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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?
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Solution
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"`
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