Mangal's room heater is marked as 1,000 W -200 V. Find the percentage change in the power of the heater, if the voltage drops to 160 V.

A light bulb is rated 50 W for a 220 V supply. Find peak voltage of the source

Find the rate of change of the volume V of a sphere of radius r w.r.t change in the radius.

A parallel plate capacitor is filled by a dielectric whose relative permittivity varies with the applied voltage (V) as epsilon = alpha V where alpha = 2V^-1 . A similar capacitor with no dielectric is charged to V_0 = 78 V . It is then concentrated to the uncharged capacitor with the dielectric. Find the final voltage on the capacitors.