Transformers – Practice


1) A transformer at a substation changes 10000 V to 240 V. There are 4000 turns on the primary coil.

a) What type of transformer is this?

b) Calculate how many turns there are on the secondary coil:

2) A television has 5000 turns in the primary coil. The secondary coil consists of 250 turns and draws a current of 8 amps.

a) What is the current that is flowing in the primary coil?

b) What is the power output of the television? (Assume it is an ideal transformer)

3) An ideal transformer has 750 turns on the primary coil and 50 turns on the secondary coil. The current in the secondary coil is 3 A  and the primary voltage is 30 V. Calculate:

a) the secondary voltage

b) the output power

c) the input power

d) the current flowing through the primary coil.

Quick Answers:

1a) step down    b) 96

2a) 0.4A    b) 96W

3a) 2V    b) 6W    c) 6W    d) 0.2A

Worked Answers: