If a unit positive charge is taken from one point to another over an equipotential surface ,then

Options

A. work is done one the charge
B. work is doen by the charge
C. work done is constant
D. no work is done

Explanation

To solve the problem, we need to understand the concept of an equipotential surface and the work done when moving a charge on such a surface.

### Step-by-Step Solution:

1. **Understanding Equipotential Surfaces**:
An equipotential surface is a surface on which the potential is the same at every point. This means that if a charge is moved along this surface, there is no change in electric potential energy.

2. **Work Done on Equipotential Surfaces**:
The work done \( W \) in moving a charge \( q \) from one point to another in an electric field is given by the equation:
\[ W = q \cdot (V_f - V_i) \]
where \( V_f \) is the final potential and \( V_i \) is the initial potential.

3. **Applying the Concept to a Unit Positive Charge**:
In this case, we are moving a unit positive charge (\( q = 1 \, C \)) from one point to another on an equipotential surface. Since the potential is the same at both points, we have:
\[ V_f = V_i \]

4. **Calculating Work Done**:
Substituting \( V_f \) and \( V_i \) into the work done equation:
\[ W = 1 \cdot (V_f - V_i) = 1 \cdot (0) = 0 \]
Therefore, the work done in moving a unit positive charge from one point to another over an equipotential surface is:
\[ W = 0 \]

### Final Answer:
The work done in moving a unit positive charge from one point to another over an equipotential surface is **zero**.