Question

An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be − (a) 100 W (b) 75 W (c) 50 W (d) 25 W

Answer 1

Hey Dear,

◆ Answer - (d)

P = 25 W

● Explaination -

Given are voltage and power rating of the electric bulb.

Resistance of electric bulb is calculated as -

R = Vo²/Po

R = 220²/100

R = 484 ohm

Now power consumed by the bulb at 110 V is given as -

P = V²/R

P = 110²/484

P = 25 W

Therefore, power consumed by the bulb at 110 V is 25 W.

Thanks dear.

Answer 2

Answer:

The consumed power will be equal to 25 W (D)

Explanation:

We know that the formula for power is,

$P = \frac {V^2}{R}$  

Given that,

If V = 220 V we have

$100 W = \frac {220^2}{R}$

$R = \frac {220^2}{100}$

R = 484 Ω.

This is the resistance of the bulb.

When V = 110 V,

Power consumed

$P = \frac {V^2}{R}$  

$= \frac {110^2}{484}\\\\= 25 W.$

Thus, the consumed power will be equal to 25 W