大学物理（下）（College Physics II） 知到智慧树答案2024 z27540

第一章 单元测试

1、 A charge +Q is fixed in position as a small charge +q is brought near it and released from rest. Which best describes the magnitude of the velocity of the charge +q as r, the distance between the charges increases? ( )

A:The magnitude of the velocity will increase, but its rate of increase will decrease.
B:The magnitude of the velocity will remain constant.
C:The magnitude of velocity will increase, but its rate of decrease will increase.
D:The magnitude of the velocity will increase, and its rate of increase will also increase.
E:The magnitude of the velocity will decrease, and its rate of decrease will also decrease.
答案: The magnitude of the velocity will increase, but its rate of increase will decrease.

2、 The motion of large bodies at great distances is governed primarily by gravity and not by the electrostatic force because ( )

A:the majority of matter is electrically neutral
B:the electrostatic force is canceled out by the magnetic force
C:the electrostatic force is felt only over short distances
D:of the relative scarcity of antiparticles
E:gravity is a much stronger force than the electrostatic force
答案: the majority of matter is electrically neutral

3、 An object with a charge of –2q feels a force of F when put at a point P in an electric field. In terms of F and q, the strength of the electric field at this point is ( ).

A:
B:
C:2qF
D:
E:
答案:

4、 All of the following are true about Gauss’ law EXCEPT ( )

A:Gauss’ law is useful when the electric field is perpendicular to the differential area.
B:Gauss’ law refers to the flux through a closed surface.
C:A rectangle is an example of a Gaussian surface.
D:Gauss’ law states that the flux through the closed surface is proportional to the total charge within the surface.
E:Gauss’ law is useful when the electric field is zero.
答案: A rectangle is an example of a Gaussian surface.

5、 Based on Gauss’ Law, which of the following affects the electric flux through a Gaussian surface?( )

A:a charge moving with a constant velocity outside the surface
B:a stationary electric charge outside the surface
C:a magnetic monopole enclosed by the surface
D:a stationary electric charge enclosed by the surface
E:a magnetic dipole outside of the surface
答案: a stationary electric charge enclosed by the surface

6、 Which of the following pairs of charge distributions and Gaussian surfaces are correctly paired such that the Gaussian surface can be used to find the electric field associated with that charge distribution?( )

A:plane and cylinder
B:infinite line and rectangle
C:plane and rectangle
D:plane and sphere
E:infinite line and sphere
答案: plane and cylinder

7、 If the electric field does positive work on a negative charge as the charge undergoes a displacement from point A to point B within an electric field, then the electrical potential energy ( )

A:electric fields cannot do work.
B:decreases.
C:increases.
D:is positive.
E:is negative.
答案: decreases.

8、 The negative derivative of electric potential with respect to radius is equal to （ ）

A:charge
B:electric force
C:electric field
D:capacitance
E:potential energy
答案: electric field

9、 The potential difference due to a finite rod along the x-axis is given by the equation V(x) = C[ln(x + L) – ln(x)], where C and L are constants. What is the electric field due to this rod? （ ）

A:
B:
C:
D:
E:
答案:

10、

Point A is a distance L to the left of a charge Q. Point B is a distance 3L to the left of point A. If the electric field at point A due to charge Q is E, what is the electric field at point B?

A:3E
B:E/3
C:E/16
D:E/9
E:E
答案: E/16

11、

A:
B:
C:
D:
E:
答案:

12、

Two solid spheres, both of radius 5 cm, carry identical total charges of 2 nC. Sphere A is a good conductor. Sphere B is an insulator, and its charge is distributed uniformly throughout its volume. How do the magnitudes of the electric fields they separately create at a radial distance of 6 cm compare?

A:
B:
C:
D:
E:
答案:

13、

A:
B:
C:
D:
E:
答案:

14、

A:
B:
C:
D:
E:
答案:

第二章 单元测试

1、 Two charged conducting spheres are touched together. Charge flows between them until which of the following is the same for both spheres?( )

A:electric field at the surface
B:electric field at the center
C:total energy
D:electric potential
E:total charge
答案: electric potential

2、 An uncharged metal sphere is placed within a uniform electric field. Which of the following is true about the net force and torque on the sphere? （ ）

A:The net force and net torque are both zero.
B:The net force is against the direction of the field, and the net torque is against the direction of the field.
C:The net force is zero and the net torque is in the direction of the field.
D:The net force is in the direction of the field, and the net torque is in the direction of the field.
E:The net force is zero and the net torque is against the direction of the field.
答案: The net force and net torque are both zero.

