Question

To compare the emf of two of two given primary cells 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 attached image for arrangement of apparatus].

Let E1 and E2 be emf of two cells.

Firstly we'll close the key a and keep b open, let l1 be null point obtained.
E1 = Kl1

Now, open the key a and close b, let l2 be null point obtained.
E2 = Kl2

To compare emf,
E1 / E2 = (Kl1) / (Kl2)
E1 / E2 = l1 / l2


Hope this helps...