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Phys 4, Section 2
Feb 15,
2002
F = kq1q2/r2
E = F/q
Φ = IE
AdA
u = εoE2/2
V = W/q = -IEAds
C = Q/V C = εo
A/d
U = CV2/2 V = IR
P = I2R
k = 9 H 109
NAm2/C2
k = 1/(4πεo)
E = ρJ
J = I/A R =
ρL/A
I = dq/dt = nqvdA
e- = -1.6H10-19
C
dR/dT = αR
Series:
Reff = R1 + R2
+ ... 1/Ceff = 1/C1 + 1/C2+ ...
Parallel: 1/Reff = 1/R1
+ 1/R2 + ... Ceff = C1
+ C2 + ...
1. Electrostatics talks about two types of charge, differing in sign.
Which of the
following is true about the force between charges?
A) likes attract B) opposites attract
C) all charges attract each other
D) all charges repel each other
2. Whose law concerning electric charge is equivalent to Gauss's law of
electric
flux, though expressed in a completely different way?
A) Ohm B) Newton
C) Coulomb D) Volterra
E) Kirchhoff
3. What is the electric field of an iron nucleus at a distance of 6.0 ×
10-10 m from
the nucleus? [The atomic number of iron is 26.]
A) 1 B) 2 C) 3
D) 4 E) 5
× 1011 N/C
4. A disk with radius 0.10 m is oriented with its area vector at 30o
to a uniform
electric field E with magnitude 2.0 × 103
N/C. The area vector is on the same side
of the disk as the exiting field.
What is the electric flux through the disk?
A) 11 B) 26 C) 34
D) 41 E) 54
N·m2/C
5. Gauss's electric flux law applies to
A) only open surfaces B) only closed surfaces
C) any surface
6. A square insulating sheet 80.0 cm on a side has 7.5 nC of charge
spread
uniformly over its area. What is the electric field 0.1 mm above the
center of
the sheet?
1) 123 B) 213
C) 477 D) 662
E) 854
N/C
7. An electric field which falls off as 1/r is produced by a
A) point charge B) line of charge
C) sheet of charge
8. Two point charges of +12 nC and -12 nC are separated by 10 cm. What is
the
potential at a point located 4.0 cm outside and beyond the positive
charge on the
line passing through the two charges?
A) 870 B) -870
C) 1930 D) -1930
E) 0
V
9. A 5.8 μF parallel-plate air
capacitor has a plate separation of 5.0 mm and is
charged to a potential
difference of 400 V. What is the energy density in the
region between the
plates?
A) 28.3 B) 46.7
C) 56.6 D) 69.1
E) 93.4 × 10-3 J/m3
10. To increase the capacitive effect of two unequal capacitors, they
should be
joined in
A) series
B) parallel
11. What are the units of electromotiveforce ?
A) joules B) newtons
C) volts
D) amperes
12. A battery has an emf of 24.0 volts and an unknown internal resistance
r. When
an external resistor R is placed across the battery
terminals, the current through R
is 4.0 A and the voltage across R
is 21.2 V. What is the internal resistance of the
battery?
A) 0.1 B) 0.4
C) 0.7 D) 2.1
E) 3.2
ohms
13. A toaster using a nichrome heating element operates on 120 volts.
When it is
switched on at a room temperature of 20oC, the heating
element carries an initial
current of 1.35 A. A few seconds later the
current reaches the steady value of
1.23 A. What is the final temperature of
the element? [The temperature
coefficient of resistivity for nichrome is 4.5
× 10-4 (Co)-1.]
A) 50 B) 114
C) 183 D) 237
E) 312
oC
14. When charging an RC combination, which of the following decreases?
A) VC B) Q
C) C D) I
E) none of these
15. In the circuit at the right, what is the
value of the resistor R ?
A) 1 B) 2 C) 3 D) 4
E) 5 ohms
16. Which of the following depends only on the material involved, not the
geometry?
A) resistivity B) resistance
C) both D) neither
Answers: 1-b, 2-c, 3-a, 4-e, 5-b, 6-d, 7-b, 8-c,
9-a, 10-b, 11-c, 12-c, 13-d, 14-d, 15-e, 16-a
Last modified on May 07, 2002
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