Download Motors and Generators #2

1 Current Carrying Conductors
1.1
Discuss the effect on the magnitude of the force on a current carrying conductor of variations in certain
properties:

Formula:
F = BILsinθ
F = Force (N)
B = Magnetic field strength (T)
I = Current (A)
L = Length of the conductor (m)
θ = Angle of the conductor to the magnetic field

Strength of the Magnetic Field:
o Force is proportional to the strength of the magnetic field
o Stronger magnetic field, greater force on conductor

Magnitude of Current in Conductor:
o Increasing current means increasing the velocity of the electrons
o Each moving charged particle experiences a force in proportion to its velocity

Length of Conductor:
o The longer the section of conductor in a magnetic field, the more moving electrons simultaneously
experience a force
o Force is proportional to the length within the magnetic field
o Shorter length, smaller force on conductor

Angle between direction of magnetic field and conductor:
o Force is strongest when particle is moving at right angles to the magnetic field (90°)
o Force is zero when particle is moving parallel to the magnetic field (0°)
o Movement of electrons is along a length of conductor, magnitude of force varies with angle between
conductor and magnetic field
o As angle increases, force increases
2.1
Describe qualitatively the force between long parallel current carrying conductors:

Force between parallel conductors exists because magnetic fields due to current flowing through the
conductors interact with each other.
Direction of Force (Attraction or Repulsion):
 Depends on relative directions of the two currents
 Currents flowing in the same direction, attractive force, towards each other
 Currents flowing in opposite direction, repulsive force, away from each other
Magnitude of Force:
 Depends on magnitude of current within wire
 Increases or decreases with the product of the two currents
 Also depends on distance of separation between the conductors
 Increasing as the conductors are moved closer together
Relation to Length:
 Force between conductors depends on length of parallel conductors
 Larger for longer conductors
 "Force per unit length" - varies only with magnitude of the two currents and the distance between them.
Formula:
F
l
k
I1I2
d
F = Force (N)
l = Length of parallel conductors (m)
I1 & I2 = Currents in the conductors (A)
d = Distance between the conductors (m)
k = constant (2.0x10-7)
Page | 1
Define torque as the turning moment of a force:
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Turning force or turning moment of a force
Increased by increasing the applied force or perpendicular distance
Formula:
τ = Fd
τ = Torque (Nm)
F = Applied force perpendicular to axis of rotation (N)
d = Perpendicular distance between ‘line of action’ and pivot (m)
3.2
Describe the forces experienced by a current-carrying loop in a magnetic field and describe the net result of
the forces:
Forces on the sides ab and cd:
 Experience maximum force since the current in them is perpendicular to the magnetic field
 Magnitude of the force does not change throughout its rotation
 Using the right hand palm rule, the direction of the force on sides ab and cd can be deduced
 The net result of these two forces is to produce a torque on the loop about the axis; in the diagram above, the
torque is acting in an anticlockwise direction
Forces on the sides bc and ad:
 The sides of the loop, ad and bc, experience no force because the current is parallel to the magnetic field

