Question

If 100V is applied across a 200V,100W bulb,the power consumed will be
a)100W b)50W c)25W d)12.5W​

Answer 1

Answer:

C is the right answer

Explanation:

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Answer 2

The required power that the bulb consumes is 25W, and option C (25W) is the correct answer.

Given :

100v is applied across a 200V,100W bulb.

To Find :

the power that the bulb consumes in a 100V application

Solution :

We can find the solution to this problem in the following way.

We know that the power that an electrical item (like a bulb) consumes has the following formula.

$Power=\frac{Voltage^{2} }{Resistance}$

We get that since the resistance of the bulb is constant, we can deduce the following.

$Power\alpha Voltage^{2}$

Let us assume the rated parameters have the suffix 1 and the applied parameters have the suffix 2, as shown below.

$P_1=100W,\\V_1=200V\\V_2=100V\\P_2=?$

We can write the following equation.

$\frac{P_1}{P_2} =(\frac{V_1}{V_2} )^{2} \\\frac{100}{P_2} =(\frac{200}{100} )^{2} \\\frac{100}{P_2} =4\\P_2=\frac{100}{4} \\P_2=25W$

Therefore, the required power that the bulb consumes on the application of 100V is 25W, and option C (25W) is the correct answer.

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