If voltage across a lamp increases by 2%, then the increase in its ...

Question

If voltage across a lamp increases by 2%, then the increase in its power will be

Accepted Answer

Power $P = V^2/R$, so:
$$\frac{\Delta P}{P} = 2 \cdot \frac{\Delta V}{V} = 2 	imes 2\% = 4\%$$