Chapter 11

NCERT
Class 10
Science
Solutions
3. An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be : (a) 100 W (b) 75 W (c) 50 W (d) 25 W

Question:

An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be :

(a) 100 W                 (b) 75 W

(c) 50 W                  (d) 25 W

Answer:

(d) 25 W

Explanation: Resistance of bulb

R = V2/P

R = (220 X 220)/100

R = 484Ω

Power used by 110 V bulb

P' = V2/R

    = (110 X 110)/484

   =25W

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