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Question: Answered & Verified by Expert
When a battery of emf 8 V with internal resistance 0.5 Ω is charged by a 120 V DC supply using a series resistance of 15.5 Ω, then the terminal voltage of the battery is
PhysicsCurrent ElectricityJEE Main
Options:
  • A 11.5 V
     
  • B 20 V
  • C 21.5 V
  • D 12.3 V
Solution:
1439 Upvotes Verified Answer
The correct answer is: 11.5 V
 
Here, emf of the battery =8 V

The internal resistance of the battery, r=0.5 Ω

The voltage of D. C supply = 120 V

External resistance, R=15.5 Ω

When the battery of emf 8 V is charged from a DC supply of 120 V, the effective emf in the circular is

ε=120-8=112 V

The total resistance of the circuit =R+r

  =15.5+0.5 Ω=16 Ω

    Current in the circuit during charging

I=εR+r=11216=7 A

   The terminal voltage of the battery,

V=emf of the battery+voltage drop across the battery

 =8+Ir=8+70.5=11.5 V

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