Physics, Electric Fields, Question is in the description

Question

What is the relationship between the electric field strength and the distance from the point source? If you move three times farther away, what will happen to the field strength?

Answer 1

By definition, E= F/Q (the electric field strength equals to electric force over charge creates the field).

Electric force F=kQq/R^2 , where R is distance between Q and q.

Then E=kq/R^2. If the distance will be increase 3 times, that means, the force will decreased by 3^2=9 times.

Hence, the electric field strength E will be decreased by the same times (remember k is constant and Q unchanged).

Finally, E will decrease 9 times.