Question

In the figure shown, the electric field intensity at $r=1m$, $r=6m$, $r=9m$ in $V{m}^{-1}$ is :

• A. $-5,-1.67,+5$
• B. $-5,0,+5$
• C. $0,1.67,0$
• D. $+5,1.67,-5$

Answer 1

The correct option is B $-5,0,+5$

We know: $E=\frac{-dV}{dr}$
Given plot shows the variation of $V$ against $r$.
$\therefore \frac{dV}{dr}$ is the slope of graph
Since, slope at $(1,5)$ is $5$, therefore $E{|}_{r=1m}=-5$

Since, slope at $(6,10)$ is $0$, therefore $E{|}_{r=6m}=0$

Since, slope at $(9,5)$ is $-5$, therefore $E{|}_{r=9m}=5$