The potentiometer wire AB shown in figure is 50 cm long. When AD = 30 cm, no deflection occurs in the galvanometer. Find R.

Concepts/Formula used:

Wheatstone bridge:

The condition for no deflection through the galvanometer is

Here and .

When no deflection occurs,

Let the resistance per cm of the potentiometer wire be be ρ .

Hence, and .

Using the equation when there is no deflection for a Wheatstone bridge/potentiometer, we have