Question

Equipotential surfaces are shown in the figure. Find the magnitude and the direction of the resultant electric field.

• A. 200 V/m making an angle ${60}^o$ with the positive x-axis.
• B. 200 V/m making an angle ${120}^o$ with the positive x-axis.
• C. 200 V/m making an angle ${120}^o$ with the negative x-axis.
• D. 100 V/m making an angle ${60}^o$ with the x-axis.

Answer 1

The correct option is B 200 V/m making an angle ${120}^o$ with the positive x-axis.

Since, each of the equipotential surfaces are parallel to each other,
the perpendicular distance between them is given by
d $=10sin30=$ 5
Now, the potential gradient between 2 consecutive planes is 10V
So, the electric field is given by, E $=\frac{V}{d}=\frac{10}{5}\times 100=$ 200
Direction of Electric field is from higher potential surface towards the lower potential surface . Hence , an Obtuse angle .