The resistance of the hot filament of the bulb is about 10 times the cold resistance of a 100 W – 220 V lamp, when not in use, the resistance is

The resistance of the hot filament of the bulb is about

10

times the cold resistance of a

100 W – 220 V

lamp, when not in use, the resistance is

484 Ω

.
It is given that the lamp has the power of

100 W

and the voltage is

220 V

.
From the formula of power, the resistance is given by,

R = \frac{V²}{P}

where

R

is the resistance,

V

is the voltage and

P

is the power.
The lamp has 100 W power and is of 220 V volts.

R = \frac{V²}{P}

R = \frac{220 ²}{100}

R = 484 Ω

Therefore, the resistance of the lamp is

484 Ω

when it is not used.

The resistance of the hot filament of the bulb is about $10$ times the cold resistance of a $100 W – 220 V$ lamp, when not in use, the resistance is