A 120V 60W lamp is to be operated on 220V ac su... - JAMB Physics 2007 Question
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
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.
\( \implies R = \frac{V^2}{60} = \frac{120 \times 120}{60} = 240Ω \)
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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