Physics test 1

10. What is the atomic number of an atom? a. it is the number of protons in the atom b. total number of protons and neutrons c. total number of electrons, protons, and neutrons d. total charge of nucleus e. total charge of atom f. total charge of electrons

answer a

15. Experimenter A uses a test charge q and experimenter B uses a test charge 2q to measure an electric field produced by stationary charges. A finds a field that is: a. the same as the field found by B b. greater than the field found by B c. less than the field found by B d. either greater or less than the field found by B, depending on the masses of the test charges e. either greater or less than the field found by B, depending on the accelerations of the test charges

answer a

16. Two thin spherical shells, one with radius R and the other with radius 2R, surround an isolated charge point particle. The ratio of the number of field lines through the larger sphere to the number through the smaller is: a. 1 b. 2 c. 4 d. 1/2 e. 1/4

answer a

2. In the figure, a central particle of charge -q is surrounded by two circular rings of charged particles. What are the magnitude and direction of the net electrostatic force on the central particle due to the other particles? a. upward (2k(q^2))/(r^2) b. leftward (10k(q^2))/(r^2) - (16k(q^2))/(R^2) c. downward (10k(q^2))/(r^2)

answer a

24. An electric dipole is oriented parallel to a uniform electric field, as shown. It is rotated to one of the five orientations shown below. Rank the final orientations according to the change in the potential energy of the dipole-filed system, most negative to most positive. a. 1, 2, 3, 4 b. 4, 3, 2, 1 c. 1, 2, 4, 3 d. 3, then 2 and 4 tie, then 1 e. 1, then 2 and 4 tie, then 3

answer a

30. A closed cylinder with a 0.15m radius ends is in a uniform electric field of 300 N/C, perpendicular to the ends. The total flux through the cylinder is: a. 0 b. 4.2 c. 21 d. 280 e. can't tell w/o knowing the areas of the sides and bottom

answer a

4. If a negatively charge plastic rod is brought near one end of a neutral copper rod, what happens to that near end? a. becomes positively charged b. remains neutral c. becomes negatively charged

answer a

6. If an electrically neutral conductor loses electrons, what happens? a. It becomes positively charged b. It remains neutral c. It becomes negatively charged

answer a

1. The figure shows four situations in which five charged particles are evenly spaced along an axis. The charge values are indicated except for the central particle, which has the same charge in all four situations. Rank the situations according to the magnitude of the net electrostatic force on the central particle, greatest first. a. 3 > 2 > 1 > 4 b. 3 > 1 > 2 > 4 c. 2 > 3 = 4 > 1 d. 1 = 2 > 3 = 4

answer b

13. If a positive test charge is placed in an electric field, what is the direction of the force on the test charge? a. opposite the direction of the field vector b. in the direction of the field vector c. perpendicular to the field vector

answer b

17. Choose the correct statement concerning electric field lines: a. field lines may cross b. field lines are close together where the field is large c. field lines point away from negatively charged particle d. a point charge particle released from rest moves along a field line e. none of these are correct

answer b

23. The diagrams below depict four different charge distributions. The charged particles are all the same distance from the origin. The electric field at the origin: a. is greatest for situation 3 b. is zero for situation 4 c. is downward for situation 1 d. is downward for situation 3 e. is least for situation 1

answer b

33. A particle with charge 5.0 uC is placed at the corner of a cube. The total electric flux through all sides of the cube is: a. 0 b. 7.1E4 c. 9.4E4 d. 1.4E5 e. 5.6E5

answer b

5. If a negatively charged conductor is connected to ground, what happens to the conductor? a. becomes positively charged b. becomes neutral c. remains negatively charged

answer b

7. If we monitor a point on a wire where there is a current for a certain time interval, which gives the charge that moves through the point in that interval? a. The ratio of the time interval to the current b. The product of the current and the time interval c. The ratio of the current to the time interval

answer b

8. A charged particle experiences two electrostatic forces (due to other, nearby charged particles). The force vectors are perpendicular to each other. How can you find the magnitude of the net force? a. subtract the two magnitudes b. use the Pythagorean theorem c. add the two magnitudes

answer b

9. Which of these particles has the smallest amount of negative charge? a. neutron b. electron c. proton

answer b

12. In defining an electric field, a test charge is used. Is the test charge positively or negatively charged? Which describes the direction of the electric field vector? a. negatively charged. the field vector is in the same direction as the force on the test charge b. negatively charged. the field vector is in the opposite direction as the force on the test charge c. positively charged. the field vector is in the same direction as the force on the test charge d. positively charged. the field vector is in the opposite direction as the force on the test charge

answer c

18. The diagram shows the electric field lines due to two charged parallel metal plates. We conclude that: a. a proton at X experiences less force than if it were placed at z b. the upper plate is positive and the lower plate is negative c. a proton at X would experience the same force if it were placed at Y d. an electron at X could have its weight balanced by the electrical force e. a proton at X experiences a greater force than if it were placed at Z

