Question

1. (18.3.25) Point charges of 5.00 pC and-3.00 μC are placed 0.250 m apart. (a) Where can a third charge be placed so that the net force on it is zero? (b) What if both charges are positive? 2. (18.8.51) (a) What is the electric field 5.00 m from the center of the terminal of a Van de Graaf with a 3.00 mC charge? Note that the field is cquivalent to that of a point charge at the center of the terminal. (b) At this distance, what force does the field exert on a 2.00 μC charge on the Van de Graaf's belt?

Answer 1

Ans

1) a) Since the charges are of opposite sign and 5 uC is greater in magnitude than -3 uC. So the third charge is to the right of both charges so that the net force on it is zero. We use the Coulomb's law to get the force on the charge, then we find the position of the charge.

b) This time both charges are positive, so the third charges must be placed in between them.

Since the charges are of opposite sign and 5 uC is greater in magnitude than -3 uC. So the third charge is to the right of both charges so that the net force on it is zero. We use the Coulomb's law to get the force on the charge, then we find the position of the charge. b) This time both charges are positive, so the third charges must be placed in between them. A) Consider the figure shown Let a_3 be at x distance to the right of q_1 Finding x such that the net force on q_3 = 0 Net force on q_3 = F-1 + F-2 = 0 F-1 = due to (q_1 = 500 mu C) F-2 = due to (q_2 = -300 mu c) F-1 = -F-2 rightarrow F-1 = F_2 K Vertical-bar q_1 q_3 Vertical-bar /x^2 = k Vertical-bar q_2 q_3 Vertical-bar /(x - 0. 250)^2 Vertical-bar q_1 Vertical-bar /x^2