Monday, January 25, 2010

Irodov Problem 3.11

Consider an infinitesimally small section of the wire of length dx. The charge in this infinitesimally small section of wire will be,

The force acting on this infinitesimally small section of the wire due to the ring will be,

The electric field E due to the ring at a distance x along the axis has already been derived in the solution to problem 3.9 in Eqn 4 as,

The total force acting on the wire is thus given by,


  1. can u plz integrate second last term....

  2. multiply and divide by 2 in numerator... it reduces to the form----f'(x)/[f(x)]^n which can be easily integrated...

  3. An easier method would be to find the axial component of the force on dq element of the ring considering the wire as semi infinite. Since that force is same for all dq, no integration is required. Replace dq by q to get the answer.