Magnitude of the force varies from zero to maximum
o Zero when the plane of the coil is parallel to the magnetic field (i.e. as above)
o Maximum when the plane of the coil is perpendicular to the magnetic field
Net torque:
 Maximum when the plane of the coil is parallel to the magnetic field (i.e. as above)
 Direction alternates through a complete rotation
 Current-carrying loop orientated in a plane at right angles to a magnetic field will experience no net force
Formula:
τ = nBIAcosθ
τ = Torque (Nm)
n = number of turns/loops of the coil
B = Magnetic field strength (T)
I = Current flowing through the loop (A)
A = Area of the loop (m2)
θ = Angle between the plane of the loop and the field
Page | 2
3.3
Identify that the motor effect is due to the force acting on a current carrying conductor in a magnetic field:
Force on a Current-Carrying Conductor – The Motor Effect:
 Motor effect- The force experienced when a current carrying conductor moves through a magnetic field. This
force is produced because of the interaction between the magnet’s magnetic field and the current’s
electromagnetic field.
4.1
Describe the application of the motor effect in the galvanometer and the loudspeaker:
The Galvanometer:
 Device used to measure magnitude and direction of small DC
currents
The Motor Effect:
 When current flows through the coil, the coil experiences a
force due to the presence of the external magnetic field
 The iron core of coil increases the magnitude of this force
 Needle rotated until magnetic force on the coil is equalled
by a counter-balancing ‘restraining spring’. (torque)
 Scale of galvanometer is linear, amount of deflection
proportional to current flowing through coil.
The Loudspeaker:
 Device that transforms electrical energy into sound energy.
They consist of a circular magnet that has one pole on the
outside and one on the inside.
The Motor Effect:
 A current-carrying coil (voice coil) interacting with a permanent magnet
experiences a force as a result of the motor effect when a current is
present. The voice coil is connected to the amplifier.
 This force causes the coil to vibrate rapidly back-and-forth, in turn
making the speaker cone vibrate and send sound waves into the air.
 When the magnitude of the current increases, so too does the force on
the coil
 When the force on the coil increases, it moves more and the produced
sound is louder.
Page | 3
5.1
Describe the main features of a DC electric motor and the role of each feature & identify that the required
magnetic fields can be produced either by current-carrying coils or permanent magnets:
An electric motor is a device which converts electrical energy to useful mechanical energy (usually rotation)
Part
Description
Role of part
Pair of magnets
 Two permanent magnets on
 The magnets supply the magnetic
opposite sides of the motor,
field which interacts with the current
with opposite poles facing each
in the armature to produce the
other.
motor effect. The shape of the pole
faces makes the magnetic field
 The pole faces are curved to fit
almost uniformly radial where the
around the armature.
coil passes.
Pair of electromagnetic
 Each stator coil (or “field” coil)
 Each opposed pair of stator coils
coils
is wound on a soft iron core
produces a magnetic field similar to
attached to the casing of the
that provided by a pair of permanent
motor.
magnets. The iron core concentrates
the field.
 The coils are shaped to fit
around the armature.
Armature
 The armature consists of a
 The armature carries the rotor coils.
cylinder of laminated iron
The iron core greatly concentrates
mounted on an axle.
the external magnetic field,
increasing the torque on the
 Often there are longitudinal
armature. The laminations reduce
grooves into which the coils are
eddy currents which might
wound.
otherwise overheat the armature.
Rotor coils
 These are several turns of
 provide torque, as the current
insulated wire, wound onto the
passing through the coils interacts
armature.
with the magnetic field.
 The ends of the coils are
connected to bars on the
commutator.
Split ring commentator
 The commutator is a broad ring
 The commutator provides points of
of metal mounted on the axle at
contact between the rotor coils and
one end of the armature, and
the external electric circuit.
cut into an even number of

It serves to reverse the direction of
separate bars (two in a simple
current flow in each coil every halfmotor).
revolution of the motor. This
 Each opposite pair of bars is
ensures that the torque on each coil
connected to one coil.
is always in the same direction.
Brushes
 Compressed carbon blocks,
 Their position brings them into
connected to the external
contact with both ends of each coil
circuit, the brushes are the fixed
simultaneously, as each coil is
position electrical contacts
positioned at right angles to the
between the external circuit
field, to maximise torque.
and the rotor coils.
 This maximises torque.
 They are mounted on opposite
sides of the commutator and
spring-loaded to make close
contact with the commutator
bars.
Axle
 A cylindrical bar of hardened
 provides a centre of rotation for the
steel passing through the centre
moving parts of the motor.
of the armature and the
 Useful work can be extracted from
commutator.
the motor via a pulley or cog
mounted on the axle.
Page | 4
6.1 Outline Michael Faraday's discovery of the generation of an electric current by a moving magnet:
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7.1
After discovering that an electric current produces a magnetic field, in 1820, Faraday’s ideas about
conservation of energy led him to believe that since an electric current could cause a magnetic field, a moving
magnetic field should be able to produce an electric current.
In 1831, Faraday attached two wires through a sliding contact to touch a rotating copper disk located between
the poles of a horseshoe magnet. This induced a direct current and was the basis to an electric generator.
Faradays explanation was that an electric current can be induced by moving a conductor within the 2 poles of
a magnet as it cuts a number of lines of magnetic force coming from the magnet (the magnetic field). The
wires allowed the current to flow in an external circuit where it could be detected.
Define magnetic field strength (B) as magnetic flux density:
Representing Magnetic Fields:
 Magnetic flux lines 'flowing' out of the north pole and into the south pole
 Lines closer together near the poles where magnetic field is strongest
 Lines further apart at greater distances from the magnet
 Magnetic field of stronger magnet, larger number of magnetic flux lines
 Magnetic field of weaker magnet, smaller number of magnetic flux lines
Magnetic Flux Density:
 Measure of the number of magnetic flux lines passing through a unit area (1m2)
 Magnetic field strength at a point is the same as the magnetic flux density at that point
7.2
Describe the concept of magnetic flux in terms of magnetic flux density and area:
Magnetic Flux:
 Magnetic flux- Amount of magnetic field lines passing through a given area
 Represented diagrammatically as number of flux lines passing through the area
 The relationship of the magnetic flux is given by (Note: This formula is not required):
where
Φ = BA
Φ = the total magnetic flux (Wb)
B = magnetic field strength (T)
A = perpendicular area through which the flux passes (m2)
7.3
Describe generated potential difference as the rate of change of magnetic flux through a circuit:



