PHYS 2 Chapter 29 T/F
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A changing magnetic field can produce an electric current
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True
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A constant magnetic field can be used to produce an electric current
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True
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An emf is induced in a wire by moving the wire near a magnet
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True
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An emf is induced in a wire by keeping a stationary magnet near the wire
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False
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An emf is induced in a wire by changing the current in a nearby wire
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True
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A changing magnetic flux through a closed loop of wire induces an emf in that loop
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False
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A constant magnetic flux through a closed loop of wire induces an emf in that loop
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False
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There is no induced emf in a wire that is moving parallel to the magnetic field if the wire is moving in the direction of the magnetic field
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True
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There is an induced emf in a wire that is moving parallel to the magnetic field if the wire is moving in the opposite direction to that of the magnetic field
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False
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Faradays law of induction and lenzs law are actually the same law stated differently
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False
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According to lenzs law, the direction of the induced current in a conduction loop of wire is that which tends to oppose the change that produces it
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True
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The emf in a conduction rod of lenght L moving perpendicular to the magnetic field is directly proportional to the speed of the rod
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True
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In nuclear power plants, the nuclear energy i used to make steam which is then used to produce electricity
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True
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For the maximum induced emf in the coil of a generator, the term sin(wt) has a value of zero
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False
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For the maximum induced emf in the coil of a generator, the term sin(wt) has a value of one
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True
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The three loops of wire shown in Fig. 29-1 are all subject to the same uniform magnetic field "b" that does not vary with time. Loop 1 oscillates back and forth as the bob in the pendulum, loop 2 rotates above the vertical axis, and loop 3 oscillates up and down at the end of a spring. Which loop, or loops, will have an induced emf?
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Loop 2
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Magnetic flux depends upon
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the magnetic field, the area involved, the orientation of the area with respect to the field (aka all of the above)
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According to lenzs law, the direction of an induced current in a conductor will be that which tends to prodice which of the following effects?
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oppose the effect which produces it
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A rectangular coil lies flat on a horizontal surface. A bar magnet is held above the center of the coil with its north pole pointing down. What is the direction of the induced current in the coil?
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There is no current in the coil
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A circular coil of copper wire is lying flat on a horizontal table. A bar magnet is held with its south pole downward, vertically above the center of the coil. The magnet is released from rest and falls toward the coil. As viewed from above, you can say that, as it falls, the magnet induces
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clockwise current in the loop
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A circular coil of copper wire is lying flat on a horizontal table. A bar magnet is held with its south pole downward, vertically above the center of the coil. The magnet is kept stationary with respect to the coil. As viewed from above, you can say that the magnet induces
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no current in the loop
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A rectangular coil lies flat on a horizontal surface. A bar magnet is held above the center of the coil with its north pole pointing down. If the magnet is dropped from this position what is the direction of the induced current in the coil
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counterclockwise
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A circular loop of wire of area 25cm2 lies in the plane of the paper. An increasing magnetic field "b" is coming out of the paper. What is the direction of the induced current in the loop?
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clockwise
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A circular loop of wire of area 25cm2 lies in the plane of the paper. A decreasing magnetic field "b" is coming out of the paper. What is the direction of the induced current in the loop?
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counterclockwise
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A 200-loop coil of cross sectionl area 8.5cm2 lies in the plane of the paper. Directed out out of the plane of paper is a magnetic field of 0.06T. The field out of the paper decreases to 0.02T in 12 milliseconds. What is the direction of the current induced?
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counterclockwise
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A coil lies flat on a horizontal table top in a region where the magnetic field points straight down. The magnetic field disappears suddenly. When viewed from above, what is the direction of the induced current in this coil as the field disappears?
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clockwise
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The wire in Fig, 29-2 carries a current "I" that is increasing with time at a constant rate. The induced emf in each of the loops is such that
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loop A has a clockwise emf, loop B has no induced emf, and loop C has a counterclockwise emf
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The wire in Fig, 29-2 carries a current "I" that is decreasing with time at a constant rate. The induced emf in each of the loops is such that
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loop A has a counterclockwise emf, loop B has no induced emf, and loop C has a clockwise emf
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A long straight wire lies on a horizontal table and carries an ever-increasing current northward. Two coils of wire lie flat on the table, one on either side of the wire. When viewed from above, the induced current circles
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counterclockwise in the eat coil and clockwise in the west coil
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Fig. 29-3 below shows a bar magnet moving upward along the vertical axis toward a horizontal coil. The poles of the bar magnets are labeled X and Y. As the bar approaches the coil it induced an electric current in the direction indicated on the figure. What are the correct polarities of the magnet?
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X=south, Y=north
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A horizontal rod (orientated in the east-west direction) is moved northward at constant velocity through a magnetic field that points straight down. Make a statement concerning the potential induced across the rod
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the west end of the rod is at higher potential than the east end
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A metallic rod moves at constant speed in the positive x direction inside a uniform magnetic field as shown in Fig, 29-6. Positive and negative charges build up on the rod as indicated. What is the direction of the magnetic field?
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negative z
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An electric generator transforms
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mechanical energy into electrical energy
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A rectangular coil with N turns, length L, and width W, as shown in Fig 29-10, is rotating in a magnetic field B with an angular frequency "w" . If the area of the coil is A, what is the induced emf in the coil?
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All of these answers are correct
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A transformer is a device used to
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increase or decrease an ac voltage
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In a transformer, the power input
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is equal to the power output
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If the number of turns on the secondary coil of a transformer are less than those on the primary, the result is a
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step-down transformer
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Electric power is transmitted over long distances at high voltage because
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there is less power lost
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Electric fields produced by changing magnetic fields
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are nonconservative
