Physics 1202 Practice Quiz 4
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Multiple Choice
MC1:Electromagnetic waves that have a wavelength of 300 m in free space have a frequency of
A) 1 ◊ 10–3 Hz
B) 5 ◊ 105 Hz
*C) 1 ◊ 106 Hz
D) 9 ◊ 106 Hz
E) 1 ◊ 1011 Hz
MC2: Arrange the following types of electromagnetic radiation in order of increasing wavelength: gamma rays, infrared
light, ultraviolet light, visible light.
A) Gamma rays are not electromagnetic radiation.
B) gamma rays, infrared, visible, ultraviolet
*C) gamma rays, ultraviolet, visible, infrared
D) visible, ultraviolet, infrared, gamma rays
E) ultraviolet, visible, infrared, gamma rays
MC3:A 60-W light bulb emits spherical electromagnetic waves uniformly in all directions. If 50% of the power input
to such a light bulb is emitted as electromagnetic radiation, what is the radiation intensity at a distance of 2.00 m
from the light bulb?
A) 15 W/m2
B) 4.8W/m2
C) 2.4W/m2
*D) 0.60W/m2
E) 1.2W/m2
MC4: Which of the following functions satisfy the one-dimensional wave equation?
A) y(x, t) = y0 cos(kx–Êt)
B) y(x, t) = y0 sin(kx–Êt)
C) y(x, t) = y0 sin(kx–Êt) + Bcos(kx–Êt)
D) y(x, t) = y0 (sinkx) · B(cosÊt)
*E) All of these functions satisfy the one-dimensional wave equation.
MC5:Suppose you double the magnetic field in a given region and quadruple the area through which this magnetic
field exists. The effect on the flux through this area would be to
A) leave it unchanged.
B) double it.
C) quadruple it.
D) increase it by a factor of six.
*E) increase it by a factor of eight.
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Problem 1:A particle that has a charge q and a mass m moves with angular velocity w in a circular path of radius
r. (a) Show that the average current created by this moving particle is wq/(2p) and that the magnetic moment of
its orbit has a magnitude of . (b) Show that the angular momentum of this particle has the magnitude of mr2w and
that the magnetic moment and angular momentum vectors are related by , where is the angular momentum about the
center of the circle.
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Problem 2: The figure belowe shows a schematic drawing of an ac generator. The basic generator consists of a
rectangular loop of dimension a x b and has N turns connected to slip rings. The loop rotates (driven by a gasoline
engine) at an angular speed w in a uniform magnetic field .
(a) Show that the induced potential difference between the two slip rings is given by e = NBabw sin wt.
(b) If a = 2.00 cm, b = 4.00 cm, N = 250, and B = 0.200 T, at what angular frequency w must the coil rotate to
generate an emf whose maximum value is 100V?
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