Question

A domestic electrical appliance requires alternating current of 15 V. If 220 V of alternating current is supplied to the house, then the device that helps in the functioning of that electrical appliance is

• A. Induction coil
• B. Step-up transformer
• C. AC dynamo
• D. Step-down transformer

Answer 1

The correct option is D Step-down transformer

A step down transformer is one in which the secondary coil has lesser number of turns in secondary coil than in primary coil. Due to this the ratio of voltages in the coils is

$\frac{V_s}{V_p}=\frac{N_s}{N_p}$

Hence the voltage across the secondary coil in the step down transformer is reduced.

Therefore such a transformer is used to apply a voltage of $15V$ across a device when alternating voltage of $220V$ is applied.