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Current Electricity

Question
CBSEENPH12039958

A potentiometer wire of length L and a resistance r are connected in series with battery of e.m.f. Eo and a resistance r1. An unknown e.m.f is balanced at a length l of the potentiometer wire. The e.m.f E will be given by

  • fraction numerator LE subscript straight o straight r over denominator Ir subscript 1 end fraction
  • fraction numerator straight E subscript straight o straight r over denominator left parenthesis straight r space plus straight r subscript 1 right parenthesis end fraction. space I over L
  • fraction numerator straight E subscript straight o straight I over denominator straight L end fraction
  • fraction numerator LE subscript straight o straight r over denominator left parenthesis straight r plus straight r subscript 1 right parenthesis straight l end fraction

Solution

B.

fraction numerator straight E subscript straight o straight r over denominator left parenthesis straight r space plus straight r subscript 1 right parenthesis end fraction. space I over L

Consider a potentiometer wire of length L and resistance r are connected in series to a battery of emf Eo and a resistance r1as shown in a  figure.
Current in wire AB = Eo/r1 +r


Potential space gradient comma
straight x space equals Ir over straight L space equals space open square brackets fraction numerator straight E subscript straight o over denominator straight r subscript 1 plus straight r end fraction close square brackets straight r over straight L
emf space produced space across space straight E space will space be space given space by

straight E space equals space straight x. straight l space equals space open square brackets fraction numerator straight E subscript straight o straight r over denominator straight r subscript 1 plus straight r end fraction close square brackets straight I over straight L