Electromagnetic Effects (Cambridge O Level Physics)

Which of the following methods could be used to demagnetise a permanent magnet?

After 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?

When 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?

Beta 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?

One of the diagrams below represents the output of a simple A.C. generator.

Which one is correct?

The diagram shows an electromagnet.

How can the strength of the magnetic field around the electromagnet be increased?

A 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?

Which transformer arrangement produces an output e.m.f. that is larger than the input p.d.?

Why is a relay used in a switching circuit?

The 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?

A horizontal beam of electrons passes between the two poles of a magnet in a vacuum.

In which direction is the beam deflected?

The diagram shows a current-carrying conductor between the poles of a magnet. The force on the wire acts downwards. 

Four changes are possible.

1. The current is increased.
2. A stronger magnet is used. 
3. The current is reversed. 
4. The poles exchange positions.

Which two changes made together keep the force acting downwards? 

In 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?

A 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?

Transformers 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?

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?

A 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?

A 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?