Download Following are some practice problems

Following are some practice problems
Each multiple choice question is worth 5 points.
Choose only one answer for each question.
Problem 1. A dipole is located at the corner of a square whose side has length d,
as shown in the diagram below.
s
-
A
+
d
B
Which arrow in the rosette below best represents the direction of the electric field
at location A, due to the dipole?
1.
2.
3.
4.
5.
a
c
d
f
j
CORRECT
Problem 2. A sphere with radius 2 cm is placed at a location near a
point charge. The sphere has a charge of -9 x 10-10 C spread uniformly
over its surface. The electric field due to the point charge has a magnitude
of 520 N/C at the center of the sphere. What is the magnitude of the force
on the sphere due to the point charge?
1.
2.
3.
4.
5.37e-09 N
4.68e-07 N
8.23e+08 N
3.07e+06 N
CORRECT
Problem 3. Atom A is easier to polarize than atom B. Which atom,
A or B, would experience a greater attraction to a point charge
a distance r away?
1.
2.
3.
4.
A CORRECT
B
Same
The polarization does not matter
Problem 4. If the distance between a neutral atom and a point charge
is quadrupled (i.e. multiplied by 4), by what factor does the force
on the atom by the point charge change?
(New force / Old force) = 1.
2.
3.
4.
0.0016
16
0.000977
0.08
CORRECT
Problem 5. A metal ball with diameter of a half a centimeter and
hanging from an insulating thread is charged up with 1010 excess
electrons. An initially uncharged identical metal ball hanging from
an insulating thread is brought in contact with the first ball, then
moved away, and they hang so that the distance between their
centers is 20 cm. What is the magnitude of the electric force one ball
exerts on the other?
1.
2.
3.
4.
9.23e-05 N
4.01e+10 N
2.08e-02 N
1.44e-07 N
CORRECT
Problem 6. Breakdown field strength for air is roughly 3 106 N/C.
If the electric field is greater than this value, stray free electrons
(due to ionization of air molecules by cosmic rays) will be accelerated
to high enough energies to trigger a chain reaction.
How much
excess charge can you put on a metal sphere of 12 cm radius without
causing breakdown in the neighboring air, which would discharge
the sphere?
1.
2.
3.
4.
4.80e-06 C
9.03e-03 C
5.09e-01 C
2.16e+02 C
CORRECT
Problem 7. The figure shows two thin plastic spherical shells (shown in
cross section) that are uniformly charged. The center of the larger sphere
is at < 0, 0, 0 >; it has a radius of 12 cm and a uniform positive charge of
4 x10-9 C. The center of the smaller sphere is at < 25, 0, 0 > cm; it has a
radius of 3 cm and a uniform negative charge of -2 x10-9 C. What is the
electric field at location A (6cm to the right of the center of the large sphere)?
Neglect the small contribution of the polarized molecules in the plastic.
1.
2.
3.
4.
<50,0,50> N/C
<0,50,50> N/C
<0,0,500> N/C
<500,0,0> N/C
CORRECT
Problem 8. Two aluminum blocks, A and B, are initially neutral. They
have insulating handles, which are not shown. This sequence of
events occurs:
Time t1:
Neutral Blocks Touching
A
B
B
Time t2:
Positive charge near A
+
A
Time t3:
Move blocks apart
+
A
B
A
B
Time t4:
Take positive charge away
After time t4, what is the net charge on block A?
1.
2.
3.
4.
Positive
Negative
CORRECT
Neutral
Need more information to answer