第四章测试1.The magnetic field from a loop of current carrying wire in the plane of the page is directed out of the page. In which direction do the electrons in the wire loop move?( )
A:counterclockwise
B:they all move to the left side of the loop
C:they all move to the right side of the loop
D:they are stationary
E:clockwise
答案:E
2.A magnetic field that is increasing with time is directed out of the page and passes through a circular loop of wire in the plane of the page. Which of the following is true?( )
A:There is an induced current in the loop that is counterclockwise in direction.
B:There is an induced current in the loop that is clockwise in direction.
C:The loop will rotate about an axis perpendicular to the plane of the page.
D:No change will occur in the loop
E:The loop will rotate about a diameter.
3.Lenz's Law indicates which of the following?( )
A:The force exerted by a magnetic field is perpendicular to both the motion of the charged particle and the direction of the magnetic field.
B:The induced EMF is equal to the change in magnetic flux.
C:Light incident on a concave mirror produces a virtual image.
D:The induced EMF produces a magnetic field that opposes the change that produced the EM E:
F:There are no magnetic monopoles.
4.If the magnetic field B through a loop of wire is decreasing, the induced magnetic field will be ( )
A:in the same direction as B
B:perpendicular to B
C:at an acute angle to B
D:in the opposite direction of B
E:there is no induced magnetic field
5.A long, fine wire is wound into a coil with inductance 5 mH. The coil is connected across the terminals of a battery, and the current is measured a few seconds after the connection is made. The wire is unwound and wound again into a different coil with L = 10 mH. This second coil is connected across the same battery, and the current is measured in the same way. Compared with the current in the first coil, is the current in the second coil ( )
A:half as large
B:four times as large
C:one-fourth as large
D:unchanged
E:twice as large
6.Which of the following circuit element stores energy in the electromagnetic field? ( )
A:Resistance
B:Variable resistor
C:Condenser
D:Inductor
7.A straight rod of length 3.0 m is held perpendicular to a magnetic field of 2.0 T. It is rotated about its midpoint at a rate of 5.0 revolutions per second, remaining perpendicular to the field the entire time. The emf generated in the rod is most nearly ( )
A:22.5 V
B:70.7 V
C:45 V
D:94.2 V
E:141 V
8.
A circular loop of wire with a radius of 5 cm rotates clockwise at a constant angular velocity through a magnetic field B = 5 T. The plane of the loop goes from being perpendicular to the field to being at a 45º angle with the field in 0.25 s. The average emf induced in the loop will be
A:0.012 V B:0.092 V C:0.023 V D:0.046 V E:0 V 9.
The diagram shows a wire loop in a uniform magnetic field B that points out of the page. In which way should the loop be moved to induce a current within the loop?
A:Rotate the loop about the z-axis B:Current cannot be induced in the loop because the magnetic field is uniform C:Along the y-axis with constant velocity D:Along the x-axis with increasing velocity E:Along the z-axis with constant velocity 10.
In the diagram below, a segment of wire, RS, which is 0.20 m in length, is free to slide along a U-shaped wire located in a uniform 0.60-T magnetic field directed into the page. If wire segment RS is slid to the right at a constant speed of 4.0 meters per second, the potential difference induced across the ends of the wire segment is
A:2.4 V B:1.2 V C:0.48 V D:4.8 V E:0.12 V
