An insulating spherical shell with inner radius 25.0 cm and outer radius 60.0 cm carries a charge of + 150.0 µC uniformly distributed over its outer surface (see Exercise 23.43). Point a is at the center of the shell, point b is on the inner surface, and point c is on the outer surface.
(a) What will a voltmeter read if it is connected between the following points: (i) a and b; (ii) b and c; (iii) c and infinity; (iv) a and c?
(b) Which is at higher potential: (i) a or b; (ii) b or c; (iii) a or c?
(c) Which, if any, of the answers would change sign if the charges were - 150 µC?