(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 current drawn by two bulbs from the line, if the supply voltage is 220 V.

(a) Joule's law of heating states that the heat produced in a conductor is directly proportional to the square of the current flowing through it, the resistance of the conductor, and the time for which the current flows. Mathematically, it can be expressed as: H = I^2Rt (b) To find the current drawn by the two bulbs from the line, we need to use the concept of power and resistance. The power of the first bulb is 100 W and the voltage is 220 V, so the current drawn by the first bulb is: I1 = P1/V = 100/220 = 0.45 A The power of the second bulb is 60 W and the voltage is 220 V, so the current drawn by the second bulb is: I2 = P2/V = 60/220 = 0.27 A The total current drawn by the two bulbs from the line is: I = I1 + I2 = 0.45 + 0.27 = 0.72 A