Question

A potentiometer wire has a length of 4 m and resistance of 20 Ω. It is connected in series with resistance of 2980 Ω and a cell of emf 4 V. Calculate the potential along the wire.

Answer 1

Length of the potential wire, l = 4 m 

Resistance of the wire, r = 20 Ω 

Resistance connected series with potentiometer wire, R = 2980 Ω 

Emf of the cell, ξ = 4 V 

Effective resistance, R_s = r + R = 20 + 2980 = 3000 Ω

Current flowing through the wire, I = \(\frac{ξ}{r+R_S}\) = \(\frac{4}{3000}\)

I = 1.33 x 10^-3 A

Potential drop across the wire, V = Ir

= 1.33 x 10^-3 3 x 20 V 

= 26.6 x 10^-3 V

= 6.65 x 10^-3 

Potential garadient = 0.66 x 10^-2 Vm^-1