Magnetic Fields

Which properties make materials suitable for use as a core in an electromagnet?

• difficult to magnetise and easy to demagnetise

• difficult to magnetise and retains magnetic strength

• easy to magnetise and retains magnetic strength

• easy to magnetise and easy to demagnetise

The coil in an electric motor is wound onto a cylinder.

Why is the cylinder made of soft iron?

• to deflect the magnetic field away from the coil

• to increase the current through the coil

• to increase the strength of the magnetic field through the coil

• to support the coil and prevent it from collapsing

A student investigates which end of a magnetic compass needle is attracted to a bar magnet.

What does the investigation show?

• Both ends of the compass needle are attracted by the north pole of the magnet.

• Both ends of the compass needle are attracted by the south pole of the magnet.

• One end of the compass needle is attracted by the north pole and the other end by the south pole.

• The compass needle is not attracted by either end of the magnet.

The diagram shows some nails attracted to a metal rod by magnetic induction.

From what could the metal rod be made?

• aluminium

• copper

• iron

• magnesium

A small compass is placed close to a strong bar magnet, the same distance from each end.

Which diagram shows the direction in which the compass needle points?

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Which diagram shows the magnetic field around a bar magnet?

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An electromagnet is used to separate magnetic metals from non-magnetic metals.

Why is steel unsuitable as the core of the electromagnet?

• It has a high thermal capacity.

• It has a high density.

• It forms a permanent magnet.

• It is a good conductor of electricity.

Which of the following best illustrates the magnetic field around a wire that carries an electric current out of the paper?

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