(1) Joule’s law of heating states that the power of heating obtained by an electrical conductor is directly proportional to the
(a) Product of its resistance and
(b) Square of the electric current passing through the conductor.
(c) Duration for which the conductive current flows.
Following are the two gases that are filled in filament type electric light bulbs:
The filament in an electric bulb is made using tungsten which would burn quickly when it comes in contact with the oxygen in the air. This is the reason why unreactive gases such as argon and nitrogen are used for filling an electric bulb. These gases are chemically interactive.
Power (P) = 840 W
Voltage (V) = 220V
To calculate I =? and R =?
Power input (P) = VI
I = P/V
I = 840/220
I = 3.82 A
The resistance of the electric iron (R) = V/I
R = 220/3.82
R = 57.59 Ω