answer c

19. The diagram shows the electric field lines in a region of space containing two small charged spheres (Y and Z) Then: a. the magnitude of the electric field is the same everywhere b. Y is negative and Z is positive c. Y is positive and Z is negative d. Y and Z must have the same sign e. the electric field is strongest midway between Y and Z

answer c

22. An isolated charged point particle produces an electric field with magnitude E at a point 2m away. At a point 1 m from the particle the magnitude of the field is: a. E b. 2E c. 4E d. E/2 e. E/4

answer c

28. A cylindrical wastepaper basket with a 0.15 m radius opening is in a uniform electric field of 300 N/C perpendicular to the opening. The total flux through the sides and bottom is: a. 0 b. 4.2 c. 21 d. 280 e. can't tell w/o knowing the areas of the sides and bottom

answer c

3. When charged particles move through a conductor such as copper wire, what moves? a. conduction neutrons b. conduction protons c. conduction electrons

answer c

11. Which can be produced in a pair production? a. two protons b. two neutrons c. and electron and a proton d. an electron and a positron e. two electrons

answer d

14. Which describes the electric field near a sphere with uniform positive charge? a. the electric field lines form concentric circles around the sphere b. the electric field lines extend radially away from the sphere on one side of the sphere and then loop around to extend radially toward the sphere on the opposite side c. the electric field lines extend radially toward the sphere d. the electric field lines extend radially away from the sphere

answer d

20. The electric field at a distance of 10 cm from an isolated point particle with a charge of 2E-9 C is a. 1.8 N/C b. 18 N/C c. 180 N/C d. 1800 N/C e. none of these

answer d

21. An isolated point charged point particle produces an electric field with magnitude E at a point 2m away from the charge. A point at which field magnitude is E/4 is: a. 0.5m away from the charge b. 1m away from the charge c. 2m away from the charge d. 4m away from the charge e. 8m away from the charge

answer d

26. When a piece of paper is held with one face perpendicular to a uniform electric field the flux through it is 25 N · m2 /C. When the paper is turned 25◦ with respect to the field the flux through it is: A. 0 B. 11 N · m2/C C. 12 N · m2/C D. 23 N · m2/C E. 25 N · m2/C

answer d

27. The flux of the electric field 24i + 30j + 16k through a 2.0 m^2 portion of the yz plane is: a. 32 b. 34 c. 42 d. 48 e. 60

answer d

29. Which statement is correct? a. the flux through a closed surface is always positive b. the flux through a closed surface is always negative c. the sign of the flux through a closed surface depends on an arbitrary choice of sign for the surface vector d. inward flux through a closed surface is negative and outward flux is positive e. inward flux through a closed surface is positive and outward flux is negative

answer d

31. A point charge is placed at the center of a spherical Gaussian surface. The electric flux is changed if: a. the sphere is replaced by a cube of the same volume b. the sphere is replaced by a cube of one-tenth the volume c. the point charge is moved off center (but still inside the original sphere) d. the point charge is moved to just outside the sphere e. a second point charge is placed just outside the sphere

answer d

34. A solid insulating sphere of radius R contains a positive charge that is distributed with a volume charge density that does not depend on angle but does increase linearly with distance from the sphere center. Which of the graphs below correctly gives the magnitude E of the electric field as a function of the distance r from the center of the sphere? a. A b. B c. C d. D e. E

answer d

25. To calculate the flux through a curved surface a. the surface must be spherical b. actually the flux through a curved surface cannot be calculated c. the surface cannot be curved very much; then you can treat it as though it were flat d. the area vector has to be perpendicular to the surface somewhere e. you must divide the surface into pieces that are tiny enough to be almost flat

answer e

32. A point particle with charge q is placed inside a cube but not at its center. The electric flux through any one side of the cube: a. is zero b. is q/E0 c. is q/4E0 d. is q/6E0 e. cannot be computed using Gauss' law

answer e

35. Positive charge Q is placed on a conducting spherical shell with inner radius R1 and outer radius R2. A point charge q is placed at the center of the cavity. The force on the charge q is: a. (Qq)/(4piE0R1^2) b. (Qq)/(4piE0(R2^2-R1^2)) c. (Qq)/(4piE0R2^2) d. (Qq)/(4piE0(R2^2+R1^2)) e. 0

answer e

36. Positive charge Q is placed on a conducting spherical shell with inner radius R1 and outer radius R2. The electric field at a point r < R1 is: a. Q/(4piE0(R1^2+r^2)) b. Q/(4piE0R1^2) c. Q/(4piE0(R1^2-r^2)) d. Q/(4piE0r^2) e. 0

answer e