Download Practice Midterm #2

Physics 21
Practice Midterm #2 Problems
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Chapter 19
c 1.
The force on a charged particle created by its motion in a magnetic field is maximum at what angle between the
particle velocity and field?
a. zero
b. 180
c. 90
d. 45
b 2. A proton moves across the Earth’s equator in a northeasterly direction. At this point the Earth’s magnetic field has a
direction due north and is parallel to the surface. What is the direction of the force acting on the proton at this instant?
a. toward the northwest
b. out of the Earth’s surface
c. into the Earth’s surface
d. toward the northeast
c 3. If a proton is released at the equator and falls toward the Earth under the influence of gravity, the magnetic force on
the proton will be toward the:
a. north.
b. south.
c. east.
d. west.
b 4. A horizontal wire of length 3.0 m carries a current of 6.0 A and is oriented so that the current direction is 50 S of W.
The Earth's magnetic field is due north at this point and has a strength of 0.14  104 T. What is the direction of the
force on the wire?
a. out of the Earth’s surface
b. toward the Earth’s surface
c. due east
d. 40 S of E
c 5. A proton is released such that it has an initial speed of 4.0  105 m/s from left to right across the page. A magnetic
field of 1.2 T is present at an angle of 30 to the horizontal direction (or positive x axis). What is the magnitude of the
force experienced by the proton? (qp = 1.6  1019 C)
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a. 4.8  1025 N
b. 1.3  1019 N
c. 3.8  1014 N
d. 7.5  103 N
c 6. A copper wire of length 25 cm is in a magnetic field of 0.20 T. If it has a mass of 10 g, what is the minimum current
through the wire that would cause a magnetic force equal to its weight?
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a. 1.3 A
b. 1.5 A
c. 2.0 A
d. 4.9 A
b 7. A proton moving with a speed of 3.0  105 m/s perpendicular to a uniform magnetic field of 0.20 T will follow which
of the paths described below? (qp = 1.6  1019 C and mp = 1.67  1027 kg)
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a. a straight line path
b. a circular path of 1.6 cm radius
c. a circular path of 3.1 cm radius
d. a circular path of 0.78 cm radius
c 8. A 100-m-long wire carrying a current of 4.0 A will be accompanied by a magnetic field of what strength at a distance
of 0.050 m from the wire? (magnetic permeability in empty space µ0 = 4  107 Tm/A)
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a. 4.0  105 T
b. 2.0  105 T
c. 1.6  105 T
d. zero
Chapter 20
c 9. A metal rod is falling toward the surface of the Earth near the equator. As it falls, one end of the rod becomes
positively charged due to the motional emf of the rod through the Earth's magnetic field. The rod is oriented so that:
a. the rod is vertical with the positive end higher.
b. the rod is horizontal with the positive end toward the north.
c. the rod is horizontal with the positive end toward the east.
d. the rod is horizontal with the positive end toward the west.
b 10. Two loops of wire are arranged so that a changing current in one will induce a current in the other. If the current
in the first is increasing clockwise by 1.0 A every second, the induced current in the second loop will:
a. be increasing counterclockwise.
b. stay constant.
c. increase clockwise also.
d. stay zero.
a 11.
The basic function of the electric generator is which of the following conversion processes?
a. mechanical energy to electrical
b. electrical energy to mechanical
c. low voltage to high or vice versa
d. alternating current to direct
b 12.
The function of the electric motor is which one of the following conversion processes?
a. mechanical energy to electrical
b. electrical energy to mechanical
c. low voltage to high or vice versa
d. alternating current to direct
c 13. A uniform 4.5-T magnetic field passes through the plane of a wire loop 0.10 m2 in area. What flux passes through
the loop when the direction of the 4.5-T field is at a 30 angle to the normal of the loop plane?
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a. 5.0 Tm2
b. 0.52 Tm2
c. 0.39 Tm2
d. 0.225 Tm2
b 14. A coil is placed in a magnetic field and has a flux B through it. The coil is stressed so that its area reduces to
75% of its original value. If the plane of the coil stays the same and the flux through it remains the same, how must
the magnetic field change?
