MAGNETISM IGCSE/GCSE

1 A metal bar PQ hangs from a thin thread and always comes to rest with end P pointing north. Another bar XY of the same metal settles in no definite direction.

What happens if the two bars are brought near one another?

• End P and end Q both attract end X.

• End P attracts end X but repels end Y.

• End P neither attracts nor repels end X.

• End P repels end X but attracts end Y.

The diagram shows a 12 V d.c. power supply connected across a coil with a metal core.

The core becomes a magnet when the current is switched on. It remains a magnet after the current is switched off.

From which metal is the core made?

• aluminium

• copper

• soft iron

• steel

What always produces a permanent bar magnet?

• an iron bar in a coil carrying alternating current (a.c.)

• an iron bar in a coil carrying direct current (d.c.)

• a steel bar in a coil carrying alternating current (a.c.)

• a steel bar in a coil carrying direct current (d.c.)

Which material is best for magnetic screening?

• copper

• iron

• lead

• plastic

Which material is used to magnetically screen electrical equipment from unwanted magnetic fields?

• aluminium

• iron

• steel

• copper

Which list contains an example of a non-magnetic material, a magnetic material and a magnetised material?

• copper, iron, a compass needle

• copper, iron, polythene

• iron, steel, a compass needle

• iron, steel, polythene

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

Which row describes the ease with which iron or steel can be magnetised and demagnetised?

• A

• B

• C

• D

The diagram shows how a steel bar can be magnetised.

Which statement describes how the steel bar can be demagnetised?

• Reverse the d.c. supply and gradually decrease the current in the circuit.

• Reverse the d.c. supply and gradually increase the current in the circuit.

• Use an a.c. supply and gradually decrease the current in the circuit.

• Use an a.c. supply and gradually increase the current in the circuit.

The diagram shows a model railway signal.

What does the end P do when the switch is closed?

• It goes down and stays down.

• It goes up and stays up.

• It goes down and then returns to its original position.

• It goes up and then returns to its original position.