Practice Questions

1.A transformer has a primary potential difference of 100 V and a primary current of 0.3 A.The secondary potential difference is 20 V.

What is the secondary current, assuming the transformer is 100% efficient?

2.A transformer supplies a secondary coil with a current of 8.0 A at 50 V. The primary coil is supplied with 230 V and carries a current of 2.0 A.

(a) Calculate the input power and output power of the transformer.

(b) Determine the efficiency of the transformer.

(c) Suggest one reason why the efficiency is less than 100%.

3.A phone charger contains a transformer that steps the mains voltage down to 5 V for charging. A current of 0.5A runs from the transformer to the phone.

(a) What is the current supplied by the primary coil if the secondary current is 2.0 A?

(b) Explain why the current is different on each side of the transformer.