The size of an induced EMF is directly proportional to the rate of change in magnetic flux
In order to induce an EMF, a changing magnetic flux is essential
The change in flux can be changed in an conductor by:
o moving the conductor or the magnetic field
o Changing the strength of the magnetic field.
o The speed of the relative motion between the magnetic field and the conductor
o The number of turns of coil or conductors
o The change in area that the magnetic field passes through

Formula:
ɛ=n
where
ΔΦ
Δt
ɛ = Potential difference (V)
n = Number of turns in the coil
Φ = Magnetic flux (Wb)
t = Time (seconds)
ΔΦ = Rate of change in magnetic flux
Δt
Page | 5
8.1
Account for Lenz's Law in terms of conservation of energy and relate it to the production of back EMF in
motors & explain that in electric motors, back EMF opposes the supply EMF:
Lenz’s Law:
 “The direction of any induced EMF will always be such that it opposes the change that caused it”
 To find the direction of an induced emf (or induced current) we apply the RHPR to the given situation and then
reverse the direction of the current flow
Conservation of Energy:
 The law of conservation of energy states: Energy
cannot be created or destroyed, it can only be
transformed or transferred
Consider a magnet moving into a Cylinder:
 By Lenz's law, work must be done to move magnet
into coil providing energy to induce EMF
 If Lenz's Law did not hold true, the magnet would be
accelerated into the coil – i.e. creating mechanical
energy with no input energy
 Thus, to obey the law of conservation of energy, the
induced current must flow to oppose the cause.
Back EMF:
 When an electric motor is first switched on, the
applied voltage produces a large current in the coils. When the coils begin to rotate, changing flux within coils
induces an emf; by Lenz's law, the induced emf is opposite to the emf applied to the motor and this is known as
the back emf.
8.2
Explain the production of eddy currents in terms of Lenz's Law:

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Eddy currents – the current produced by the back emf opposing current in the coil from a external source.
By Lenz's Law, eddy currents oppose the changing magnetic field producing them.
Eddy currents produce its own magnetic field which opposes the relative motion of the magnetic field which
created it.
9.1 Identify how eddy currents have been utilised in electromagnetic braking:
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Eddy currents have been utilised in the electromagnetic braking of free fall recreational rides.
A copper plate is attached to the bottom of a ride. Near the bottom of the ride, there are permanent magnets.
When the copper plate passes the magnets, eddy currents are induced due to magnetic poles in the copper
plate. The eddy currents oppose the direction of the magnet causing the ride to slow down. It slows down
slowly as the eddy currents are proportional to the speed of the plate.
Minimising eddy currents

Eddy currents can be minimised by using a lamented soft iron core. This is made up of thin slices of the iron
separated by an insulating layer of oxide coating or paper. This disrupts the eddy currents and stops them
building up.
9.2 Explain how induction is used in cook tops in electric ranges:
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On each cooking area on the cooktops, there are copper coils wrapped around magnetic materials. An
alternating current is produced and run through the coils producing a magnetic field.
This magnetic field induces an eddy current in the metal pan above.
The resistance in the pan to the current causes heat to be produced at the base of the pan cooking the food.
When more current is run through the coils, there are more eddy currents, making the pan hotter.
Page | 6
An electric generator is one that converts mechanical energy to electrical energy using the principle of electromagnetic
induction.
10.1
Describe the main components of a generator:
Part
Rotor
Armature:
Coil
Brushes
Stator

