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:

In the following set up of potentiometer, the value of potential gradient is:

AP is balancing length for the primary cell of emf E, Resistors of AB length of the wire $P_{AB} = 8 Ω$, and length AB(L) = 10 m.

0.16 volt/m

The correct answer is Option (4) → 0.16 volt/m

Current in the circuit,

$i=\frac{v}{R+r} \Rightarrow i=\frac{2}{2+R_{A B}} \Rightarrow i=\frac{2}{2+8}=\frac{1}{5} A$

Potential gradient = $\frac{i \times R_{A B}}{l}=\frac{1}{5} \times \frac{8}{10}$ = 0.16 volt/m