(A) (i) Define electric power. Express it in terms of potential difference (V) and resistance (R). (ii) An…
(A) (i) Define electric power. Express it in terms of potential difference (V) and resistance (R).
(ii) An electric oven is designed to work on the mains voltage of 220 V. This oven consumes 11 units of electrical energy in 5 hours. Calculate :
(a) power rating of the oven
(b) current drawn by the oven
(c) resistance of the oven when it is red hot
Solution
(A)
(i) Electric power: Rate at which electrical energy is dissipated or consumed / Rate of supplying energy to maintain the flow of current through a circuit.
P = V2/R
(ii) (a) (1 unit = 1kWh)
Power, P = Electrical energy consumed / Time
= 11kWh/5h = 2.2kW or 2200 W
(b) I = P/V = 2200/220 = 10A
(c) R = V2/P = (220)2/2200 = 22 Ω
(Alternate formula can be used)