Question

A bulb is rated $150W$ for $220VAC$ supply of $60Hz$ calculate:

1. Resistance of bulb

2. RMS value of current in bulb

Answer 1

Given that,

Voltage $V=220volt$

Power $P=150W$

Now, the resistance of the bulb is

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

$R=\frac{220\times 220}{150}$

$R=322.67\Omega$

Now, the rms current through the bulb

$P=I_{rms}\times V_{rms}$

$I_{rms}=\frac{P}{V_{rms}}$

$I_{rms}=\frac{150}{220}$

$I_{rms}=0.68A$

Hence, the resistance is $322.67\Omega$ and the rms current is $0.68A$