An electric dipole has the magnitude of its charge as `q` and its dipole moment is `p`. It is placed in a uniform electric field `E`. If its dipole moment is along the direction of the field, the force on it and its potential energy are respectively

Options

A. q. E and p. E
B. zero and minimum
C. q. E and maximum
D. 2q. E and minimum

Explanation

To solve the problem, we need to determine the force on an electric dipole and its potential energy when it is placed in a uniform electric field, with the dipole moment aligned with the field.

### Step-by-Step Solution:

1. **Understanding the Electric Dipole**:
An electric dipole consists of two equal and opposite charges, +q and -q, separated by a distance \( d \). The dipole moment \( p \) is defined as:
\[ p = q \cdot d \]
The dipole moment is a vector quantity that points from the negative charge to the positive charge.

2. **Dipole in an Electric Field**:
When an electric dipole is placed in a uniform electric field \( E \), the dipole experiences forces on both of its charges. The force on the positive charge (+q) is:
\[ F_+ = qE \]
The force on the negative charge (-q) is:
\[ F_- = -qE \]

3. **Net Force on the Dipole**:
The net force \( F_{net} \) acting on the dipole is the vector sum of the forces on the positive and negative charges:
\[ F_{net} = F_+ + F_- = qE - qE = 0 \]
Therefore, the net force on the dipole in a uniform electric field is zero.

4. **Potential Energy of the Dipole**:
The potential energy \( U \) of an electric dipole in an electric field is given by the formula:
\[ U = -\vec{p} \cdot \vec{E} = -pE \cos \theta \]
where \( \theta \) is the angle between the dipole moment \( \vec{p} \) and the electric field \( \vec{E} \). In this case, since the dipole moment is aligned with the electric field, \( \theta = 0^\circ \).

5. **Calculating Potential Energy**:
Since \( \cos 0^\circ = 1 \), the potential energy becomes:
\[ U = -pE \cdot 1 = -pE \]
This indicates that the potential energy is at a minimum when the dipole moment is aligned with the electric field.

### Final Answers:
- **Force on the dipole**: \( F_{net} = 0 \)
- **Potential energy**: \( U = -pE \)