Question

If a bulb of rating 200 V/100W is used at 100V, then what' will be the power of the bulb

Answer 1

Answer: given -

V = 200V

P= 100W

So we know that

P= V^2/R

R= V^2/P

That is 200x200/100

We get 400ohm = RESISTANCE

Voltage is = 100V

P= 100x100/400

P=25W

Hence power is 25W.

Answer 2

Given,

A bulb of rating 200 V/100W is used at 100V.

To find,

The power of the bulb.

Solution,

We can simply solve this numerical problem by using the following process:

Let us assume that the power of the bulb in the later condition is x W.

Mathematically,

Power = (voltage)^2/(resistance)

=> Resistance = (voltage)^2/(power){Statement-1}

According to the question,

Resistance of the bulb in initial condition = resistance of the bulb in later condition

{Since the resistance of the bulb remains unchanged}

=> (initial voltage)^2/(initial power) = (changed voltage)^2/(changed power)

=> (200 V)^2/(100 W) = (100 V)^2/(x W)

=> (4/100 W) × (100 V)^2 = (100 V)^2/(x W)

=> (4/100 W) = 1/(x W)

=> x W = (100/4) W

=> x = 25 W

=> the power of the bulb in the later condition = 25 W

Hence, the power of the bulb in the later condition is equal to 25 W.