Work done is equal to change in potential energy.
Work done= pE-pEcos(theta).

**Electric Dipole in a Uniform Electric Field**

When an electric dipole is placed in a uniform electric field, it experiences a torque that tends to align the dipole moment with the electric field. The work done in rotating the dipole by an angle theta can be determined using the concept of torque and work.

**Torque on Electric Dipole**
- An electric dipole consists of two equal and opposite charges separated by a small distance, forming a dipole moment (P). The direction of the dipole moment is from the negative charge to the positive charge.
- When placed in a uniform electric field (E), the electric field exerts a force on the charges. The force on the positive charge is in the direction of the electric field, while the force on the negative charge is in the opposite direction.
- The forces create a torque on the dipole, which tends to rotate it. The torque (τ) acting on the dipole is given by the equation τ = P x E, where x represents the vector cross product.
- The torque causes the dipole to rotate until it aligns with the electric field or reaches a stable equilibrium position.

**Work Done**
- The work done in rotating the dipole can be calculated by considering the work done by the torque in rotating the dipole through an angle theta.
- The work done (W) is given by the equation W = τθ, where θ is the angle rotated by the dipole.
- Substituting the expression for torque (τ = P x E) into the equation, we get W = (P x E)θ.
- Since the dipole moment P and the electric field E are parallel in this case, the vector cross product P x E is equal to P * E * sin(90°) = P * E.
- Therefore, the work done can be simplified to W = P * E * θ.

**Conclusion**
In conclusion, when an electric dipole of moment P is placed in a uniform electric field E, and it is rotated by an angle theta, the work done in rotating the dipole is given by the equation W = P * E * θ. The work done is directly proportional to the dipole moment, the magnitude of the electric field, and the angle of rotation.