Question

A bulb is marked $220\text{V},100\text{W}$. What will be the current in the filament, when connected to $200\text{V}$ source?

• A. $\frac{30}{121}\text{A}$
• B. $\frac{40}{121}\text{A}$
• C. $\frac{50}{121}\text{A}$
• D. $\frac{60}{121}\text{A}$

Answer 1

The correct option is C $\frac{50}{121}\text{A}$

Resistance of the given bulb can be calculated as,

$R=\frac{V^2}{P}=\frac{{220}^2}{100}=484\Omega$

Thus, current through the bulb, when it is connected across a $200\text{V}$ supply is,

$I=\frac{V}{R}=\frac{200}{484}=\frac{50}{121}\text{A}$

Hence, option $\left(C\right)$ is the correct answer.