Three point charges are fixed on a straight line with equal spacing between…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Three point charges are fixed on a straight line with equal spacing a between successive charges. The charges, in order from the origin, are:
• q1=q at x=0
• q2=kq at x=a
• q3=4q at x=2a
(Here q>0 and k is a real number.)
(i) Write an algebraic expression for the net electrostatic force acting on q1 in terms of q, k, a, and the electrostatic constant ke.
(ii) Determine the value of k for which the net force on q1 becomes zero.
(iii) Using the value of k obtained in part (ii), calculate the magnitude and direction of the net electrostatic force acting on the charge q3 at x=2a.