Question on: JAMB Physics - 2007
A 120V, 60W lamp is to be operated on 220V ac supply mains. calculate the value of non inductive resistance that would be required to ensure that the lamp is run on correct value
A
100Ω
B
200Ω
C
300Ω
D
500Ω
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Correct Option: B
Power of the lamp = 60W = ( \frac{v^2}{R} ) and the voltage rate = 120V
( \implies R = \frac{V^2}{60} = \frac{120 \times 120}{60} = 240Ω )
Now, if the resistance of the lamp is 240Ω the fuse wire that should ensure current does not exceed this value should be rated 200Ω.
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