Wednesday, October 20, 2010

Irodov Problem 3.58

Let the dipole comprise of two charges q and -q seperated by a distance d as shown in the figure. Thus,

As described in problem 3.54, using the method of images, the effect of having a dipole p at a distance l from the conducting plane is same has having another dipole -p at a distance 2l from the original dipole, as illustrated in the figure.

The force acting on the dipole is the sum of the forces acting on the two charges q and -q of the original (not the reflection) dipole due to the charges in the image dipole.

Thus we have,


  1. sir, you have typo on the second line, there must be ...-1/(2l^2) insted of +

  2. I analysed this question and found that the electric field at a general point O(not on the centre) on the plane, and it turns out the net field is not zero if we take dipoles in opposite direction rather it comes out to zero (necessary for electrostatic condition) when the dipoles are in the same direction and answer in that case is same i.e. 3p^2/32(pi).e.l^4