A point charge (m = 1.0g) at the end of an insulating string of length 55cm is

Question:

A point charge (m = 1.0g) at the end of an insulating string of length 55cm is observed to be in equilibrium in a uniform horizontal electric field of 12,000N/C, when the pendulum€™s position is as shown in Fig. 16-66, with the charge 12cm above the lowest (vertical) position. If the field points to the right in Fig. 16-66, determine the magnitude and sign of the point charge.