10.2
Description
Usually consists of several coils wound on an armature which is made to rotate within a
magnetic field.
Cylinder of laminated iron mounted on an axle which is carried in bearings mounted in
the external structure. Torque applied to axle to make the rotor spin.
Each coil consists of many turns of copper wire wound on the armature. The two ends of
each coil are connected either to two slip rings (AC Generator) or two opposite bars of a
split-ring commutator (DC Generator).
The brushes are carbon blocks that maintain contact with the ends of the coils via the
slip rings (AC) or the split-ring commutator (DC), and conduct electric current from the
coils to the external circuit.
Fixed part of the generator which supplies the magnetic field in which the coils rotate.
Magnetic field: The magnetic field
can be provided by permanent
magnets or electromagnets which
are mounted and shaped in such a
way that opposite poles face each
other and wrap around the rotor.
Compare the structure and function of a generator to an electric motor:
Structure:
Similarities:
 Both have a stator providing the magnetic field, both have a rotor which rotates in this field
 In both, the magnetic field is supplied by either permanent magnets or electromagnets
 In both, rotor consists of coils wound on armature connected to brushes.
 In both, their rotor coils are connected to the external circuit through a split ring commutator.
Differences:
 DC Generators and electric motors – use a split-ring commutator to connect external circuit
 AC Generators – use slip rings to connect external circuit
Function:
 The function of an electric motor is the reverse function of a generator
Electric motors:
 Converts electrical energy into mechanical energy
 Rotates when current is supplied
Generators:
 Converts mechanical energy into electrical energy
 Supplies current when rotor rotates
Page | 7
11.1
Describe the differences between AC and DC generators & discuss advantages / disadvantages of AC and DC
generators related to their use:
Description
Advantages
AC generator
 Brushes run on slip rings, constant
connection between coil and external
circuit.
 Induced EMF changes polarity with
every half-turn of the coil
 Voltage in the external circuit varies
like a sine wave
 Current alternates direction
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Disadvantages
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Brushes in AC generator last longer,
increasing efficiency.
Less maintenance and more reliable,
Uses slip rings which cost less to
manufacture and requires less
maintenance
AC voltage can be easily
increased/decreased using
transformers
Can be used for power distribution.
They can be easily designed to
produce 3 phase electricity, meaning
it can be generated over a wide area.
Cannot be used to power some
devices which rely solely on DC
current to function
AC output in different regions around
the country must be synchronised for
correct integration of electricity – i.e.
have the same frequency and are inphase
AC output is much more dangerous
than the equivalent DC output
DC generator
 Brushes run on split-ring commutator,
which work by reversing the connection
between the coil and the external
circuit each half-turn
 Induced emf does not change polarity
 Voltage in external circuit fluctuates
between zero and maximum
 Current flows in one constant direction

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DC output can be used for devices
which rely solely on DC current to
function
DC current is generally more powerful
than AC (for a given voltage)
Its output can be made smoother by
arranging many coils in a regular
pattern around the armature. This
means that the more coils, the more
smoother it is.
Brushes in DC generator do not last as
long because they wear quicker
Chance of creating electrical short
circuit between segments due to pieces
of metal worn from commutator bars
Cannot supply power over long
distance.
The larger the current, the heavier the
rotor coils causing high demands on
structures.
Voltage output
Diagram
Page | 8
Analyse the competition between Westinghouse and Edison to supply electricity to cities:
Westinghouse was the overall winner, as the AC system was more efficient.
Thomas Edison:
 Direct Current System
 DC Generators use commutators, which were a problem – i.e. maintenance, cost, performs poorly at high
speed rotations
 Could only supply power to areas a few kilometres away.
 Relied on thick copper cables to carry electric current
George Westinghouse:
 Alternating Current System
 Westinghouse saw the advantages of AC, and so he purchased the rights to Tesla's AC motors and generators
 AC transmissions through the action of transformers were much more energy efficient.
 Electricity could be transmitted over longer distances with only a small energy loss.
 The motors needed no brushes or commutator.
Identify how transmission lines are insulated from supporting structures and protected from lightning strikes:
Insulation from Supporting Structures:
 Insulation chains- Large insulators that consist of stacks of disks made from porcelain are used to separate
transmission lines from metal support towers. They prevent sparks jumping across the gap between the wires
and towers. The insulators (commonly porcelain) are strong and retains its high insulating properties even
under a very high voltage.
Protection from Lightning Strikes:
 Shield conductors- A non-current carrying wire runs over and parallel to the transmission wires. If lightning
strikes it will hit the overhead wire first and the wire will conduct the huge current of the lightning into the
earth, leaving the transmission wires untouched. The transmission lines do not suffer a sudden surge of
voltage.
 Distance- The distance between towers is at least 150m to protect each tower from other towers if it is hit.
 Earth cable – This runs from the top of the pole down into the earth.
14.1
Discuss the energy losses that occur as energy is fed through transmission lines from the generator to the
consumer:
Energy loss due to resistance:
 As current flows through the transmission lines that has a resistance, heat will be dissipated
 The heat lost during transmission can be quantitatively described by using the formula:
 Formula:
where P = heat lost during transmission (J)
I = the current flow through the wire (A)
2
P=I R
R = the total resistance of the wire (Ω)
(This equation can be derived by combining the power equation P = IV and Ohm’s law V = IR)
Minimisation:
 Transmission at highest possible voltage, lowest possible current
 Careful choice of materials – i.e. using good conductors (e.g. copper), thicker wires = less resistance
Energy loss due to induction of eddy currents:
 Induction of eddy currents in iron core of transformers
 Circulation of eddy currents generates heat representing energy loss to the system
Minimisation:
 Transformer core made of laminated iron - thin layers of iron, separated by thin insulating layers
 Limiting eddy currents and reducing corresponding heat loss by utilising cooling fins on the outside of the
transformer and cooling oil circulating on the inside
Page | 9
Assess the effects of the development of AC generators on society and the environment:

