An electric dipole is held in a uniform electric field. Show that the net force acting on it is zero. The dipole is aligned parallel to the field. Find the work done in rotating it through the angle of 180 degrees.
Step 1: Dipole in a uniform electric field
Step 2: The net force acting on a dipole
In a uniform electric field , the force exerted on is and the force exerted on is .
So, the net force exerted on the dipole is,
Diagram
Therefore, the net force acting on a dipole is zero.
Step 3: Work done to rotate a dipole in an electric field
As we know know that the work done to rotate a dipole is at an angle is
Now work is done to rotate the dipole at an angle of 180 is,
Therefore, the work done in rotating it through the angle of 180 degrees is .