Question

In India electricity is supplied for domestic use at 220 V. It is supplied at 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(a) R/2(b) R(c) 2R(d) R/4

Answer 1

d is the correct answer

Answer 2

Answer:

D) R/4

Explanation:

Supply in India = 220V (Given)

Supply in USA = 110V(Given)

Power = V²/ Resistance

The power dissipation of the bulb - P= V² / R  

We have same P for different values of V, therefore R will also be different for both cases.  

For India: - P = V² / R, thus

R = V²/P = 220² / 60

= 806.66

For USA  - R = V² / R

= 110² / 60

= 201.667

Comparing the two values, we can see that the R of bulb in USA is 4 times less than those in India. Thus the resistance for use in USA will be = R/4