PES 1120 General Physics II
Practice Exam 2
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One (3” x 5”) index card may be used for formulas or other notes or diagrams.
Definitions & Concepts (2 pts each)
1. What units will result from multiplying Amperes by Volts?
a. Farads
b. Newtons
c. Watts
d. Joules
2. A negative charge is brought from very far away until it is near a positively charged sphere.
Which of the following is true?
a. Work is done by the system (potential drops)
b. Work is against the system (potential rises)
c. No work is done
3. Equipotential lines can cross each other.
a. True
b. False
Applications
4. Two particles, one of charge +4 pC and the other of -2 pC are placed 1 cm apart.
a. How much energy was involved in constructing this configuration?
b. What is the potential at a point 1 cm equidistant from both charges?
5. A conducting sphere of 0.1 m radius has 1 nC of charge placed on it. What is the voltage at a
point 0.2 m from the surface of the sphere if voltage at infinity is taken to be zero?
6. If 5 mA of current flow through a wire of diameter 1 mm, what is the current density through
the wire?
R. Gist
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Long Semester Ver. C, Rev 2
PES 1120 General Physics II
Practice Exam 2
7. A large, flat plate has 6 nC/m2 of charge on its surface. What is the voltage difference between
points A and B that are a distance of 1 cm and 2 cm, respectively, from the surface?
8. What is the equivalent capacitance of the combination shown?
9. Air-filled parallel plate capacitor
a. The capacitor is constructed with a capacitance of 6F. If the plates are 0.1 mm apart,
what is the area of one of the plates?
b. A voltage source of 12 V is connected across the capacitor. How much charge
eventually moves onto the positive plate?
c. How much energy is now contained in the capacitor?
d. Some Pyrex glass (dielectric constant of 5.6) is inserted between the plates and the
capacitor is again connected to the same voltage source. What is the new capacitance?
10. A rod of 2.0-m length and a square (2.0 mm x 2.0 mm) cross section is made of a material with
–8
a resistivity of 6.0 x 10   m at 20o Celcius.
a. What is the resistance of the rod at this temperature?
b. If a potential difference of 0.50 V is placed across the ends of the rod, what is the initial
current?
c. At what rate is heat generated (i.e. power used) in the rod the instant current begins to
flow?
d. The material then heats up to an operating temperature of 500 degrees Celcius. The
temperature coefficient of the material is 0.5 x 10-3 Kelvin-1. What is the operating
resistance?
Constants
o
kE
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Permittivity of free space
Coulomb’s constant
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8.854 x 10-12 C2/(N*m2)
8.98 x 109 N*m2/C2
Long Semester Ver. C, Rev 2