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Amelia Ali

In India electricity supplied for domestic use is 220V, and 110 V in USA. If the resistance of a 60 W bulb for use in India is R, the resistance of a 60 W bulb for use in USA will be 1. R 2. 2 R 3. R/4 4. R/2

Posted in Physics, asked by Amelia Ali, 6 years ago. 4083 hits.
In India electricity supplied for domestic use is 220V, and 110 V in USA. If the resistance of a 60 W bulb for use in India is R, the resistance of a 60 W bulb for use in USA will be 1. R 2. 2 R 3. R/4 4. R/2 - Amelia Ali 6 years ago

9

+5

R/4 is the answer.
Explanation.
The power dissipation of the bulb is written as:
P= V^2 / R 
we have same P for different values of V, so R will also be different for both cases. 
For India:
P = V^2 / R 
it means:
R = V^2/P = 220^2 / 60 = 806.66
now for USA
R = V^2 / R = 110^2 / 60 = 201.667
Comparing these two values we get that R of bulb in USA is 4 times less than those in India. so 3rd option is the correct. 

Hassan Shahbaz
Hassan Shahbaz - 6 years ago
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