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

Explanation

`P=(V^(2))/(R)` or `R=(V^(2))/(P)`
For heter, Resistane `R_(h)=((220)^(2))/(500)=96.8Omega` For bulb resistance `R_(1)=((220)^(2))/(100)=484Omega`
Current in the circuit when both are connected in series `I=(V)/(R_(L)+R_(h))=(220)/(484+96.8)=0.38A`
(i) power consumed by heater `=I^(2)P_(h)=(0.38)^(2)xx96.8=13.98W`
(ii) Power consumed by bulb `=I^(2)R_(L)=(0.38)^(2)xx484= 69.89W`