The following pictures depict electric field lines for various charge configurations.

Figure (c) represents the electric field lines for three charges. If `q_2 = -20" nC"`, then calculate the values of `q_1 and q_3`.

Explanation

In the figure (c), the electric field lines start at `q_1 and q_3` and end at `q_2`. This implies that `q_1 and q_2` are positive charges. The ratio of the number of field lines is `| (q_1)/(q_2)| = (8)/(16) =| (q_3)/(q_2)| = (1)/(2)`, implying that `q_1 and q_3` are half of the magnitude of `q_2`. So `q_1 = q_3 = + 10" nC"`.