Question

A light bulb is rated 100w for 220v ac supply of 50 hz.Calculate resistance of the bulb

Answer 1

P=100w and V=220v
I = P/V = 100/220=5/11=0.45A
So,R= V/I= 220×11/5=44×11=484 ohm

Answer 2

The resistance of the bulb is 484 ohms.

Explanation:

Given that,

Power of the bulb, P = 100 W

Voltage, V = 220 V

Frequency, f = 50 Hz

To find,

The resistance of the bulb.

Solution,

The power of an electrical device is given by :

$P=V\times I$

Since, V = IR

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

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

$R=\dfrac{(220)^2}{100}$

R = 484 ohms

So, the resistance of the bulb is 484 ohms.

Learn more,

Power of an electrical device

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