Question

An electric bulb is rated 100 W, 220 V. What is the resistance of the filament?

Hint:

Use \( P = \frac{V^2}{R} \) when voltage and power are given. Always ensure units are in standard SI form.

Answer 1

Step 1: Use the power-voltage-resistance relation.
The power consumed by a resistive device is given by:
\[ P = \frac{V^2}{R} \] Rearranging to solve for \( R \): \[ R = \frac{V^2}{P} \] Step 2: Substitute the given values.
\[ R = \frac{(220)^2}{100} = \frac{48400}{100} = 484 \, \Omega \]