Two identical point charges of +Q coul are separated by a distance of 10 cm. (a) Calculate the work done per unit change to bring up another charge from far
away along the perpendicular bisector of the line joining the two charges to
the point point midway between the charges.
(b)If one of the two charges in part(a) is changed from +Q to –Q, calculate the
work done per unit charge to bring up a charge to the same position as
above.

An external consultant recommends that a plant installs a bank of capacitors for power factor correction. this will reduce the peak electrical demand charges by an average of 93 kw every month. the plant current pays $13 per kw in peak demand charges. the capacitor bank will include 223 kw of fixed capacitors, and 183 of variable capacitors. the fixed capacitors cost $59 per kw, and the variable capacitors will cost $65 per kw. the consultant charges 21% of the equipment costs to install the capacitors. because this project will reduce the demand for the electric utility, they are prepared to provide a one-time rebate of $42 per kw of reduced demand. what is the simple payback period for this project (in years)?