PES 112 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.
DC circuit summary and AC circuit summary sheets will be provided
Definitions & Concepts (2 pts each)
1. Which of the units below are equivalent to one Henry per second?
a. Ohm
b. Watt
c. Volt
d. Ampere
Applications (4-6 pts each)
2. 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?
3. 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?
4. A high-voltage power line operates at 500,000 V-rms and carries an rms current of 500 A. If
the resistance of the cable is 0.05Ω/km, what is the resistive power loss in 200 km of the power
line?
5. 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. Find
the natural (or resonance) frequency of this circuit, the impedence of
the circuit, and the maximum voltage across the resistor and the
capacitor.
1 kΩ
1Η
= 140 sin (500 t)
1 μF
R. Gist
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Long Semester Ver. B, Rev 1
PES 112 General Physics II
Practice Exam 4
6. A British AC source provides a 230-V rms emf at a frequency of 50-Hz to a parallel RLC
circuit, with R = 200 Ω, L = 1 H, and C = 15 µF. Find the maximum voltage, the angular
frequency of the source, and the phase angle between the source voltage and the current
through the circuit.
7. What is the ratio of primary turns to secondary turns in a step-down transformer that converts
120-V power 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)?
8. A laser of green light with a wavelength of 540 nm has an average power of 1.5 mW. What is
the frequency of this EM-wave in free space? If the maximum electric field component of the
electromagnetic wave is measured at 600 V/m, what is the maximum magnetic field
component? If the beam is focused on a spot with a diameter of 1.0 mm, find the intensity of
the beam and the radiation pressure.
Permittivity of free space
Permeability of free space
R. Gist
Constants
εo=8.854 x 10-12 C2/(N·m2)
μo=4π x 10-7 T·m/A
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Powers of Ten
milli- (m)
micro- (μ)
nano- (n)
pico- (p)
10-3
10-6
10-9
10-12
Long Semester Ver. B, Rev 1