A coil has a resistance of at room temperature

PHYSICS · Single correct · A Level · Physics · Electricity · Electricity

Problem

A coil has a resistance of

20\,\Omega

at room temperature. It is connected to a

100\,\text{V}

supply, and the electrical power developed in the coil is maintained at this value even when its resistance rises to

25\,\Omega

on heating. To keep the power unchanged, the supply voltage should be adjusted to (a)

125\,\text{V}

(b)

89.4\,\text{V}

(c)

112\,\text{V}

(d)

100\,\text{V}