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Question: Answered & Verified by Expert
A potentiometer wire AB having length L and resistance 12r is joined to a cell D of emf ε and internal resistance r. A cell C having EMF ε/2 and internal resistance 3r is connected. The length AJ, at which the galvanometer, as shown in the figure, shows no deflection is

PhysicsExperimental PhysicsJEE MainJEE Main 2019 (10 Jan Shift 1)
Options:
  • A 512L
  • B 1124L
  • C 1112L
  • D 1324L
Solution:
2511 Upvotes Verified Answer
The correct answer is: 1324L
Potential difference across AJ=I RAJ,

=ε13r·12rL·x

For no current in galvanometer,

ε2= potential difference across AJ

ε2=12ε13Lx

x=13L24

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