Potentiometer has multiple uses. It is based on the principle that when constant current flows through a wire of uniform area of cross-section then potential drop along its length is directly proportional to corresponding length.

i.e.  $V \propto I$

$V=K I$

Various uses of potentiometer on:

• To measure potential differences between any two points in an electrical network
• To compare emf of a cell
• To measure emf of a cell
• To measure internal resistance of a cell etc.

Answer the following question related to potentiometer:

What happens to the balancing length when resistance S is increased?

Balancing length increases

The correct answer is Option (2) → Balancing length increases

Terminal potential difference across battery, = $E – ir$

⇒  $E-\frac{E}{S+r} . r$

Now as the value of S is increased, terminal potential difference increases hence balancing length increases.