# Electric Potential, spherical shell: Multiple Choice

by TwinGemini14
Tags: choice, electric, multiple, potential, shell, spherical
 P: 34 A non-conducting, spherical shell centered at the origin has radius r1 and total charge -Q, where Q is a positive value. (DO NOT ASSUME THE POTENTIAL AT INFINTIY IS ZERO!) http://i662.photobucket.com/albums/u...Cpotential.gif 1) The electric potential just outside the surface of the shell is __________ the electric potential infinitely far from the shell. A) higher than B) lower than C) equal to ------ This problem stumped me. I figured that the electric potential outside the sphere was... V = -Q/(4*pi*EpsilonNot*r) So as r grows, the potential actually gets higher. So the answer is B. ----- 2) If a negative charge outside the shell is moved closer to the shell, the potential energy of the system will __________. If a positive charge outside the shell is moved closer to the shell, the potential energy of the system will __________. A) decrease, increase B) increase, stay the same C) increase, decrease ----- Since the force and displacement vectors are acting in opposite directions, the total work decreases. PE = -W, so then that means that the potential energy increases. The opposite is true with the positive charge. So the answer is C. -------------------- Can somebody please confirm these answers? I would like to know if I messed up some logic along the way. Thanks in advance!