Question

Assume that we have a fixed charge of 24C. Another charge 8C is moved from a distance of 4m away to a distance of 3m away. Find the work that is put in. (Hint: This work must be equal to the change in potential energy!

Answer 1

PE = K Q1 Q2 / R potential energy at distance R

W = PE2 - PE1

W = K Q1 Q2 (1/3 - 1/4) = K Q1 Q2 * .083 / m

W = 9.00E9 farads/m * 8 * 24 c^2 * .083 / m = 1.43E11 joules

Change in potential is positive because positive charges are being brought closer