Question

A ring of charge with radius 1.5 cm and a charge of 100nC has the electric field along the primary axis of the ring as E=kQx/(R^2+x^2)^3/2

1. find electric field 2.25 cm from the center of the ring along the primary axis
2. what force would a charge of -5nC experience at this point
3. what point charge would you have to place at x=-5cm to make the electric field zero at this location?

Answer 1

The electric field along the primary axis is given by the equation

Here, Q is 100nC

When x=2.25cm, Electric field is given by

We directly substitute the values to the equation because it is given as the electric field along the primary axis. here, we dont have to split it into its components and analyse the field.

2) a charge of -5nC would experience a force of

3)The question is a bit confusing. There can be no point charge configuration, which we can establish at x=-5cm, so that the net field due to both the ring and the charge and the point charge would add up to zero. this is because, if we put a point charge at x=-5cm, then the field due to that charge will infinity at that specific point, as and if r =0. then E would be infinity.

But i think that the question was a sub part of Q no.1. If we were to put a point charge at x=-5cm and to make the field at x=2.25cm zero, that can be done.

The field due to the ring configuration at x=2.25cm is 9.0793*10^5N/C. that mean the field due to the point charge at x=-5cm should be equal to -9.0793*10^5N/C