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An electric bulb marked 40 W and 200 V, ...

An electric bulb marked 40 W and 200 V, is used in a circuit of supply voltage 100 V. Its power is

A

100W

B

20W

C

40W

D

10W

Text Solution

Verified by Experts

The correct Answer is:
D
Actual power of bulb `(P_(1))=40 W `
Actual voltage of bulb ` (V_(1))=200V and ` supply voltage ` (V_(2))=100 V ` .
Power `(P)=(V^(2))/(R) prop V^(2) . ` Therefore ` (P_(1))/(P_(2))=(V_(1)^(2))/(V_(2)^(2))` or `, (40)/(P_(2))=((200)^(2))/((100)^(2))=4 or P_(2)=(40)/(4)=10W ` ( where `P_(2)`=power when voltage is 100 V ).
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