Question

Two electric bulbs rated 100W 220V and 60W 220 V are connected in parallel in an electric mains of 220V . Find the current drawn by the bulbs from the mains. Cbse science set 3 2019...

Answer 1

for the first lamp, Power= 100W, and rated voltage= 220V

P₁=(V²/R₁)

R₁=(V²/P₁)=(220²/100)=484Ω

For second lamp,  Power= 60W, and rated voltage= 220v

R₂=(V²/P₂)=(220²/60)= 807Ω

So current in first lamp,

I₁=V/R₁= 220V/484Ω=  0.455 Amp

Current in 2nd lamp,

I₂=V²/R₂= (220²V/807Ω)= 0.273 Amp  

Answer 2

Two electric bulbs rated 100W 220V and 60W 220 V are connected in parallel in an electric mains of 220V . Find the current drawn by the bulbs from the mains. Cbse science set 3 2019...

Bulb 1 = 100W , 220V

R1 = V²/P  = 220²/100 = 484 Ω

R2 = 220²/60 = 2420/3 Ω

Connected in Parallel

So net Resustance =  1/ (1/R1 + 1/R2)   =   1/(1/484 + 3/2420)

= 2420/(5 + 3)

=  302.5 Ω

I = V/R

I = 220/302.5

I = 0.727 A