PES 1120 General Physics II
Practice Exam 4
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One (3” x 5”) index card may be used for formulas or other notes or diagrams.
Definitions & Concepts (2 pts each)
1. Which of the units below are equivalent to Henrys times Farads?
a. Ohm
b. Hertz
c. Seconds2
d. Ampere
2. A simple circuit has an AC source and a capacitor. As the voltage cycles through the circuit
from the source, which is true of the current for every cycle?
a. The current maximum occurs before the voltage maximum occurs.
b. The current maximum occurs at the same time as the voltage maximum occurs.
c. The current maximum occurs after the voltage maximum occurs.
3. This material exhibits a magnetic field only in the presence of an external magnetic field, and it
is aligned with the external field.
a. Ferro-magnetic
b. Paramagnetic
c. Diamagnetic
Applications (4-6 pts each)
4. A solenoid is to be made from a long tightly-wrapped coil of wire. The solenoid will have a
diameter of 2 cm, with a wrapping density of 20 coils per cm. How long must the solenoid be
to achieve an inductance of 2 mH? How much magnetic energy is stored in the solenoid when
2 A of current is passing through it? What voltage does the solenoid produce when the current
is changed from 2 A to zero in 0.2 seconds?
5. A coil is wrapped with 300 turns of wire on the perimeter of a square frame (side length = 20
cm). Each turn has the same area as the frame, and the total resistance of the coil is 1.5 . A
uniform magnetic field perpendicular to the plane of the coil, changes in magnitude at a
constant rate from 0.50 T to 0.90 T in 2.0 s. What is the magnitude of the induced current in
the coil while the field is changing?
6. A rectangular loop (area = 0.15 m2) turns in a uniform magnetic field with B = 0.20 T at an
angular rate of 0.6 rad/s. At an instant when the angle between the magnetic field and the
normal to the plane of the loop is /2 rad, what is the magnitude of the emf induced in the
loop?
R. Gist
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Long Semester Ver. A, Rev 1
PES 1120 General Physics II
Practice Exam 4
7. In the arrangement shown, a conducting bar of
negligible resistance slides along horizontal,
parallel, frictionless conducting rails connected
as shown to a 2.0- resistor. A uniform 1.5-T
magnetic field is perpendicular to the plane of
the paper. If length = 60 cm, what is the
current through the resistor at the instant the
speed of the bar is equal to 4.2 m/s?
8. A DC circuit contains a 10 Ω resistor and a 1 mH inductor connected in series with a 12-V
battery. What is the steady state current through this circuit? How long after the circuit is
interrupted does the current reach half of this value?
9. An AC voltage of the form E(t) = 140 sin(500*t) volts is supplied to a series
RLC circuit, with R = 1 kΩ, L = 1 H, and C = 1 μF. The driving frequency is
500 rad/s, but find the natural (or resonance) frequency of this circuit,
the impedence of the circuit, and the maximum voltage across the
resistor and the capacitor.
10. What is the ratio of primary turns to secondary turns in a step-down transformer that steps
down a voltage of 120-V to 10-V? If the current in the secondary loop is 0.1 ampere, what was
the supplied current (assuming 100% efficiency in the transformer)?
Permittivity of free space
Permeability of free space
Speed of light in vacuum
R. Gist
Constants
o=8.854 x 10-12 C2/(N·m2)
o=4 x 10-7 T·m/A
c=2.98 x 108 m/s
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Powers of Ten
kilo- (k)
milli- (m)
micro- ()
nano- (n)
pico- (p)
103
10-3
10-6
10-9
10-12
Long Semester Ver. A, Rev 1