TIME
OF
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NAME____SOLUTION_________________________
DEPARTMENT OF NATURAL SCIENCES
PHYS 1112, Exam 3
Version 1
Total Weight: 100 points
Section 1
April 23, 2013
1.
Check your examination for completeness prior to starting. There are a total of nine (9)
problems on seven (7) pages.
2.
Authorized references include your calculator with calculator handbook, and the Reference
Data Pamphlet (provided by your instructor).
3.
You will have 75 minutes to complete the examination.
4.
The total weight of the examination is 100 points.
5.
There are six (6) multiple choice and three (3) calculation problems. Work five (5) multiple
choice problems and all calculation problems. Show all work; partial credit will be given for correct
work shown.
6.
If you have any questions during the examination, see your instructor who will
be located in the classroom.
7.
Start:
Stop:
11:00 a.m.
11:50 a.m
PROBLEM
POINTS
1-6
25
7
25
8
25
9
25
TOTAL
100
PERCENTAGE
CREDIT
CIRCLE THE SINGLE BEST ANSWER FOR ALL MULTIPLE CHOICE QUESTIONS. IN
MULTIPLE CHOICE QUESTIONS WHICH REQUIRE A CALCULATION SHOW WORK FOR
PARTIAL CREDIT.
1. A loop of wire is moving near a long, straight wire carrying a constant current I as shown
in the figure below.
Determine the direction of the induced current in the loop as it moves away from the wire.
a.
Clockwise.
b.
Counterclockwise.
c.
Into the page.
d.
Out of the page.
(5)
5. A circular coil lies flat on a horizontal table. A bar magnet is held above its center with its
north pole pointing down. The stationary magnet induces (when viewed from above)
a. No current in the coil.
b. A clockwise current in the coil.
(5)
c. A counterclockwise current in the coil.
d. A current whose direction cannot be determined from the information given.
3. If the current in an inductor is doubled, by what factor is the energy stored multiplied?
a. 4.
b. 2.
(5)
c. 1.
d. ½.
4. The figure below shows a top view of a bar that can slide on two frictionless rails.
The magnetic field is directed perpendicularly downward, into the page.
Which of the following statements is correct?
a.
The induced current in the loops is zero.
b.
The induced current in the loop is counterclockwise.
c.
An external force is required to keep the bar moving at a constant velocity.
d.
No force is required to keep the bar moving at a constant velocity.
(5)
PHYS 2212 Exam 3, Version 1
Spring 2012
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5. A student attempts to induce a current in a coil using a bar magnet. As she moves the
magnet toward the coil —
a. `Electrical energy is transformed into mechanical energy.
b. Mechanical energy is transformed into electrical energy.
(5)
c. Gravitational potential energy is transformed into a magnetic field.
d. The electric field is transformed into gravitational potential energy.
6. The “ELI the ICE man” mnemonic helps you remember that
a. Current in an inductor lags behind voltage.
b. Voltage in an inductor lags behind current.
(5)
c. Current in a resistor lags behind voltage.
d. Voltage in a resistor lags behind current.
7. A series RLC circuit contains the following components: R = 100 Ω, L = 0.300 H, C =
1.90 µF, and a source with ΔVMAX = 220 V operating at 40.0 Hz.
(a) Find the inductive reactance in the circuit.
X L  2fL  75.4 
(b) Find the capacitive reactance in the circuit.
X C  1 / 2fC  2094 
(c) Find the impedance in the circuit.
PHYS 2212 Exam 3, Version 1
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Z  R 2  ( X L  X C ) 2  2021 
(d) Calculate the maximum current in the circuit.
I rms 
Vrms
 0.109 A
Z
(e) Determine the phase angle between the current and source voltage.
  tan 1 (
X L  XC
)  87.2o
R
(f) Does current lead voltage in this circuit or lag behind? Explain.
Current leads since the phase angle is negative.
8. A ray of light travels from air into another medium, making an angle of θ1 = 45.0° with
the normal as in the figure below.
a.
Find the angle of refraction θ2 if the second medium is fused quartz. (The index
of refraction for fused quartz is 1.458.)
n1 sin 1  n2 sin 2
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n1 sin 1 / n2  sin 2
 2  29.0o
b. Find the angle of refraction θ2 if the second medium is carbon disulfide. (The
index of refraction for carbon disulfide is 1.628.)
n1 sin 1  n2 sin 2
n1 sin 1 / n2  sin 2
 2  25.7o
9. The figure below shows a top view of a bar that can slide on two frictionless rails.
The resistor is R = 5.10 Ω, and a 3.50-T magnetic field is directed perpendicularly
downward, into the page. Let = 2.20 m.
a. Find the current induced in the bar as it is moved to the right at a constant speed
of 3.60 m/s.
  Bvl  (3.50 T )(3.60 m / s)(2.20 m)  27.7 V
I

R
 5.43 A
PHYS 2212 Exam 3, Version 1
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b. Is the direction of the current in the loop clockwise or counterclockwise?
Counterclockwise
c. Calculate the applied force required to move the bar to the right at a constant
speed of 3.60 m/s.
Fap  FB  IBl sin   (5.43 A)(3.50 T )(2.20 m) sin(90.0o )  41.9 N
PHYS 2212 Exam 3, Version 1
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