NCERT Solution for Class 10 Science Chapter 12

Electricity

NCERT Books for Session 2020-2021

CBSE Board and UP Board

Exercises Questions

Page No-222

Questions No-15

# Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V?

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For the lamp one: Power P1 = 100 W and Potential Difference V = 220 V

Therefore,

𝐼1=𝑃1/𝑉=100220=0.455 𝐴

For the lamp two: Power P2 = 60 W and Potential Difference V = 220 V

Therefore,

𝐼2=𝑃2/𝑉=60/220=0.273 𝐴

So, the net current drawn from the supply is given by

𝐼=𝐼1+𝐼2=0.455+0.273=0.728 𝐴

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https://www.tiwariacademy.com/ncert-solutions/class-10/science/chapter-12/

Power of first lamp (P

_{1}) = 100 WPotential difference (V) = 220 V

I=P/V= 100/220A= 0.455A

Resistance of lamp 1= V/I= 220/(100/220)= 484ohm.

Therefore,

𝐼2=𝑃2/𝑉=60/220A=0.273A

So, the net current drawn from the supply is given by

𝐼=𝐼1+𝐼2=0.455+0.273=0.728 𝐴