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NCERT Class XII Chapter
Current Electricity
Questions With Solutions

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Question : 4
Total: 24
(a) Three resistors 2 Ω, 4 Ω and 5 Ω are combined in parallel. What is the total resistance of the combination?
(b) If the combination is connected to a battery of emf 20 V and negligible internal resistance. Determine the current through each resistor, and the total current drawn from the battery.
Solution:  

(a) Total resistance of the combination in parallel
1
Req
 =
1
R1
+
1
R2
+
1
R3
 or
1
Req
 =
1
2
+
1
4
+
1
5
 or Req =
20
19
 = 1.05 Ω
(b) Potential of 20 V will be same across each resistor, so current
I1 =
V
R1
 =
20
2
 = 10 A
I2 =
V
R2
 =
20
4
 = 5 A
I3 =
V
R3
 =
20
5
 = 4 A
Total current drawn from the cell,
I = I1+I2+I3 or I = 19 A
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