The coil of an electric bulb takes 40 watts to start glowing. If more than 40 W is supplied, 60% of the extra power is converted into light and the remaining int heat. The bulb consumes 100 W at 220 V. Find the percentage drop in the light intensity at a point if the supply voltage changes from `220 V to 200 V`.

Answer

B

Explanation

`P = 100W, V = 220V Case- I : Excess power = 100 -40 = 60W` Power converted to light =` 36 W` Case -II: Power = `82.64 - 40 = 42.64xx60 = 25.584 W p= 36-25.584 = (10,416)/(36) xx100 = 28.93 = 29%`