Question

A bulb is rated at 220 V, 200 W. What is its resistance?

Answer 1

Step 1: Power:

The power is defined as the work done in per unit time.

The following are given by the question:

The rated voltage of bulb,$V=220\text{V}$

The rated power of bulb,$P=200\text{W}$

The relationship between power, voltage, and resistance is given by

$P=\frac{V^2}{R}$

Step 2:

Derive the expression for the resistance,

$R=\frac{V^2}{P}$

Substitute the values

$$\begin{gathered} R=\frac{{220}^2}{200} \\ R=\frac{48400}{200} \\ R=\frac{484}{2} \\ R=242\Omega \end{gathered}$$

Hence, the resistance of the bulb is $242\text{Ω}$.