Electromagnetic Effects (Cambridge (CIE) IGCSE Physics): Exam Questions

After electricity is generated at a power station, the voltage is increased significantly for transmission across the country via the national grid.

What is the advantage of transmitting electricity at very high voltages?

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?

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Beta and gamma radiation are passed through two metal plates, with equal and opposite charges, as shown in the diagram below.

Which direction, if any, would the β-particles and γ-rays be deflected?

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Which graph represents the output of a simple a.c. generator?

A simple electric generator induces an electromotive force (e.m.f.).

 Which modification would increase the induced e.m.f.?

An electron moves into a uniform magnetic field.

The arrow shows the initial direction of motion of the electron.

The direction of the magnetic field is into the plane of the page.

In which direction does a force act on the electron when it enters the magnetic field?

Which statement about a transformer is correct?

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?

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A magnetic field can be represented by the diagram shown below. The dots represent magnetic field lines coming out of the page.

A beam of alpha particles is directed through the field as shown above. Alpha particles, being charged, will be deflected by the field.

In which direction will the alpha particles be deflected?

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The south pole of a magnet is brought near to a solenoid, which is connected to an ammeter. The magnet is then pulled away again.

As the magnet is moved towards point P the needle on the ammeter deflects. When it is moved away from point P, the needle on the ammeter also deflects.

What magnetic pole is produced at P when the south pole of the magnet is brought towards and away from the solenoid?

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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?

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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?

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?

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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?

The diagram shows a vertical wire carrying a current I placed between the poles of a magnet.

What is the direction of the force on the wire exerted by the magnetic field?

The diagram shows an a.c. generator.

The graph shows the potential difference (p.d.) between points X and Y plotted against time. A positive value of p.d. indicates that X is more positive than Y.

Which diagram shows the position of the coil at point P on the graph?