3、 A solid sphere consists of a metal core, a non-conducting middle shell, and a metal outer shell. If a positive charge is placed on the core, where in the sphere will a net positive charge be found? ( )

A:evenly distributed throughout the two metal regions
B:on the outer surface of the core
C:on the outer surface of the outer shell
D:evenly distributed throughout the core
E:on both the outer surface of the core and the outer surface of the outer shell
答案: on both the outer surface of the core and the outer surface of the outer shell

4、 Two conducting spheres of different radii each carry a charge +Q. Which of the following occurs when the two spheres are touched together? ( )

A:Positive charge flows from the larger sphere to the smaller sphere until the electric field at the surface of each sphere is the same.
B:No charge flows.
C:Positive charge flows from the smaller sphere to the larger sphere until the electric field at the surface of each sphere is the same.
D:Positive charge flows from the larger sphere to the smaller sphere until the electric potential at the surface of each sphere is the same.
E:Positive charge flows from the smaller sphere to the larger sphere until the electric potential at the surface of each sphere is the same.
答案: Positive charge flows from the smaller sphere to the larger sphere until the electric potential at the surface of each sphere is the same.

5、 Three identical metal spheres are mounted on insulating stands. Initially, sphere A has a net charge of q and spheres B and C are uncharged. Sphere A is touched to sphere B and removed. Then sphere A is touched to sphere C and removed. What is the final charge on sphere A? ( )

A:q
B:q/6
C:q/3
D:q/4
E:q/2
答案: q/4

6、 A parallel-plate capacitor has capacitance C. A second parallel-plate capacitor has plates with twice the area and half the separation. The capacitance of this second capacitor is most nearly （ ）

A:C/4
B:C/2
C:C
D:4C
E:2C
答案: 4C

7、 All of the following are true about spherical capacitors EXCEPT ( )

A:The electric field outside the outer sphere is zero
B:The electric field between the two spheres is determined only by the charge on the outer sphere
C:The potential difference between the two spheres is the negative integral of the electric field
D:The electric field points radially towards the center of the spheres
E:The capacitance is equal to the charge divided by the potential difference
答案: The electric field between the two spheres is determined only by the charge on the outer sphere

8、 A battery is attached to several different capacitors connected in parallel. Which of the following statements is true?（ ）

A:The potential differences across the capacitors are the same only if the capacitances are the same.
B:The capacitor with the smallest capacitance carries the largest charge.
C:The potential difference across each capacitor is the same, and the equivalent capacitance is greater than any of the capacitors in the group.
D:All capacitors have the same charge, and the equivalent capacitance is greater than the capacitance of any of the capacitors in the group.
E:The capacitor with the largest capacitance carries the smallest charge.
答案: The potential difference across each capacitor is the same, and the equivalent capacitance is greater than any of the capacitors in the group.

9、 A parallel-plate capacitor is connected to a battery. What happens to the stored energy if the plate separation is doubled while the capacitor remains connected to the battery?（ ）

A:It increases by a factor of 4.
第三章
B:It remains the same.
C:It is doubled.
D:It decreases by a factor of 4.
E:It decreases by a factor of 2.
答案: It decreases by a factor of 2.

10、

A:0.03 J
B:0.06 J
C:18 J
D:0.0036 J
E:9 J
答案: 18 J

第三章 单元测试

1、 A particle with electric charge is fired into a region of space where the electric field is zero. It moves in a straight line. Can you conclude that the magnetic field in that region is zero?( )

A:No; an observation of an object with electric charge gives no information about a magnetic field.
B:Yes, you can.
C:No; the field might be parallel to the particle’s velocity.
D:No; the field might be perpendicular to the particle’s velocity.
E:No; the particle might need to have charge of the opposite sign to have a force exerted on it.
答案: No; the field might be parallel to the particle’s velocity.

2、 Which of the following explains why a magnetic field does no work on a moving charged particle?( )

A:The magnetic force depends on the direction of motion of the particle.
B:The magnetic force is always perpendicular to the direction of motion.
C:There is always an electric field that cancels the work done by the magnetic field.
D:The magnetic force depends on the speed of the particle.
E:The magnetic force is conservative.
答案: The magnetic force is always perpendicular to the direction of motion.

