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The line integral of the electric field along the circumference of a circle of radius r, drawn with a point charge Q at its centre, will be .........

Asked in RS Academy GUJCET booklet · Relation between field and potential

Answer: (3) zero

Step-by-step solution

Idea: the line integral is ∮⃗E· d⃗l taken once around the circle.

The field of the point charge is radial, while along the circle d⃗l is tangential, so the angle between them is 90°.

⃗E· d⃗l = E dl cos 90° = 0 at every point, so the integral is zero.

More generally, the electrostatic field is conservative: ∮⃗E· d⃗l = 0 around any closed path.

So the line integral is zero.

Why the other options are wrong

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