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Physics 202 - First Exam February 6, 2007
Ignore the sign of the answer.
Answer ‘e’ is to be used as ‘none of the above’, ‘cannot be answered’, etc
You may not have a cell phone or any electronic device (other than a non-programmable
calculator with one memory and two pencils.
You may not have any paper (even blank) or notes at your seat.
You are to take your test questions home with you and only submit your answer sheets.
The +z direction is out of the paper toward your face and +x is to your right, +y up the page
towards the top.
Consider two charges: A of +5 C located on the y axis at y= -4m and B of -5 C located at y =
+4m.
1. What is the force between the two charges? a. 1.56 k b. 1.25 k c. ~ 0.39 k d. 0.8 k
2. What is the dipole that they constitute? a. ~40 b. 20
c. 1/20
3. What is the direction of this dipole? a. +y b. ~ -y c. +z
d. 1/40
d. -z
4. What is the magnitude of the electric field in the center of the two charges?
b. 1.25 k
c. 2.5 k
d. ~ 0.625 k
5. What is the direction of the electric field at that point?
a. ~ +y
a. 3.5 k
b. -y c. + x
d. - x
6. If a sphere of radius 3 m is centered on the A charge, then what is the flux thorough the
sphere? a. 3o b. ~ 5/o c. 3/o d. 5o
7. If an electric field of E= 12 is 25 degrees away from the +y axis toward the +x axis then
what is the torque on the dipole? a. 435 b. 466 c. ~ 203 d. 462
8. What direction is the torque?
a. into test paper b. ~ out of test paper c. +y d. -y
9. What is the electric potential at the point y=-8 due to the two charges above? a. 0.38 k
b. 4.5 k c. 0.45 k d. ~ 0.83 k
10. What is the magnitude of the potential energy of the system in problem?
b. ~ 3 k c. 2 k d. 1 k
11. Is this number
a. positive
b. ~ negative ?
a. 4 k
12. What is the electric field 8 m from an infinite straight line of charge when there is 12
Coulombs per meter? a. 0.67 k b. 1.5 k c. ~3k d. 6 k
13. If a parallel plate capacitor has plates of area 5 m2 and are 8 m apart, what is the
capacitance of the system if it has a charge of 20 C? a. 40/o
b. 40o
c. 1.6 o
d. ~ 0.625 o
14. What is the strength of the electric field inside the capacitor in the last problem?
b. ~ 4/o c. 8/o
d. 0
a. 2/o
15. What is the strength of the electric field a distance 0.5m outside of this parallel plate
capacitor? a. 2/o
b. 4/o c. 8/o
d. ~ 0
16. If a charge of 33 C is placed on a capacitor of voltage 3 V, what is the capacitance of the
system? a. ~ 11 b. 99 c. 0.33 d. 0.1
17. How much energy is stored in the system in the last problem. a. 99
d. 423.5
b. 33 c. ~ 49.5
18. If a dielectric material of value 3.5 is inserted fully into this parallel plate capacitor filling
the area between the plates then what is the new capacitance? a. 3.14 b. ~ 38.5 c.
115.5 d. 75.4
19. If a voltage of 12 V is applied to a resistor of 6 Ohms for 2 seconds, what is the resulting
current? a. 1 b. 4 c. 12 d. ~ 2
20. What is the power loss in the last problem?
a. ~ 24
b. 12
c. 4 d. 2
21. What is the resistance of the system shown with a 12 Ohm resistor in parallel with a 4
Ohm and 8 Ohm set in series? a. 32 b. 48 c. 96 d. ~ 6
22. What is the capacitance of the system shown with a 12 Farad capacitor in parallel with a
pair of 4 Farad and 8 Farad in series?
a. ~ 14.67 b. 12.5 c. 8.3 d. 3.8
23. If the resistively of tungsten 6.0E-8 then what is the resistance of a wire of radius 4cm
and a length of 70 m? a. 7.2E-8 b. 7.2E-4 c. ~ 8.4E-4 d. 7.2E-2
24. If the resistivity in the last problem is taken at 20 degrees Celsius and the temperature is
raised by 70 degrees Celsius with a temperature coefficient of resistivity of 4E-3 then
what is the new resistivity? a. ~ 7.68E-8 b. 6.67E-8 c. 1400 d. 2.8E.2
25. Consider two vectors A = (1,2,3) and B = (4,0,2). What is the length of A? a. 7.3 b.
4.3 c. 2.8 d. ~ 3.7
26. What is their dot product? a. 6 b. ~ 10 c. 8
 What is the angle between them? a. 52


28. What is the value of o? a. 8.89E-12
d. 12
b. ~ 53 c. 47
d. 46 
b. 8.86E-12 c. ~ 8.84E-12
d. 8.81E-12
29. Who identified lightning as being an electrical current in nature? a. ~ Franklin b.
Gauss c. Coulomb d. Ampere
30. Who used a torsion balance in their work? a. Franklin b. Gauss c. ~ Coulomb d.
Ampere
31. Whose law can be used to compute the value of the electric field for situations where the
geometry is highly symmetric and simple? a. Franklin b.~ Gauss c. Coulomb d.
Ampere
32. Where does the charge accumulate on a charged conducting surface? a. uniformly with
the same charge density b. greater charge density in areas of small curvature (ie flatter) c.
~ greater charge density in areas of high curvature d. it cannot be determined without
knowing the total charge density and the area