Question

Calculate the current through a 60 W lamp rated 250 V. If the line voltage falls to 200 V, how is power consumed by the bulb affected?

Answer 1

Given ,

Power P = 60 W

Voltage , V = 250 V

As Power , P = VI

I = `60/250 = 0.24 "A"`

Resistance of bulb R = `"V"^2/"P" = 250^2/60 = 1041.6  Omega`

Now if voltage falls to 200 V , power consumed will be

P = `"V"^2/"R" = 200^2/1041.6 = 38.4  "W"`