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Which diagram shows the correct magnetic field pattern around a current-carrying solenoid?
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Which diagram shows the correct magnetic field pattern around a current-carrying solenoid?
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Which diagram correctly shows the magnetic field lines around a current-carrying wire if the current is directed out of the page?
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Which device uses a split ring commutator?
d.c. motor
transformer
relay
a.c. generator
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A simple d.c. electric motor is shown in the diagram.
Which of the following changes would make the coil turn more quickly?
Reducing the strength of the magnetic field.
Reversing the direction of the current and swapping the magnetic poles.
Swapping the magnetic poles.
Increasing the current in the coil
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The number of turns in the primary coil and secondary coil of a transformer is Np and Ns respectively.
Which of the following statements represents a step-up transformer?
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When a wire is moved through a magnetic field, an e.m.f. is induced in the wire.
Which of the following devices uses this effect?
electric motor
electricity generator
photon accelerator
transformer
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Which graph represents the output of a simple a.c. generator?
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Transformers are used to change the voltage of a power supply.
The diagram below shows a simple transformer.
If the input voltage is 48 V, what is the output voltage?
2.4 V
9.6 V
240 V
667 V
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A current-carrying wire is placed between two magnetic poles as shown in the diagram below. It experiences an upwards force.
What is the orientation of the magnetic poles?
Left magnet |
Right magnet |
|
A |
N |
N |
B |
S |
N |
C |
N |
S |
D |
S |
S |
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A transformer is used to raise the voltage of electricity produced at a power station before it is transmitted in power lines.
The power station generates electricity at a voltage of 25 kV and a current of 4000 A. The step-up transformer increases the voltage to 400 kV.
Assume that the transformer is 100% efficient.
What current flows in the power lines?
0.25 A
250 A
640 A
64 000 A
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A transformer has 1200 turns on its secondary coil and has an output voltage of 240 V.
If the input voltage is 12 V, how many turns are there on the primary coil?
2
60
1200
24 000
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A current-carrying wire is placed into a magnetic field as shown in the diagram. The wire experiences a force.
In which direction does the force on the wire act?
OP
PO
ST
QR
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