PHYS 1112 Module 1.2

Conductors, Insulators, and Charging by Induction

Practice!

Practice 1.2.1

Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D).

A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D.
Check your answer here: strongly attractive
Practice 1.2.2

Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D).

A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D.
Check your answer here: weakly attractive
Practice 1.2.3

Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D).

A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D.
Check your answer here: attractive
Practice 1.2.4

Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D).

A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D.
Check your answer here: neither attractive nor repulsive
Practice 1.2.5

Two uncharged metal spheres located on top of insulating poles are initially in contact as shown.  A positively charged insulator is brought close to sphere 1 without touching and removed, and then the spheres are separated.
Check your answer here: Q1 = 0 and Q2 = 0
Practice 1.2.6

Two uncharged metal spheres located on top of insulating poles are initially in contact as shown.  A positively charged insulator is brought close to sphere 1 without touching and then the spheres are separated before the positively charged insulator is removed.
Check your answer here: Q1 = – and Q2 = +