Final_Review - Clark Musselman, Ph.D.

Spring 2015 - Physics 162 - Final Exam Review
1. In the circuit shown in the figure, all the lightbulbs are identical. Which
of the following is the correct ranking of the brightness of the bulbs?
(a) B and C have equal brightness, and A is the dimmest.
(b) A and B have equal brightness, and C is the dimmest.
(c) A is brightest, C is dimmest, and B is in between.
(d) A is the brightest, and B and C have equal brightness but less than
A.
(e) All three bulbs have the same brightness.
2. A resistor is made out of a long wire having a length L. Each end of the
wire is attached to a terminal of a battery providing a constant voltage V0 .
A current I flows through the wire. If the wire were cut in half, making
two wires of length L/2, and both wires were attached to the battery (the
end of both wires attached to one terminal, and the other ends attached
to the other terminal), what would be the total current flowing through
the two wires?
(a) 4I
(b) 2I
(c) I
(d) I/2
(e) I/4
3. Two light bulbs, B1 and B2, are connected to a battery having appreciable
internal resistance as shown in the figure. What happens to the brightness
of bulb B1 when we close the switch S?
(a) The brightness of B1 increases permanently.
(b) The brightness of B1 decreases permanently.
(c) The brightness of B1 does not change.
(d) The brightness of B1 increases temporarily but gradually decreases
back to its original brightness.
(e) The brightness of B1 decreases temporarily but gradually increases
back to its original brightness.
4. A +2.0 nC charge is at the origin and a -4.0 nC charge is at x = 1.0 cm.
(a) At what x-coordinate could you place a proton so that it would experience no net force?
(b) Would the net force be zero for an electron placed at the same position? Explain.
5. What is the speed of an electron that has been accelerated from rest
through a potential di↵erence of 1000 V?
6. Wires 1 and 2 are made of the same metal. Wire 2 has twice the length
and twice the diameter of wire 1. What are the ratios
(a) ⇢2 /⇢1 of the resistivities and
(b) R2 /R1 of the resistances of the two wires?
Answers:
1. D
2. A
3. B
4. (a) x =
2.4 cm
(b) Yes
5. 1.87 ⇥ 107 m/s
6. (a) 1
(b) 1/2
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