Question

The variation of potential with distance $R$ from the fixed point is shown in figure.

The electric field at $R=5m$ is

• A. $2.5V{m}^{-1}$
• B. $-2.5V{m}^{-1}$
• C. $0.4V{m}^{-1}$
• D. $-0.4V{m}^{-1}$

Answer 1

The correct option is A

$2.5V{m}^{-1}$

Step 1: Formula for electric field intensity

$E=-\frac{dV}{dR}$,

Here,

$V$ is the potential difference.

$R$ is the distance.

As, we can see from the figure that the slope between distance $4m$ to $6m$ is same, which means the electric field intensity will be the same as well.

Step 2: Calculation for electric field intensity

$$\begin{gathered} E=-\frac{dV}{dR} \\ E=-\frac{V_{R=6}-V_{R=4}}{6-4} \\ E=-\frac{0-5}{2} \\ E=\frac{5}{2} \\ E=2.5V{m}^{-1} \end{gathered}$$

Thus, option A is correct.