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Scheller
Physics 176
Exam #2
Spring 2013
9 a.m.
Read these instructions carefully. Write your name in the upper right hand corner of this page. Do all your
work on the test pages. Put all final answers in a box. Answers without units are incomplete.
Constants:
qproton= +1.6x10-19 C
qelectron= -1.6x10-19 C
mp=1.67x10-27 kg
me=9.1x10-31 kg
1) Using the picture to the right, answer the following:
a) What is the potential difference between points A & B?
k=9x109 N m2/C2
cu=1.7x10-8 m
B
A
40 cm
60 cm
30 cm
750,000V
26 cm
26 cm
Q2=-50 uC
Q1=+50 uC
b) How much work would be required to bring a +20 uC charge (mass= 3 grams) from a distant location to
point A?
15 J
c) What would be the velocity of the +20 uC charge at point B if released from point A at rest?
100 m/s

a) If the plates are separated by 15 mm, what is the strength and
direction of the electric field between them?
5.66e5 Volts/m downward
15mm
2) A 2 uF capacitor stores 36 J of electrical energy.
b
10
m
m
48o
a
--------b) If an electron were released from rest at point a, what speed would it have upon reaching point b?
3.85e7 m/s
c) How much charge is stored on this capacitor?
.017 Coulombs
3) In the ocean, an electric eel can generate a potential difference of 500 volts between its ends, delivering a
current of 0.7 amps for a 0.001 second duration.
a) What is the power output of this eel?
b) How much energy does he deliver during this event?
c) How much charge flows during this time?
350 Watts
.35 Joules
7e-4 Coulombs
4) When you turn the ignition key in your car, the battery can deliver 300 A of current to the starter motor. If
the copper wires from the battery to the starter have a length of 0.95 meters, what must be the minimum
diameter of the wires if the voltage drop along the wires themselves is less than 0.6 volts?
.0032 m diameter
5) For the circuit to the right, find the current through each
resistor.
2.4 
6
7
9
I(6)= 1.03 amps
I(5)= 1.03 amps
I(8)= .456 amps
I(2.4)= .574 amps
I(7)= .323 amps
I(9)= .252 amps
15 V
8
5
6) For the circuit to the right, use Kirchoff’s laws to find:
a) The currents I1, I2, & I3 through each resistor as shown.
b) The terminal voltage of the 28 Volt battery (internal
resistances of batteries are shown).
5
6
4
28V
r=1
I1=1.5 amps
I2= -.2 amps
I3= 1.3 amps
Vt= 26.5 volts
I1
10 
10 V
I3
8
I2
r=1