1. Two point charges are on the y axis. A 3.80-µC charge is located at y = 1.25 cm, and a -2.18-µC charge is located at y = -1.80 cm.
(a) Find the total electric potential at the origin.
V
(b) Find the total electric potential at the point whose coordinates are (1.50 cm, 0).
2. An amount of charge ±Q is placed on the plates of a parallel-plate capacitor so that the potential across the plates is ?Vinit. The capacitor is then disconnected, and the separation between its plates is increased by a factor of three. If the charge on the plates is ±34 ?C while the final capacitance is 6.0 multiply.gif 10-9 F, what was ?Vinit?