PHYSICS · Multi-part · CBSE · Physics · Electrostatic Potential and Capacitance · Electrostatic Potential and Capacitance
Problem
Two point charges, +q and –q, are held fixed in space so that the distance r between them can be varied. The electric potential energy of the system is given by U(r). A student is asked to analyze how U depends on r for this pair of charges.
(a) On the axes you will provide in your answer booklet, sketch a qualitative graph of U versus r for r > 0 up to several multiples of a characteristic length r0. Label the vertical axis with appropriate signs of U and the horizontal axis with r.
(b) Describe how the sign and relative magnitude of the electric force between the charges are related to features of your graph in part (a). In your explanation, include references to both the sign of the force and where its magnitude is greatest.
(c) Identify any horizontal or vertical asymptotes of the graph and explain their physical meaning for the charged system.
(d) Suppose the charges are released from rest at a separation r1 that is half the value of r0. Without doing explicit calculations, predict qualitatively whether mechanical energy is conserved as the charges move and explain how your graph supports your answer.