An electric bulb and electric heater are rated `100 W,220 V and 500 W, 220 V` respectively. Both are connected in series to a `220V` d.c. mains. Calculate the power consumed by (i) electric bulb and (ii) heater

Answer

(i)`69.89 W, 13.8 W`

Explanation

Resistance of bulb `R_(1) ((220)^(2))/(100) = 484 Omega`
resistance of heater `R_(2) ((220)^(2))/(500) = (484)/(5) = 96.6 Omega`
Total resistance of series combination
`R = R_(1) + R_(2) = 484 + 96.6 = 580.8 Omega `
current `I = (V)/(R ) = (220)/(5808) = 0.38 A`
(i)power connected by bulb `= l^(2)R_(1)`
`= (0.38)^(2) xx 484= 69.89 W`
(ii) power connected by heater `= l^(2)R_(1)`
`= (0.38)^(2) xx 96.8 = 13.8 W`