Effects on society:
Positive
Effects:
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Negative
Effects:
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Effects on Environment:
Development of a wide range of
machines, processes and appliances –
improving the standard of living
Many tasks once performed by hand
now can be accomplished with
electrical appliances
Most domestic and industrial work
requires less labour
Influencing technology development tasks such as electronic
communication now achieved
Reduction in demand for unskilled
labour, thus increasing long-term
unemployment
Disruption to supply compromises
safety, causes widespread
inconvenience and loss of production
Injuries and deaths from electric
shocks with the widespread use of AC
power
A major electricity failure could cause
economic crisis
NONE
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Transmission lines criss-cross the
country, strip through
environmentally sensitive areas
Remote wilderness areas tapped
for energy resources such as
hydroelectricity
Air pollution from burning fossil
fuels, cause of acid rain
Global increase of atmospheric
C02, long-term global climate
change
Radioactive waste from nuclear
power stations
Discuss the impact of the development of transformers on society:
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More efficient transmission of electricity – power loss during transmission is dramatically reduced
Allows the development of devices which run at different voltages
Access to high-voltage electricity in remote areas, stepped-down by transformers in order for use in devices
Raised living standards in rural communities (e.g. electrical lighting, refrigeration, air-con.)
Industry no longer clustered around power stations and can be developed away from residential areas
Power stations in remote locations, relocated pollution away from homes
Page | 10
Discuss the need for transformers in the transfer of electrical energy from a power station to its point of use &
explain the role of transformers in electricity sub-stations:

Without transformers electricity would be generated at voltage typically used, resulting in very large energy
losses and costly transmission losses.

In large cities, many power stations would be required every few kilometres and each different voltages
require separate power stations and distribution systems
Transformers:
 More efficient to use very high voltages for long distance transmission
 Transformers step-up voltage for transmission, progressively step-down voltage along transmission lines until it
reaches consumer.
The voltage change during the transmission from the power plant to consumers:
Electricity is usually generated by a three-phase AC generator; generally the voltage generated is as big
as 23000V and current output from each set of the coil is almost 10000A
For long distance transmissions, the electricity is then fed into a step-up transformer that increases the
voltage to 330000V and correspondingly decreases the size of the current (P=VI)
After this electricity has been transmitted over a long distance, the voltage is stepped down at different
regional sub-stations, mainly for safety reasons. Correspondingly, the current increases.
Eventually, the voltage is stepped-down to 240V at the local telegraph pole transformers for domestic
uses; industries may use slightly higher voltages
Describe the purpose of transformers in electric circuits:
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Transformers are devices that increase or decrease the size of the AC voltage as it passes through them via
electromagnetic induction
Step-down transformers are used for appliances containing components requiring lower voltages – e.g. clock
radios, hair dryers, CD players, etc.
Step-up transformers are used for appliances which require higher voltages to function – e.g. televisions, air
conditioners, etc.
Many appliances contain both step-up and step-down transformers supplying different voltages for different
components
Page | 11
Compare step-up and step-down transformers:
Step-up transformer
Step-down transformer

Consists of two inductively coupled coils
wound on a laminated iron core

Consists of two inductively coupled coils wound
on a laminated iron core

More turns in the secondary coil than the
primary coil

Fewer turns in the secondary coil than the primary
coil

Higher output voltage than input voltage

Lower output voltage than input voltage

Lower output current than input current

Higher output current than input current

Used at power stations to increase voltage
and reduce current for long-distance
transmission

