Unit 2. Electricity and Magnetism
I. Electrostatics
Questions 1 and 2 refer to the image below:
Two point charges, +2
Q
and -
Q
, are placed on the y-axis a distance
d
from the origin, as shown above. Point
P
is located on the x-axis a distance
d
to the left of the origin.
1.
Which of the following vectors could indicate the direction of the electric field at point
P
due to the two point charges?
A
B
C
D
E
Questions 2 and 3 refer to the statement below:
Each square plate of a parallel plate capacitor has length
s
; the plates are separated by a distance
a
across a vacuum. The plates are directly connected to opposite sides of a battery of EMF
V
.
2.
If
k
represents the Coulomb's law constant
,what is the electric potential at point
P
due to these two point charges?
3.
An electric field points horizontally in a region of space in which the electric potential decreases linearly from 30 V to 20 V over a horizontal distance of 2 m. What is the magnitude of the electric field in this region?
5 N/C
10 N/C
20 N/C
30 N/C
none of the above; the electric field varies in this region.
Questions 4 and 5 refer to the statement below:
A spherical cloud of radius
R
and charge contains total charge +
Q
distributed nonuniformly. The charge density varies according to the equation
, where
r
represents the distance from the center of the sphere.
4.
A test charge with charge -
q
and mass
m
is released from rest a distance 2
R
from the center of the sphere. Which of the following represents the speed of the test charge when it enters the cloud?
5.
Which of the following is the amount of charge enclosed by a spherical Gaussian surface of radius
a
<
R
?
6.
An electron with an initial velocity
v
is projected into the electric field
E
, as shown in the above diagram. The trajectory of the electron within the electric field would be best described as a portion of which of the following:
circle
parabola
helix
hyperbola
straight line
7.
A semicircular rod of uniform linear charge density
λ
and radius
R
sits with its center at the origin, as shown above. What is the electric potential at the origin due to this rod?
Monera
Protista
Fungi
Plantae
Animalia
Questions 8 and 9 refer to following text:
An isolated point charge can be surrounded by one of three surfaces, each centered upon the charge:
I. A sphere of radius R
II. A cube of side length 2R
III. A cylinder of radius R and height 2R
8.
How does the net flux through each of these surfaces compare?
I is greatest
II is greatest
III is greatest
II and III are the same, and are greater than I
I, II, and III are all the same
9.
Which of these surfaces could be used with Gauss's law for a straightforward analytic calculation of the field of the enclosed charge as a function of the distance
r
from the charge?
I, II, or III
II or III only
I or II only
I only
II only
10.
Two parallel plates are connected to a 12 V potential difference. Electron
A
is placed halfway between the plates; another electron
B
is placed one quarter of the way between the plates, closer to the positive plate. How does the force on each electron compare?
The force on electron
A
is twice as strong as on electron
B
.
The force on electron
B
is twice as strong as on electron
A
.
The force on electron
A
is four times as strong as on electron
B
The force on each electron is the same
The force on electron
B
is four times as strong as on electron
A
.
