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(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.
Answer:
(a)
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
Where,
- H = Produced Heat
- I = Current flowing through the device
- t = Time of current flow
- R = Resistance of the appliance
(b)
