Question

A potentiometer wire has length 2 m and resistance 10 Ω. It is connected in series with a resistance 990 Ω and a cell of emf 2 V. Calculate the potential gradient along the wire.

Answer 1

Data : L 10 m, 

R = 10 Ω, 

R_ex = 990 Ω, 

E = 2 V 

The current in the circuit is

I = \(\cfrac{E}{R+R_{ext}}\) = \(\cfrac2{10+990}\) = \(\cfrac2{1000}\)

= 2 x 10^-3 A

The potential difference across the wire is 

V = IR = 2 × 10^-3 × 10 = 2 × 10^-2 V 

∴ The potential gradient along the wire

 = \(\cfrac V{L}\) = \(\cfrac{2\times10^{-2}}2\) = 10^-2 V/m