What is meant by equipotential surface? Show that the amount of work done in moving a test positive charge along the equipotential surface is zero.

Explanation

An equipotential surface is that at every point of which the electric potential is same i.e., there is no difference of potential between any two points on it.
Since potential difference `dV=(dW)/(q)`
In an equipotential surface, `dV=0`
`therefore (dW)/(q)=0`
or `dW=0`
i.e. no work is done in moving a test charge along the equipotential surface.