Question

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An electric bulb is rated 220 volt and 100watt, when it is operated at 110v , what will be the power consumed?

Answer 1

The voltage V is related to power P by the formula,

P = I * V

I is the current through the resistance where the voltage is applied. Again,

V=IR.

So, P= V2 / R

Or,  R= V2/P 

Here, R = 2202 /100 = 484 ohms.

Putting this back in the eqn P= V2 / R, with V=  110, 

P= 1102/ 484 = 25 watts. 
Hope this helped mate
 

Answer 2

Answer:

Given

An electric bulb is rated 220V and 100W

Find out

Power consumed when it is operated on 110 V

Solution

As per the equation P = V2/R

we have If V = 220 V

100 W = 2202/R

R = 2202/100 Ω = 484 Ω. This is the resistance of the bulb.

When V = 110 V, power consumed = V2/R = 1102/484 = 25 W.

So, 25 W power is consumed when it is operated on 110 V.