Question

The following questions use a central charge of q1=+2x10^-4C

1. What is the field strength at a distance of 5m from the central charge?
I got 7.2x10^4 However, I'm not sure which unit to use... is it joules?

2. What is the force acting on another charge (+5x10^-4C) which is 5m from the central charge?
I'm not sure which formula to use. Would it be Fe=(kq1q2)/r^2 ? It just doesn't seem right; would I need to use vectors to find the direction?

3. What is the electrical potential for the charge in question #2 if it is moved from infinity to a distance 3m from the central angle?
This confuses me because I thought it was 5m from the central charge, or is this different?

4. What is the difference in electrical potential if the charge from question #2 is moved from 10m away from the central charge to 2m away from it?

Answer 1

1. If you used E = k q/R^2, the field strength should be in Newtons per Coulomb or Volts per meter, which are the same thing

2. That is the correct formula

3. It's a different question, and location. The potential (in volts) is
k q1/ R , regardless of the value of q2

4. Compute the potential difference between the two locations

It is not clear if, when they are asking for electric potential (J/C), they really want potential energy (J)