Question

A potentiometer wire $PQ$ of $1m$ length is connected to a standard cell $E_1$. Another cell $E_2$ of emf $1.02V$ is connected with a resistance $‘r’$ and switch $S$ (as shown in figure). With switch $S$ open, the null position is obtained at a distance of $49cm$ from $Q$. The potential gradient in the potentiometer wire is:

• A. $0.03V/cm$
• B. $0.02V/cm$
• C. $0.04V/cm$
• D. $0.01V/cm$

Answer 1

The correct option is B

$0.02V/cm$

Step 1: Given data

$\begin{array}{rcl}PQ& =& 1m\\ QJ& =& 49cm\\ PJ& =& 51cm\\ E_2& =& 1.02V\end{array}$

Step 2: Find potential gradient

Potential gradient is given by,

$Potentialgradient=\frac{Potentialdrop}{length}$

$$\begin{gathered} =\frac{1.02}{51} \\ =0.02v/cm \end{gathered}$$

Hence, option (B) is correct.