Question

To find the internal resistance of a cell using potentiometer readings

Answer 1

Hey dear,
It's a big experiment. I'll only explain the calculation part.

◆ Potentiometer -
A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider.

◆ Experiment -
[Refer to the diagram for arrangements]

Let l1 be null point obtained when key K1 is closed,
E = Kl1 = (S+r)I ...(1)
V = Kl2 = SI ...(2)

Dividing (1) by (2),
(S+r)/S = l1/l2
r = S(l1-l2)/l2

Therefore, internal resistance of the potentiometer is S(l1-l2)/l2 .

Hope this helps...