier
Most candidates gained credit on this question, with the better candidates producing very good,
detailed descriptions. Some weaker candidates chose simply to describe what they could see in
the two diagrams rather than describe the sequence of events that would cause the circuit to
break. There were, however, only a few candidates who understood that as a consequence of
an increased current, the electromagnetic attraction increases and attracts the iron bolt.
E2.
The weaker candidates found difficulty in gaining marks, their writing was not coherent and
lacking in relevant detail. Of the more able candidates a surprisingly large number had clearly
studied the diagram, worked out how it worked and then offered reasonably precise answers to
gain three or four of the marks.
E4.
In part (a)(i) very many candidates had the wire moving, unfortunately in many cases the
movement was up or down. Few candidates stated that the wire would move along the copper
wires to the right. In part (ii) many had the movement reversed, but reversing an up/down
movement does not give a correct answer only answers stating that the wire would move to the
left were acceptable. In the last part of the question a faster movement was the common correct
answer. In part (b) candidates seemed to be familiar with the electric motor but experienced
difficulty in applying their ideas in an unfamiliar situation. Most candidates started their answer
with a clockwise movement for one mark, fewer went on to say the coil would then vibrate
backwards and forwards for the second mark. The final mark, for stating (in their own words)
that the coil would end up perpendicular to the field, was gained by a small number of
candidates. Part (c) was quite well answered with most candidates scoring marks for increasing
the number (or number density) of turns and the current. many went on to gain the third mark
for the use of a soft iron core.
E5.
Foundation Tier
This question was poorly answered. In this question few could name the switch or explain the
operation of a relay in the car starter motor circuit. Common errors included the belief that the
electromagnet became ‘charged’ or that a current would flow from the coil to the iron arm and
subsequently into the motor.
Higher Tier
In part (i) many candidates were unable to name the switch as a relay. In part (ii) many
candidates were able to explain the process by which the car starter ignition system worked,
although the precision of the answers was sometimes poor. A significant minority of candidates
seemed to think that the iron arm would conduct electricity into the motor circuit.
E6.
In part (a)(i) the better candidates gave the correct direction of movement, however, many
suggested the wire would oscillate back and forth. Part (a)(ii) was very poorly done. Only a very
small number of candidates mentioned the magnetic field created by the current and even fewer
indicated any interaction between the fields. Many candidates seemed to interpret the question
as ‘how do you work out where the wire moves?’
E7.
Foundation Tier
The responses in part (a) was mostly worthy of credit.
(b)
There were abundant clues in both the stem of the question and the labels on the diagram
to start candidates on the correct sequence. However, rather too many candidates started
their answers with the iron bolt moving upwards with the result that they were unable to
logically explain the working of the circuit breaker.
Higher Tier
This question was particularly well answered by most candidates.
(a)
Most candidates gained both marks in this part but some gave heat insulation and failed
to mention electrical insulation.
(b)
E8.
There were some excellent answers to this part but a minority of candidates were unable
to explain how this type of circuit breaker works.
(a)
A third of candidates gained the mark by recognising the correct transformer.
(b)
A third of candidates knew that a.c. stands for alternating current.
(c)
(i)
Most candidates recognised that when a current flows in a coil, the coil becomes a
magnet.
(ii)
Two thirds of candidates gained both marks by recognising that the coil attracts the
iron bolt which moves upwards.
(a) Most candidates chose ‘increase the current’ or a correct way of doing this, such as to
increase the p.d. or increase the number of cells, and some also suggested ‘have a
stronger magnet’. However writing ‘have a bigger magnet’ did not gain credit as a bigger
magnet would not necessarily be stronger and the poles could be further from the
conductor.
E9.
(b)
Some candidates correctly suggested that the battery would need to be connected the
other way round or that the magnet would need to be put the other way round. However
some answers were so poorly expressed that it was impossible to be reasonably sure
what was being suggested.
(c)
Few candidates knew that there would be no force on the conductor when the conductor
is parallel to the magnetic field or, put another way, when the lines of magnetic force and
the path of the electricity do not cross.
E10.
(b)
(a)
A large majority of the candidates chose the correct four appliances from the list.
(i)
The responses in part (b) were generally poor with only a minority able to gain a
mark in (b)(i) with a similar, though improved, outcome in part (b)(ii).
(ii)
Candidates should be advised that although ‘use more cells in the battery’ is correct
in part (b)(ii) the ambiguous ‘use a bigger battery’ is not.For similar reasons the
vague responses of ‘use bigger magnets’ and ‘use a bigger coil’ were not awarded
marks.
E14.
(a)
(b)
E15.
Under half of candidates were able to name the effect being demonstrated.
(i)
The majority of candidates managed a correct response, although a number of
responses needed to be read through a few times as ideas were not expressed
clearly.
(ii)
The majority of responses were correct.
(a) & (b) Nearly all candidates were able to do the first two items.
(c) (i) & (ii) Many candidates failed to read this correctly and gave answers in terms of magnets
which had been precluded in the first sentence of the item. Only a quarter of
candidates gained the mark in (c)(i), and even fewer obtained the mark for (c)(ii).
E16.
(a)
(b)
(i) Although over half of candidates knew that the experiment worked because
copper is an electrical conductor, just under half of candidates thought it was
because copper is a magnetic material.
(ii)
Nearly three quarters of candidates were able to describe an acceptable way to
increase the speed of the copper roller. However in this question and the next many
candidates suggested tilting the rails to achieve the desired effect.
