Two lamps, one rated 40 W at 220 V and the other 60 W at 220 V, are connected in parallel to the electric supply at 220 V.
(a) Draw a circuit diagram to show the connections.
(b) Calculate the current drawn from the electric supply.
(c) Calculate the total energy consumed by the two lamps together when they operate for one hour.
Given, 2 lamps: P1 = 40W, P2 = 60W
V = 220V
(a) figure.png
(b) Voltage across both the bulb is same and is equal to 220V.
Current through 40W lamp = I1 = \(\frac{P_1}{V}\)
= \(\frac{40}{220}\)A
Current through 60W lamp = I2 =\(\frac{P_2}{V}\)
= \(\frac{60}{220}\)A
Total current drawn from the electric supply
= \(\frac{40}{220}\)A + \(\frac{40}{220}\)A
= 0.45A
(c) Energy consumed by 40W lamp in 1 hr, E1 = P1 x t
= 40 x 1 = 40Wh
1Wh = 3.6kJ
E1 = 40 x 3.6 = 144kJ
Energy consumed by 60W lamp in 1 hr, E2 = P2 x t
= 60 x 1 = 60Wh = 216kJ
Total energy consumed = 144 + 216 = 360kJ