Question

Two lamps, one rated 40 W at 220 V and the other 100 W at 220 V, are connected in parallel to the electric supply at 220V.
(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.

Answer 1

(a)
(b) `{:(P_(1)=40 W", "V_(1)=220V", "I_(1)=?,|,P_(2)=100 W", "V_(2)=220V", "I_(2)=?),(I_(1)=P_(1)/V_(1)=40/220=2/11" ampere",I_(2)=P_(2)/V_(2)=100/220=5/11" ampere",):}`
Total current drawn, `I=I_(1)+I_(2)=2/11+5/11=7/11` ampere
(c) `{:(E_(1)=P_(1)xxt,|,E_(2)=P_(2)xxt),(=40xx1=40 Wh,=100xx1=100 Wh,):}`
Total energy consumed `=40 Wh+100 Wh = 140 Wh =140/1000` kWh `=0.14` kWh