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Spring 2015 - Physics 162 - Exam 1 Review
1. A plastic rod that has been charged to 3 nC touches a metal sphere.
Afterward, the rods charge is 2 nC.
(a) What kind of charged particle was transferred between the rod and
the sphere, and in which direction? That is, did it move from the
rod to the sphere or from the sphere to the rod?
(b) How many charged particles were transferred?
2. What is the force F~ on the 5.0 nC charge in the figure?
3. In the figure below, what is the dipole moment? What are the strength
and direction of the electric field at the position indicated by the dot in
the figure?
Answers:
1. (a) Electrons were transferred from the sphere to the rod.
1
(b)
⇥ 1010 electrons were transferred.
1.60
2.
• F~+ = (18 ⇥ 10 5 N )( 3/5ˆı
• F~ = 25 ⇥ 10 5 Nˆı
• F~ = F~+ + F~
3. p~ = 3.0 ⇥ 10
10
Cm |ˆ,
~ dipole ⇡
E
4/5ˆ
|)
22, 000 N/C |ˆ
Full solutions are posted below.