The diagram shows a flat, rectangular coil placed between the poles of a magnet.
There is a current in the coil that makes it turn in the direction shown in the diagram.

Which change would make the coil turn in the opposite direction?

A transformer has 1000 turns on its primary coil. An input voltage of 12 V is applied to the primary coil, and an output voltage of 120 V is induced across the secondary coil.

How many turns are on the secondary coil of the transformer?

A transformer has 400 turns on its secondary coil. An input voltage of 12 V is applied to the primary coil, and an output voltage of 120 V is induced across the secondary coil.

How many turns are on the primary coil of the transformer?

A current-carrying wire XY lies in the magnetic field between the two poles of a U-shaped electromagnet. A force acts on the wire XY because of the magnetic field.

Each of the following actions is carried out separately.

● The current in the wire XY is reversed.
● The magnetic field is reversed.
● Both the current in the wire XY and the magnetic field are reversed at the same
time.

How many of these actions cause the direction of the force on the wire XY to be reversed?

A transformer has 2400 turns on its primary coil and 200 turns on its secondary coil.

What input voltage is needed to give an output voltage of 240 V?

A student investigates electromagnetic induction. She has a bar magnet and a coil of wire that is connected to a sensitive ammeter.

Which movement does not cause a reading on the ammeter?

The primary coil of a transformer has 200 turns. This primary coil is connected to an a.c. power supply of 25 V.
A voltmeter connected across the secondary coil reads 50 V.

How many turns are on the secondary coil?