Considering Figure 18.42, suppose that q_a = q_d and q_b= q_c. First show that q is in static equilibrium. (You may neglect the gravitational force.) Then discuss whether the equilibrium is stable or unstable, noting that this may depend on the signs of the charges and the direction of displacement of q from the center of the square.

Transcribed Image Text:

qa O qc Oq 9b O qa