Question

If current in an electric bulb is decreased by 25%,
then how will power in the bulb change?
(1) 50%
(2) 56.25%
(3) 36%
(4) 43.75%​

Answer 1

Answer:50%

Explanation:

Answer 2

Power in the bulb changes as :

Let us assume initial current be i.

Given : initial current decreases by 25% i.e it becomes i/4

New current = i - 0.25i = 0.75i

We know that power is given by formula,

$p ={i}^{2}r$

Power is directly proportional to the square of current.

Hence new power = (0.75i)^2×r = 0.5625i^2r

Power change = i^2r - 0.5625i^2r = 0.4375i^2r

Percentage change in power,

= 0.4375i^2r×100

= 43.75% of i^2r