PHYS2424 - SPRING 2000
EXAM II - Part 1
NAME ______________________________________
SS# _________________________________________
I.
Multiple Choice
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(48 pts)
II.
Maxwell's Eqt.
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(32 pts)
III.
Drawings
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(15 pts)
IV.
Units
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(18 pts)
V.
Fill in the Blank
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Total Part I
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(137 pts)
Total Part II
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(200 pts)
Exam Total & Grade
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I.
Multiple Choice Problems ( 4 points each )
1.
At a particular instant, an electron experiences a force in the -y direction
while traveling in the uniform magnetic field shown below. What
direction is the electron traveling at this instant?
y
B
F
x
z
a)
-z direction
b)
-y direction
c)
d)
+x direction
e)
None of these.
2.
A particular RL circuit has a time constant of 10.0 s. What fraction of
the original current will flow through the inductor 20.0 s after the
inductor starts charging.
a)
0.135
b)
0.950
d)
0.100
e)
None of these
c)
-x direction
0.865
3.
The rms value of house voltage in much of Europe is 220 V. What is the
maximum voltage?
a)
440 V
b)
310 V
d)
160 V
e)
120 V
4.
For an inductor,
a)
the voltage lags behind the current.
b)
the current lags behind the voltage.
c)
the current and voltage are in phase.
d)
the current-voltage phase angle is greater than 90.
e)
the current-voltage phase angle is less than 90.
c)
220 V
5.
A conducting loop lies in the plane of this page and carries a clockwise
induced current. Which of the following could be true?
a)
A constant magnetic field is directed into the page.
b)
A constant magnetic field is directed out of the page.
c)
An increasing magnetic field is directed into the page.
d)
A decreasing magnetic field is directed into the page.
e)
A decreasing magnetic field is directed out of the page.
6.
A conducting loop around a bar magnet begins to move away from the
magnet. Which of the following statements are true?
a)
The magnet and the loop repel one another.
b)
The magnet and the loop attract one another.
c)
The magnet is attracted, but the loop is repelled.
d)
The magnet is repelled, but the loop is attracted.
e)
The magnet and loop neither attract nor repel one another.
7.
For the output current from the secondary coil of a transformer to be 10
times the input current to the primary coil, the ratio of the number of turns
N2/N1 must be
a)
100
b)
10
d)
0.1
e)
0.01
8.
The inductance of a coil is 5.00 H and the current through the coil is
16.0 A. If the current is uniformly reduced to zero in 4.00 milliseconds,
what is the average emf induced in the coil?
a)
80,000 V
b)
20,000 V
d)
2000 V
e)
None of these
c)
c)
1
8000 V
9.
At what frequency would the reactance (the magnitude of the impedance)
of a 1.0 mH inductor be twice that of a 10 F capacitor?
a)
10 kHz
b)
3.2 kHz
d)
1.6 kHz
e)
1.1 kHz
10.
The magnetic flux flowing through a conducting loop can be changed by
a)
changing the area of the loop.
b)
changing the magnitude of the magnetic field through the loop.
c)
changing the angle between the magnetic field and the plane of the loop.
d)
Answers B and C are correct.
e)
Answers A, B, and C are correct.
c)
2.2 kHz
11.
Two identical bar magnets are dropped from equal heights. Magnet A is
dropped from above bare earth, whereas magnet B is dropped from above
a metal plate. Which magnet strikes first? (neglect air friction)
a)
Magnet A
b)
Whichever has the N pole toward the ground
c)
Magnet B
d)
Whichever has the S pole toward the ground
e)
Both strike at the same time
12.
According to Maxwell's equations, the source of electric field circulation
is
a)
a constant current
c)
time-varying magnetic field d)
e)
capacitance
b)
a net charge
time-varying electric field
II.
Maxwell's Equations ( 4 points each )
A.
Write Maxwell's equations in the most general manner in differential form:
1)
Ampere-Maxwell Law
2)
Gauss' Law of Electrostatics
3)
Gauss' Law of Magnetism
4)
Faraday's Law of Magnetic Induction
B.
Write Maxwell's equations in the most general manner in integral form:
1)
Ampere-Maxwell Law
2)
Gauss' Law of Electrostatics
3)
Gauss' Law of Magnetism
4)
Faraday's Law of Magnetic Induction
III.
Drawings (3 pts each except #3 which is worth 6 pts)
1.
Draw the magnetic field lines for the perfect toroid whose cross sectional view is
shown below:
2.
Draw the direction of the current flowing through the loop to produce the
magnetic field lines shown in the diagram.
3.
Shown below is a picture from a cloud chamber in which three particles (A, B,
and C) are created. Given that an external magnetic field is directed into the page
as shown in the diagram, you are to determine whether each particle is positive,
negative, or neutral and fill in the appropriate blank.
A: ____________________
B: ________________________
C: ____________________
A
B
C
4.
Draw the magnetic field lines for an infinite wire with current flowing into the
page as shown in the diagram below.
IV.
Fill In The Appropriate Units (3 pts each)
1.
Impedance
2.
Magnetic Flux _____________________________________
3.
Inductance
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4.
Reactance
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5.
Magnetic Field _____________________________________
6.
Time Constant _____________________________________
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V.
Fill in the Blank (3 pts each)
1.
How many Gauss is 5.0 Tesla?_____________________________________
2.
Write the Biot-Savart Law
3.
Write Ampere's Law ____________________________________________
4.
Write the Lorentz Force Law ______________________________________
5.
Write the equation that defines a magnetic moment _____________________
6.
The magnitude of the magnetic moment due to the spin of an electron is called the
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7.
Write Stoke's Theorem
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8.
Write the formula for determining the resonance frequency of an LRC circuit
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