Used at substations and in towns to reduce
transmission line voltage for domestic and
industrial use

Used in cathode ray television sets to
increase voltage to operate the picture tube

Used in computers, radios, and CD players to
reduce household electricity to very low voltages
for electronic components
Identify the relationship between the ratio of the number of coils in the primary and secondary coils and the ratio of
primary to secondary voltage:
 Ratio of primary to secondary voltage = ratio of number of turns in the coils
 Step-up transformers - more turns and higher voltage in secondary coil
 Step-down transformers - less turns and lower voltage in secondary coil

where Vp = voltage input into primary coil (V)
Formula:
Vp
Vs
np
ns
Vs = voltage output from secondary coil (V)
np = number of turns of the primary coil
ns = number of turns of the secondary coil
Explain why voltage transformations are related to conservation of energy:
Conservation of Energy:
 Amount of electrical energy entering must equal total energy in all forms leaving
 Power in = power out
 Pp = IpVp = IsVs = Ps
where subscript ‘p’ indicates primary coil and subscript ‘s’ indicates secondary coil
 No power loss – if voltage increases, current correspondingly decreases, and vice versa
Real transformers:
 Heat due to eddy currents acting in the resistance of iron core
 Energy is lost from the system in the form of heat – escaping into the air
 Power output cannot exceed power input, power output is less than power input;
Pinitial > Pfinal
due to loss of heat energy
Page | 12
Discuss why some electrical appliances in the home that are connected to the mains domestic power supply use a
transformer:
Many household appliances function at voltages other than the standard domestic voltage of 240V
Appliances that run on 240V AC:
 Electricity supplied to homes typically 240 V AC
 Many domestic appliances designed to run at this voltage
 Connected directly to the mains supply without a transformer
Running on Lower Voltages:
 Some appliances contain components operating at lower voltages than supplied
 For these appliances, a step-down transformer can be used to decrease the voltage to required – e.g. phone
chargers use a transformer to step-down the voltage from 240V to the required voltage (commonly <10V)
Running on Higher Voltages:
 Appliances such as television receivers and computer monitors contain cathode ray tubes requiring voltages
above supply voltage
 These appliances have a built-in step-up transformer to provide the necessary voltage
Discuss how difficulties of heating caused by eddy currents in transformers may be overcome:
Technique/ part
Laminated iron core
Painting the casing a
dark colour
Internal fan
How it helps
 Stacks of thin iron sheets, each coated with insulation materials.
 Lamination effectively increases the resistance of the core to the flow of eddy
currents, therefore restricting the circulation of large eddy currents – thus, less heat
dissipation
 to absorb the heat produce by the transformer more quickly in order to dissipate it
to the surroundings
 to assist air circulation to remove excess heat faster
filling the
transformer with a
non-conducting oil
Heat-sink fins

which circulates inside the case; transports heat produced in core to outside where
heat can be dissipated to environment

located in wellventilated areas


added to metal transformer case, heat dissipation can occur more quickly over
larger surface area
E.g. up in the air
to maximise air flow around them for cooling
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Describe the main features of an AC electric motor:
Standard AC Electric Motors:
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
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Same features as DC electric motor, except slip rings used instead of split-ring commutator
Slip rings – conducts electricity from the power source without interfering with the rotation of the coil
The motor spins at 50 revolutions per second, as it is the same frequency as the oscillation of AC current (50Hz)
AC Induction Motors:
 Stator:
The stationary component of the motor, it contains the electromagnet coils which create the magnetic field
and it surrounds the rotor.
o Electromagnet coils: When current flows through the coils, it produces a magnetic field. There are 3
pairs of coils in the stator, which when turned on one after the other, creates a rotating magnetic
field.
 Rotor:
The rotating component of the motor. Induced eddy currents flow in the rotor in such a way that it will rotate
in the same direction as the rotating magnetic field created by the stator.
o Squirrel cage: The squirrel cage is made up of parallel aluminium bars that have their ends embedded
in a metal ring at each terminal. It is covered by laminated soft iron and embedded in the stator.
Gather, process and analyse information to identify some of the energy transfers and transformations involving the
conversion of electrical energy into more useful forms in the home and industry
 In the home:
o Ovens and kettles create heat energy from electrical energy
o Stereo systems create sound energy from electrical energy
o Light globes and TVs create light energy from electrical energy
o Washing machines create kinetic energy from electrical energy

In the industry:
o Mainly turning electrical energy into kinetic energy for drills and other machinery
o Light energy in large industrial lights from electrical energy
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