Question

An incandescent lightbulb is rated at 120 Watts when plugged into a 200 V-rms household outlet. Calculate the resistance of the filament and the rms current. g

Answer 1

Answer:

• The resistance of the filament is 333.33 ohms

• The rms current is 0.6 A

Explanation:

Given;

output power of the incandescent lightbulb , P = 120 W

input voltage, V = 200 V

The resistance of the filament is calculated as;

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

Where;

R is the resistance of the filament

$R = \frac{V^2}{P} \\\\R = \frac{200^2}{120} \\\\R = 333.33 \ ohms$

The rms current is given as;

$P = I_{rms} V_{rms}\\\\I_{rms} = \frac{P}{V_{rms}} \\\\I_{rms} =\frac{120}{200}\\\\ I_{rms} = 0.6 \ A$