1
1 mark
1 markFour students, of varying ability in physics, draw what they believe to be the field pattern of a current-carrying solenoid.
Which of them is correct?
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Electromagnetic Effects (Cambridge O Level Physics)
Topic Questions
21 mark
1 markFour students are asked to draw the magnetic field pattern of a current-carrying wire. The wire is carrying the current out of the page.
The diagrams they draw are shown below.
Which is correct?
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31 mark
1 markWhich device uses a split ring commutator?
A DC motor
A transformer
A relay
An AC generator
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41 mark
1 markA simple DC 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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51 mark
1 markThe 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?
Np = Ns
Np < Ns
Ns < Np
Np > Ns
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11 mark
1 markTransformers are used to change the voltage of a power supply.
The diagram below shows a simple transformer.
If the input voltage is 48V, what is the output voltage?
667V
2.4V
9.6V
240V
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21 mark
1 markA 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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31 mark
1 markA transformer has 1200 turns on its secondary coil, and outputs 240 V.
If the input voltage is 12 V, how many turns are there on the primary coil?
2.4
24,000
60
1200
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41 mark
1 markA current-carrying wire is placed into a magnetic field as shown in the diagram. The wire experiences a force.
In which direction is the force?
OP
PO
ST
QR
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11 mark
1 markWhich of the following methods could be used to demagnetise a permanent magnet?
Cool it to a very low temperature.
Put it in a coil of wire and pass direct current through the wire.
Stroke it in a single direction with a permanent magnet.
Heat it to a high temperature
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21 mark
1 markAfter being produced at a power station, electrical voltage is increased significantly for transportation across the country via the national grid.
What is the advantage of transmitting electricity at very high voltages?
It makes the electricity flow more quickly.
It increases the efficiency of the electricity transfer.
It produces more power.
It is safer to transmit electricity at high voltage.
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31 mark
1 markWhen a wire is moved through a magnetic field, an e.m.f. is induced in that wire.
This rather remarkable effect allows which device to operate?
An electric motor
An electrical generator
A photon accelerator
A transformer.
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41 mark
1 markBeta and gamma radiation are passed through two charged metal plates as shown in the diagram below.
Which direction, if any, would the β-particles and γ-rays be deflected?
| β-particles | γ-rays | |
| A | into the page | continue straight |
| B | towards the negative plate | out of the page |
| C | continue straight | towards the negative plate |
| D | towards the positive plate | continue straight |
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51 mark
1 markOne of the diagrams below represents the output of a simple A.C. generator.
Which one is correct?
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61 mark
1 markThe diagram shows an electromagnet.
How can the strength of the magnetic field around the electromagnet be increased?
Remove the metal core and decrease the current in the circuit
Remove the metal core and keep the current in the circuit constant
Reverse the d.c. supply and decrease the current in the circuit
Reverse the d.c. supply and increase the current in the circuit
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71 mark
1 markA magnet oscillates vertically above a coil of wire.
As the lower end of the magnet oscillates between P and R, a varying e.m.f. is induced across the coil.
When this e.m.f. is 0 V, where could the lower end of the magnet be?
at R only
at Q only
at P or at R
at P or at Q
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81 mark
1 markWhich transformer arrangement produces an output e.m.f. that is larger than the input p.d.?
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91 mark
1 markWhy is a relay used in a switching circuit?
to switch on a small current using a small current
to switch on a small current using a large current
to switch on a large current using a small current
to switch on a large current using a large current
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101 mark
1 markThe diagram shows a horizontal rectangular wire coil WXYZ between the poles of a magnet.
There is a current in the coil in the direction shown.
Which statement is correct?
The side WX experiences an upward force.
The side XY experiences an outward force.
The side YZ experiences an inward force.
The side ZW experiences a downward force.
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111 mark
1 markA horizontal beam of electrons passes between the two poles of a magnet in a vacuum.
In which direction is the beam deflected?
into the page
out of the page
towards the north pole
towards the south pole
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121 mark
1 markThe diagram shows a current-carrying conductor between the poles of a magnet. The force on the wire acts downwards.
Four changes are possible.
- The current is increased.
- A stronger magnet is used.
- The current is reversed.
- The poles exchange positions.
Which two changes made together keep the force acting downwards?
1 and 3
2 and 3
2 and 4
3 and 4
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131 mark
1 markIn an alternating current (a.c.) generator, a magnet rotates near a coil of wire. The induced electromotive force (e.m.f.) in the coil is displayed on an oscilloscope screen.
Which trace is produced as the magnet slows down?
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141 mark
1 markA student uses a transformer to light a filament lamp using a 230 V a.c. supply. The lamp has a maximum voltage rating of 6.0 V
What happens when the circuit is switched on?
The lamp does not light at all.
The lamp lights at normal brightness.
The lamp lights at normal brightness.
The lamp lights up brightly and then goes out.
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