NCERT Solution for Class 10 Science Chapter 12
Electricity
NCERT Books for Session 2022-2023
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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Power of first lamp (P1) = 100 W
Potential 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