Question

a lamp rated 100W at 220V is connected to the main electric supply.

what amount of current is drawn from the supply line if the voltage is 220V

what is its resistance

Answer 1

1 amp, 220²/100=484ohm

Answer 2

When a lamp rated 100 W at 220 V is connected to the main electric supply 0.455 ampere current and 483.5 ohms resistance must be there.  

Given:

P  =  100 W

V  =  220 V

Solution:

Since

P = V × I    

Plug the values in the given formula:

100 W = 220 V × I

$I=\frac{100 \ W}{220 \ V}$

I  =  0.455 amp

Ohm’s law:

V = I × R

220 V = 0.455 × R  

R  = 483.5 ohm