Q. 243.9( 20 Votes )

Two lamps, one rated 40 W at 220 V and the other 60 W and 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.

(b) Calculate the total energy consumed by the two lamps together when they operate for one hour.

Answer :


(b) As the connection is in parallel.

So voltage across both the bulbs is same and is equal to 220V.
Using the Formula P=VI,We can get I as I=P/V Where:-
P= Power
V=Voltage/Potential Difference

Current through AB i.e 40W lamp = I1 = P1/V = 40/220 A

Current through CD i.e. 60W lamp = I2 = P2/V = 60/220 A

Total current drawn from the electric supply = 40/220 + 60/220 = 0.45 A

(c)We know that Energy= Power x Time

Total Power to two bulbs together=40W+60W=100W

According to the question both of the bulbs are being operated together at 1 hour

∴ Energy= 100W x 1hr
   Energy= 100Whr
We know 1Whr= 3600 Joules
∴100Whr= 3600 X 100

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