(iii)
Candidates lost marks in this question by not explaining clearly enough what they
meant, for example several mentioned moving the battery to the other side without
mentioning reversing the current or the connections and there were many incorrect
answers relating to the switch. However, more than two fifths of candidates gained
at least one mark. The most common correct answer related to reversing the
magnetic field in some way.
(i)
This was well answered with nearly all candidates gaining the mark.
(ii)
This was well answered with nearly two thirds of candidates giving the correct type
of issue.
E17.
(a)
(ii)
(i) Candidates continue to have difficulty in identifying electromagnetic devices.
However, half of the candidates correctly identified the motor, whilst a third of
candidates thought it was a generator and a small minority of candidates a
transformer.
Nearly three-quarters of candidates identified the force exerted as being the cause
of the spin.
(b)
A number of candidates wrote down what needed to be changed but often not how they
should be changed ie ‘change the number of turns on the coil’ rather than ‘increase the
number of turns on the coil’ and so failed to gain credit. Candidates continue to use
inappropriate adjectives eg ‘bigger’ magnets rather than ‘stronger’ magnets.
(c)
Only a fifth of candidates could give two correct changes. Again poor / inappropriate use
of language stopped many candidates gaining any marks.
E18.
(a)
(b)
E19.(a)
(i)
Students rarely included the idea of the current producing a magnetic field
around the wire XY. Some students were clearly confused with the induction
process.
(ii)
Just over half of students scored this mark.
(iii)
Just over half of students scored at least one mark. Incorrect responses included:
back and forth; spinning; faster; repelled instead of ‘up and down’. The frequency of
5 hertz was sometimes interpreted as once every five seconds.
There was a clear distinction in this question between the students who could do the
calculation perfectly and those who struggled. Some answers were left as fractions by
students without calculators; there were a number of 1 mark responses for calculating the
left hand moment. A number of students did not gain marks because of inconsistent units
and moving between cm and m.
Half the students gained only one mark, often for the “spinning” of the magnet.
There was little sequencing of the generator effect.
(b)
Nearly three quarters of students gained the mark. Of the remainder, there were still many
responses referring to “bigger” magnets rather than ‘stronger magnets’ and “more coils”
rather than ‘more turns on the coil’.
E20.Nearly three quarters of students answered part(a) correctly. In (b)&(c), although better answered
than in previous series, students continue to have difficulties describing accurately what
changes need to be made to a motor to cause different effects. Some still only state what needs
to be changed without specifying in what way it is changed, in many of the answers the
descriptions were too vague to merit a mark.
E21.(a)
(b)
(c)
The majority of candidates gained both marks on this question. Common errors were
“centrifugal” or “centripedal”.
(i)
Very few candidates scored all 3 marks, but half of the candidates scored 2. Some
mistakenly stated that force changed the speed, rather than understanding that the
speed of rotation affected the centripetal force on the astronaut.
(ii)
Two thirds of candidates calculated the correct answer.
(i)
The majority of responses gained a mark of zero. Use of correct terminology, e.g.
the permanent magnetic field interacting with the magnetic field produced by the
current, should be stressed to candidates.
(ii)
Only a quarter of candidates gained this mark where Fleming’s Left Hand Rule had
to be applied. Some failed to gain the mark as they drew in how the coil would
rotate, rather than the direction of the forces.
(iii)
A quarter of candidates gained this mark. There were a lot of incorrect answers
showing the misconception that the upwards and downward forces were equal and
opposite.
(d)
Two thirds of candidates gained this mark. Of the candidates who did not score, many
failed to realise that what was required was an immediate change that the operators could
make, or were too brief with their answer “increase the supply”.
(e)
This question tested the societal aspects of scientific evidence. Many coherent answers
were produced, with the majority of the responses gaining the mark. At times answers
were too brief, “the money would be better spent elsewhere”, rather than stating exactly
where (e.g. medical care / hospitals). Some answers looked at possible future benefits,
rather than the benefits achieved so far.
E22.(a)
Half of the candidates correctly identified the direction of the centripetal force.
(b)
The vast majority were able to score all the marks in (b)(i), (b)(ii) and (b)(iii).
(c)
About two thirds of candidates correctly placed all three letters; but a significant minority
failed to gain marks here.
(d)
Around half the candidates scored both marks, but a common mistake was referring to the
power supply rather than an increase in p.d. or current. Some candidates failed to score
by referring to the use of ‘bigger’ magnets or a ‘bigger’ magnetic field.
(e)
E23.(a)
The vast majority of candidates gained this mark.
Just over half of the students knew that a magnetic field of repulsion between two poles
with lines of force moving outward from the poles was that between two north poles.
(b)
Nearly all students knew that reversing the current through a wire also reversed the
direction of the field lines associated with it.
(c)
(i)
Three-quarters of students knew which directions the first two fingers represent in
Fleming’s left-hand rule.
(ii)
Students were given a diagram of a wire carrying a current in a magnetic field. Using
Fleming’s left-hand rule the wire would move into the paper. Many students were
able to use the rule successfully, but their answers were ambiguous, such as
‘downwards’ and ‘away from you’. Less than a fifth of students scored the mark.
(iii)
Over three quarters of the students knew that decreasing the current and the
strength of the magnetic field would decrease the force acting on the wire. Only a
tenth of the students knew that rotating the magnets so that the field was no longer
perpendicular to the wire would also have the same effect.
(i)
Most students observed that two south poles facing each other would not give a
uniform magnetic field and suggested that one of the magnets should be rotated.
(ii)
Less than three quarters of students knew that an ammeter pointing to a value
above zero when no current was in it, had a systematic or zero error.
(d)