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a. It must increase by 25%.
b. It must increase by 33%.
c. It must increase by 125%.
d. It must decrease by 25%.
c 15. A flat coil of wire consisting of 20 turns, each with an area of 50 cm2, is positioned perpendicularly to a uniform
magnetic field that increases its magnitude at a constant rate from 2.0 T to 6.0 T in 2.0 s. If the coil has a total
resistance of 0.40 , what is the magnitude of the induced current?
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a. 70 mA
b. 140 mA
c. 500 mA
d. 800 mA
c 16. A large jetliner with a wingspan of 40 m flies horizontally and due north at a speed of 300 m/s in a region where
the magnetic field of the earth is 60 µT directed 50 below the horizontal. What is the magnitude of the induced emf
between the ends of the wing?
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a. 250 mV
b. 350 mV
c. 550 mV
d. 750 mV
Chapter 21
a 17.
In an AC series circuit, the current in a pure resistor differs in phase with the applied voltage by what angle?
a. zero
b. 45
c. 90
d. 180
b 18.
In a capacitor in an AC circuit, the voltage:
a. leads the current by 90°.
b. lags the current by 90°.
c. may lead or lag the current depending on the frequency.
d. is in phase with 70.7% of the current.
d 19. In an AC series circuit, the voltage in the inductor differs in phase with the voltage in the capacitor by what
angle?
a. zero
b. 45
c. 90
d. 180
a 20. The current in an inductor connected to an AC voltage source lags the voltage. This lag is caused by the:
a. back emf in the coil.
b. voltage across the coil.
c. time required for electrical signals to travel through all the coils of an inductance.
d. resistance of the coil.
d 21. What is the impedance of an AC series circuit that is constructed of a 10.0- resistor along with 12.0  inductive
reactance and 7.0  capacitive reactance?
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a. 37.0 
b. 27.7 
c. 27.1 
d. 11.2 
d 22. Consider an AC series circuit containing a coil, capacitor and resistance. Tripling the frequency will change the
inductive reactance by what factor?
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a. 1/3
b. 1.0
c. 1.73
d. 3.0
d 23. An FM radio tuning circuit has a coil with an inductance of 0.003 0 mH. What is the value of the capacitance if
the set is tuned to 98 MHz?
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a. 1.8  106 F
b. 12  106 F
c. 0.98  106 F
d. 0.88  106 F
c 24. A transformer consists of a 500-turn primary coil and a 2 000-turn secondary coil. If the current in the secondary
is 3.00 A, what is the primary current?
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a. 0.750 A
b. 1.33 A
c. 12.0 A
d. 48.0 A
Chapter 22
c 25. The wave-particle duality of light means that, in the same experiment:
a. light will act both like a wave and like a particle.
b. light will act either like a wave or like a particle.
c. light will not act like either a wave or a particle.
d. light always exists as two waves or as two particles.
b 26. When viewing your image in a hand-held mirror, if you move the mirror away at a speed v, the image appears to:
a. also move away at v.
b. move away at 2v.
c. move away at v/2.
d. not move.
b 27.
As a monochromatic light ray is transmitted through an air-to-glass boundary, what happens to the wavelength?
a. increases
b. decreases
c. remains unchanged
d. approaches zero value
a 28. Which of the following describes what will happen to a light ray incident on a glass-to-air boundary at greater
than the critical angle?
a. total reflection
b. total transmission
c. partial reflection, partial transmission
d. partial reflection, total transmission
b 29.
Water has an index of refraction of 1.333. What is the speed of light through it? (c = 3.00  108 m/s)
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a. 4.00  108 m/s
b. 2.25  108 m/s
c. 4.46  108 m/s
d. 1.46  108 m/s
d 30. A light ray in air is incident on an air-to-glass boundary at an angle of 30.0º and is refracted in the glass at an
angle of 21.0º with the normal. Find the index of refraction of the glass.
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a. 2.13
b. 1.74
c. 1.23
d. 1.40
c 31. What is the angle of incidence on an air-to-glass boundary if the angle of refraction in the glass (n = 1.52) is 25º?
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a. 16º
b. 25º
c. 40º
d. 43º
b 32. A container of flint glass (n = 1.66) holds a small quantity of benzene (n = 1.501). What is the critical angle for
internal reflection of a ray in the glass when it is incident on the glass-to-liquid surface?
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a. 89.5º
b. 64.7º
c. 41.1º
d. 37.0º