4. (0.5 point each, 2.0 points total) For each pair of charges, draw a force vector on each charge to show the electric force acting on that charge. The length of each vector should be proportional to the magnitude of the force. Each + and - symbol represents the same quantity of charge.
5. (2.0 points total) Each of the following parts involves a comparison of the net electric force exerted on a positive charge +q in two different cases.
(a) In case A and B shown below there are two positive point charges +Q each a distance s away from a third point charge +q. On the +q charge, draw the electric force vectors due to the two +Q charges, then draw and label the net electric force vector. Is the magnitude of the net electric force on the +q charge in case A greater than, less than, or equal to the net electric force on the +q charge in case B? (Hint: refer to the last question of Electric Field Hockey Simulation.)
(b) In case C, two positive point charges +2Q are each a distance s away from a third positive point charge +q. In case D, four positive point charges +Q are each at a distance s away from a fifth positive point charge +q. (The angle α shown is the same in both cases.) Is the net electric force on the +q charge in case C greater than, less than, or equal to the net electric force on the +q charge in case D? (0.5 point)
Explain. (1.0 point)