Practice Problem on Potential Energy for Point Charges



                     Q1=-7 micro-C
                           o
                          / \
                         /   \
                        /     \
                       /       \
                      /         \
                     /           \
                    /             \
                   /               \
                  /                 \
   Q2=+2 micro-C o-------------------o Q3=-2 micro-C
                 |------- 4cm -------|
3 charges are arranged on an equilateral triangle as shown above. What is the potential energy of this charge configuration? Use the convention that U = 0 when the charges are infinitely apart. Specify your answer to three significant places.

ANSWER = ( U = -8.99e-1 J )