Question

Find the force between 2C and -1C separated by a distance 1m in air(in newton).

(a) 18 X 10^6

(b) -18 X 10^6

(c) 18 X 10^-6

(d) -18 X 10^-6

I have been asked this question during an interview.

Enquiry is from Coulomb Law topic in portion Electrostatic Fields of Electromagnetic Theory

Answer 1

Correct choice is (b) -18 X 10^6

The best I can explain: F = q1q2/(4∏εor^2) = -2 X 9/(10^-9 X 12) = -18 X 10^9.