3、 Two long parallel wires are fixed at a distance d apart and each carry a current of I. The force of attraction between them is F. If the distance between the wires is doubled and the current in each of the wires is doubled, what is the new force of attraction between the wires? ( )

A:F/4
B:2F
C:F
D:F/2
E:4F
答案: 2F

4、 The Biot-Savart Law is used to（ ）

A:determine the electric field created by an electric current
B:determine the force field created by an electric current
C:determine the magnetic field created by an electric current
D:determine the magnetic field created by individual point charges
E:determine the electric field created by individual point charges
答案: determine the magnetic field created by an electric current

5、 If two current carrying wires exert a force of 50 N on each other, what force will they feel if the distance between them is halved?( )

A:50 N
B:100 N
C:200 N
D:12.5 N
E:25 N
答案: 100 N

6、 Which of the following is not used when applying Ampere’s law?( )

A:magnetic field
B:a line integral
C:a dot product
D:a surface integral
E:a length differential
答案: a surface integral

7、 An infinitely large current-carrying sheet lies on the xy-plane carrying current in the y-direction. Which of the following is false about the magnetic field that it creates?( )

A:The magnetic field can be calculated using Ampere’s law.
B:The magnetic field depends on the distance away from the plane.
C:The magnetic field is in the positive x-direction.
D:The magnetic field depends on the current density in the sheet.
答案: The magnetic field depends on the distance away from the plane.

8、

A:
B:
C:
D:
E:
答案:

9、

A:0.3125V
B:0.02V
C:3.125V
D:0.002V
答案: 0.002V

10、

There is a clockwise current in a circular loop of wire in an external magnetic field directed out of the page as shown in the diagram. The effect of the magnetic field is to make the loop

A:move into the page
B:rotate perpendicularly to the page.
C:expand.
D:contract.
E:rotate in the plane of the page.
答案: contract.

11、

What is the magnetic field at point P due to the segment of wire AB carrying current I? 

A:
B:
C:
D:
E:
答案:

12、

A:g + lB
B:(BI – l/2) + mg

C:mg – IB/2
D:mg + IBl
E:mg – IBl
答案: mg – IBl

第四章 单元测试

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:they all move to the left side of the loop
B:clockwise
C:they are stationary
D:they all move to the right side of the loop
E:counterclockwise
答案: clockwise

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:No change will occur in the loop
B:The loop will rotate about a diameter.
C:There is an induced current in the loop that is counterclockwise in direction.
D:There is an induced current in the loop that is clockwise in direction.
E:The loop will rotate about an axis perpendicular to the plane of the page.
答案: There is an induced current in the loop that is clockwise in direction.

3、 Lenz’s Law indicates which of the following?( )

A:The induced EMF produces a magnetic field that opposes the change that produced the EM
B:Light incident on a concave mirror produces a virtual image.
C:The force exerted by a magnetic field is perpendicular to both the motion of the charged particle and the direction of the magnetic field.
D:The induced EMF is equal to the change in magnetic flux.
E:There are no magnetic monopoles.
F:
答案: The induced EMF produces a magnetic field that opposes the change that produced the EM

4、 If the magnetic field B through a loop of wire is decreasing, the induced magnetic field will be ( )

A:perpendicular to B
B:in the opposite direction of B
C:at an acute angle to B
D:there is no induced magnetic field
E:in the same direction as B
答案: in the same direction as B

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:twice as large
B:half as large
C:unchanged
D:four times as large
E:one-fourth as large
答案: unchanged

6、 Which of the following circuit element stores energy in the electromagnetic field? ( )

A:Variable resistor
B:Inductor
C:Condenser
D:Resistance
答案: 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:45 V
B:70.7 V
C:94.2 V
D:141 V
E:22.5 V
答案: 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:0.046 V
B:0.023 V
C:0.092 V
D:0.012 V
E:0 V
答案: 0.046 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:Along the y-axis with constant velocity
B:Along the z-axis with constant velocity
C:Rotate the loop about the z-axis
D:Along the x-axis with increasing velocity
E:Current cannot be induced in the loop because the magnetic field is uniform
答案: Along the x-axis with increasing 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:1.2 V
B:0.48 V
C:0.12 V
D:4.8 V
E:2.4 V
答案: 0.48 V

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