(a) Write Joule’s law of heating.
(b) Two lamps one rated 100 W 220 V, and the other 60 W 220 V, are connected in parallel to electric mains supply. Find the currents drawn by two bulbs from the line, if the supply voltage is 220 V.
Joule’s law of heating states that the heat produced in a conductor is directly proportional to
(i) the square of the current I through it,
(ii) its resistance R and
(iii) the time t , for which current is passed.
Therefore, the mathematical expression of Joule’s law of heating is:
H = I 2 Rt
- H = Produced Heat
- I = Current flowing through the device
- t = Time of current flow
- R = Resistance of the appliance