Dr. Bullock
FORM -A
Physical Principles II –Exam 2
NAME:
Each question is worth 5 points distribute each point on one line of the scantron.
Question 1-5
The diagram shows four 6-μF capacitors. The capacitance between points a and b is:
A. 3 μF
B. 4 μF
C. 6 μF
D. 9 μF
E. 1 μF
Question 6-10
“The sum of the emf’s and potential differences around a closed loop equals zero” is a
consequence of:
A. Newton’s third law
B. Ohm’s law
C. Newton’s second law
D. conservation of energy
E. conservation of charge
Question 11-15
A charged capacitor is being discharged through a resistor. At the end of one time
constant the charge has been reduced by (1 − 1/e) = 63% of its initial value. At the end of
two time constants the charge has been reduced by what percent of its initial value?
A. 82%
B. 86%
C. 100%
D. Between 90% and 100%
E. Need to know more data to answer the question
Physical Principles II –Exam 2
Dr. Bullock
FORM -A
Question 16-20
The time constant RC has units of:
A. second/farad
B. second/ohm
C. 1/second
D. second/watt
E. none of these
Question 21-25
An electron moves in the negative x direction, through a uniform magnetic field in the
negative y direction. The magnetic force on the electron is:
A. in the positive z direction
B. in the negative z direction
C. in the positive y direction
D. in the negative y direction
E. in the negative x direction
Question 26-30
Consider a uniform magnetic field directed from left to right. In which direction will a
proton moving at a speed v from left to right be accelerated?
A. North
North
B-Field
B. South
East
C. East
D. West
E. none of these
+
+
West
v
South
Physical Principles II –Exam 2
Dr. Bullock
FORM -A
Question 31-35
Which of the following will produce a magnetic field?
I.
A current-carrying wire
II.
Moving a wire through a field free region
III.
Electrons orbiting a nucleus
A. I only
B. II only
C. I and III only
D. II and III only
E. I, II, and III
Question 36-40
An electron and a proton each travel with equal speeds around circular orbits in the same
uniform magnetic field, as shown in the diagram (not to scale). The field is into the page
on the diagram. Because the electron is less massive than the proton and because the
electron is negatively charged and the proton is positively charged:
A. the electron travels clockwise around the smaller circle and the proton travels
counterclockwise around the larger circle
B. the electron travels counterclockwise around the smaller circle and the proton travels
clockwise around the larger circle
C. the electron travels clockwise around the larger circle and the proton travels
counterclockwise around the smaller circle
D. the electron travels counterclockwise around the larger circle and the proton travels
clockwise around the smaller circle
E. the electron travels counterclockwise around the smaller circle and the proton travels
counterclockwise around the larger circle
Physical Principles II –Exam 2
Dr. Bullock
FORM -A
Question 41-45
When electric current in two parallel wires is flowing in the directions shown below, the
wires tend to:
I1
I2
A. repel each other
B. attract each other
C. exert no force
D. spin
E. none of these
Question 46-50
The figure shows a uniform magnetic field B directed to the left and a wire carrying a
current into the page. The magnetic force acting on the wire is:
A. toward the right
B. toward the bottom of the page
C. toward the left
D. toward the top of the page
E. zero
Question 51-55
The magnetic field outside a long straight current-carrying wire depends on the distance
R from the wire axis according to:
A. R
B. 1/R
C. 1/R2
D. 1/R3
E. 1/R3/2
Dr. Bullock
FORM -A
Physical Principles II –Exam 2
Question 56-60
A 2-T uniform magnetic field makes an angle of 30◦ with the z axis. The magnetic flux
through a 3-m2 portion of the xy plane is:
A. 2.0Wb
B. 3.0Wb
C. 5.2Wb
D. 6.0Wb
E. 12Wb
Question 61-65
Faraday’s law states that an induced emf is proportional to:
A. the rate of change of the magnetic field
B. the rate of change of the electric field
C. the rate of change of the electric flux
D. the rate of change of the magnetic flux
E. zero
Question 66-70
A long straight wire is in the plane of a rectangular conducting loop. The straight wire
carries a constant current i, as shown. While the wire is being moved toward the rectangle
the current in the rectangle is:
A. counterclockwise
B. clockwise
C. counterclockwise in the left side and clockwise in the right side
D. clockwise in the left side and counterclockwise in the right side
E. zero
Dr. Bullock
FORM -A
Physical Principles II –Exam 2
Question 71-75
The figure shows a bar moving to the right on two conducting rails. To make an induced
current i in the direction indicated, a constant magnetic field in region A should be in
what direction?
A. Right
B. Left
C. Into the page
D. Out of the page
E. Impossible; this cannot be done with a constant magnetic field
Dr. Bullock
FORM -A
SHOW ALL YOUR WORK!
Physical Principles II –Exam 2
NAME
(10 POINTS)
A metal bar of mass m and length L is suspended from two conducting wires. A uniform
magnetic field of magnitude B points vertically downward. Find the angle  the
suspending wires make with the vertical when the bar carries a current I.
Dr. Bullock
FORM -A
SHOW ALL YOUR WORK!
Physical Principles II –Exam 2
NAME
(10 POINTS)
The equivalent capacitance of the capacitors shown is 9.22 F. Find the value of
capacitance C.