浙江大学大学物理甲下 midtese

Answer: B
Pm B
9. A cylindrical region of radius R=3.0cm contains a uniform magnetic field parallel to its axis. If the field is changing at the rate 0.60T/s, the electric field induced at a point R/2 from the cylinder axis is: A. 0 B. 0.0045V/m C. 0.0090V/m D. 0.028V/m E. None of these
Answer: D
E E0 E E0
E
e
4. Each of the three 25μF capacitors shown is initially uncharged. How many coulombs of charge pass through the ammeter A after the switch S is closed? A. 0.10 B. 0.30 C. 10 D. 0.033 E. None of these .
Answer: B
7. The diagram shows a straight wire carrying current i in a uniform magnetic field. The magnetic force on the wire is indicated by an arrow but the magnetic field is not shown. Of the following possibilities, the direction of the magnetic field is: A. to the right B. opposite the direction of F C. in the direction of F D. into the page E. out of the page
B dA 0
E ds dΦB /dt
B ds 0i 0 0dΦE /dt
B. C.
D.
Answer: D
13. Which diagram below illustrates the path of a light ray as it travels from a given point X in air to another given point Y in glass?
Answer: C
U wSd
6. The current is from left to right in the conductor shown. The magnetic field is out of the page and point S is at a higher potential than point T. The charge carriers are: A. positive B. negative C. neutral D. absent E. moving near the speed of light
Answer: E
F idl B
8. The magnetic torque exerted on a flat current-carrying loop of wire by a uniform magnetic field B is : A. Maximum when the plate of the loop is perpendicular to B B. Maximum when the plate of the loop is parallel to B C. Dependent on the shape of the loop for a fixed loop area D. Independent of the orientation of the loop E. Such as to rotate the loop around the magmetic field lines
Answer: B
B 2 E 2r r t
10. Of the three chief kind of magnetic materials (diamagnetic, paramagnetic, and ferromagnetic), which are used to make permanent magnets? A. Only diamagnetic B. Only ferromagnetic C. Only paramagnetic D. Only paramagnetic and ferromagnetic
2. Solution:
(1)The energy density is e 1 e2 2 E , u 0E 2 4 0 r 2 32 2 0 r 4
U udV
R
e2 32 2 0 r 4
R
4r 2dr
e2 8 0 R
(2)
2U 2 e 2 e2 e2 udV 4r 2 dr R0 32 2 r 4 3 3 8 0 R R0 0 8 0 R0
Answer: E
14. light traveling through three transparent substances follows the path shown in Fig. Arrange the indices of refraction in order from smallest to largest. Note that total internal reflection does occur in the bottum surface of the medium 2. A. n1< n2< n3 B. n2< n1< n3 C. n1< n3< n2 D. n3< n1< n2 E. none of these
Answer to the final examination
Ⅰ. multiple-choice
1. B 2. E 3. D 4. B 5.C 6. B 7. E 8. B 9. B 10. B 11. E 12.D 13. E 14.D
1. Two conducting spheres are far apart. The smaller sphere carries a total charge of 6 10-8C. The larger sphere has a radius that is twice that of the smaller and is neutral. After the two sphere are connected by a conducting wire, the charges on the smaller and larger spheres, respectively, are: A. 4 10-8C and 2 10-8C. B. 2 10-8C and 4 10-8C. C. -6 10-8C and 12 10-8C. D. 6 10-8C and 0. E. 3 10-8C and 3 10-8C.
( L2 y 2 y )
V k y (2) E y (1 ) y 4 0 L2 y 2 (3) 2 k 4 0 ( L y y)
2 2
k 4 0
L,
L L y y 2
2 2
L2 3 2 2 2 L y Ly y , y L 4 4
Answer: E
Q2 Q2 U , UC , 2C 8C Q 2 Q 2 3Q 2 3 Q 2 3 UL U 2C 8C 8C 4 2C 4
12. Which of the following equations, along with a symmetry argumant, can be used to calculate the magnetic field between the plates of a charged parallel plated capacitor with circular plates?:A q / 0 Ed A.
Answer: D
Total reflaction
Ⅱ. calculation
1. Solution:
(1) dV V
L
1 4 0
dx
x y
2 2
k
1 4 0
2
kxdx x2 y2
2 L 0
1 4 0
kxdx x2 y2
0

4 0
x y

k 4 0
3 R0 R 2
(3)
e2 mec 2 , R 1.401015 m 8 0 R 8 0 mec 2 e2
r 2 r 3. r R : B 2r 0i 2 , B 0i R 2R 2 0i r 1 0i R Bmax , 0i , r 2 2R 2R 2 2R 2 0i r R : B 2r 0i, B , 2r 0i 0i 0i 1 0i Bmax , Bmax , , r 2R 2R 2R 2r 2 2R
Answer: B
11. In an oscillating LC circuit the total stored energy is U and the maximum charge on the capacitor is Q. When the charge on the capacitor is Q/2, the energy in the inductor is: A. U/2 B. U/4 C. (4/3)U D. 3U/2 E. 3U/4
Answer: B
4 0 r1
q1

4 0 r2
q2
2. If the electric field is in the positive x direction and has a magnitude given by E=Cx, where C is a constant, then the electric potential is given by V= A. C B. -C C. Cx D.(1/2)Cx2 E. -(1/2)Cx2
Answer: E
来自百度文库
V E x
3. When an external electric field is applied to an insulator with dielectric constant κ, the magnitude of the electric field produced in the insulator by the polarization charge is propotional to A. κ. B. 1/κ. C. κ-1. D. 1-1/κ. E. 1+1/κ.
Answer: B
Q CV (C1 C2 C3 )V
5. A battery is used to charge a parallel-plate capacitors, after which it is disconnected. Then the plates are pulled apart to twice their original separation. This process will double the: A. capacitance. B. surface charge density on each plate. C. stored energy. D. electric field between the two plates. E. charge on each plate.