IGCSE TRANSFORMER 2

A step-down transformer is used to light a 12 V lamp from a 240 V mains supply. The lamp lights

at normal brightness. The primary coil has 600 turns.

How many turns are in the secondary coil?

• 12

• 20

• 30

• 50

A steel magnet is placed inside a coil of wire. There is a large alternating current in the coil. The

magnet is slowly moved out of the coil to position P.

How has the steel changed, if at all, when it reaches position P?

• It has become a stronger magnet.

• It has become demagnetised.

• The poles have changed ends.

• There has been no change.

An electric current is passed through a coil of wire.

• A

• B

• C

• D

When a wire is moved upwards between the poles of a magnet, an electromotive force (e.m.f.) is

induced across the ends of the wire.

• cathode-ray tube

• a generator

• a transformer

• an electromagnet

An input voltage of 10 V is supplied to the primary coil of a transformer. An output voltage of 40 V

is produced across the secondary coil.

The 10 V supply at the primary coil is now replaced with a 40 V supply.

What is the new output voltage across the secondary coil?

• 10 V

• 40 V

• 70 V

• 160 V

A metal wire is placed between the poles of a magnet.

The wire can be moved in each of three directions OP, QR and ST.

• OP only

• OP or ST

• QR

• ST only

A transformer has 100 turns on its primary coil and 25 turns on its secondary coil. The primary

coil is connected to a 12 V a.c. supply.

• 3.0 V

• 4.0 V

• 48 V

• 300 V

An input voltage of 10 V is supplied to the primary coil of a transformer. An output voltage of 40 V

is produced across the secondary coil.

The 10 V supply at the primary coil is now replaced with a 40 V supply.

What is the new output voltage across the secondary coil?

• 10 V

• 40 V

• 70 V

• 160 V

The diagram shows cables used in the transmission of electrical energy. High voltages are used

for the transmission.

• Fear of high voltages stops people from interfering with the cables.

• Heat loss in the cables is smaller than if low voltages are used.

• High voltages increase the current in the cables.

• High voltages produce large magnetic fields, so less insulation is needed.

Which diagram shows the magnetic field pattern around a wire that is carrying a current

perpendicular to the page?

• A

• B

• C

• D