Figure `6.51` shows a simple a potentiometer circuit for measuring a small emf produced by a thermocouple.

The meter wire `PQ` has a resistance of `5 Omega`, and the driver cell has an emf of `2.00 V`. If a balance point is obtained `0.600 m` along `PQ` when measuring an emf of `6.00 mV`,
what is the value of resistance `R`?

Options

A. `995 Omega`
B. `1995 Omega`
C. `2995 Omega`
D. None of these

Answer

A

Explanation

`I =(2/(5 + R))A`
`V(l = 0.600m) =(5/l xx 0.6) xx 2/(5 +R)`
`rArr 6 xx 10^(-3) = 6/(5 + R)`
`rArr 5 + R = 1000 rArr R = 995 Omega`