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

1. Draw a circuit diagram to show the connections.
2. Calculate the current drawn from the electric supply.
3. Calculate the total energy consumed by the two lamps together when they operate for one hour.

Given,

Power of 1st lamp, P₁ =  40W, Voltage of 1st lamp,  V₁ = 220V

Power of 2nd lamp, P₂ =  60W, Voltage of 2nd lamp,  V₂ = 220V

(a) Circuit diagram of the connections.

We know that, 

$P=V\times I$, where P = Power,  V = Voltage, I = Current.

In term of Current I, it can be given as-

$I=\frac{P}{V}$

Now,

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 = $\frac{40}{220}+\frac{60}{220}=0.45A$

(c) Energy consumed by 40W lamp in 1hr, ${E}_{1}={P}_{1}\times t=40\times 1=40Wh$

So, energy consumed by Lamp-1 = $40\times 3.6=144kJ$  $[\because 1Wh=3.6kJ]$    

Energy consumed by 60W lamp in 1hr, ${E}_{2}={P}_{2}\times t=60\times 1=60Wh$

So, energy consumed by Lamp-2 = $60\times 3.6=216kJ$   $[\because 1Wh=3.6kJ]$    

Total energy consumed = (Energy consumed by Lamp-1 +  Energy consumed by Lamp-2) = 144 + 216 = 360kJ

Hence, the total energy consumed by the two lamps together when they operate for one hour is 360kJ.