Question #92218

A potentiometer wire of length 100cm has a resistance of 10Ω. It is connected in series to to a

resistance R and a cell of emf 2V and negligible internal resistance. A source of emf of 10mV is

balanced by a length of 40cm of the potentiometer wire. What is the value of the resistance R?

A.526.67 ohm

B.70 ohm

C.1580 ohm

D.zero ohm

resistance R and a cell of emf 2V and negligible internal resistance. A source of emf of 10mV is

balanced by a length of 40cm of the potentiometer wire. What is the value of the resistance R?

A.526.67 ohm

B.70 ohm

C.1580 ohm

D.zero ohm

Expert's answer

Length of potentiometer wire=100cm

Total resistance of wire(r)=10

Resistance of 40 cm wire(r_{1})=4Ω

EMF of driver cell(E)=

External resistance of circuit(R)=R

Current(I) in the circuit is given by = A

Voltage drop across 40 cm potentiometer wire= =

=

This voltage drop is equal to the balancing EMF of or or

so,

It is the right answer.

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