Answer to Question #92218 in Electrical Engineering for Anurag

Question

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

Answer 1

Length of potentiometer wire=100cm

Total resistance of wire(r)=10

Resistance of 40 cm wire(r₁)=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.