Exam 1--PHYS 102--S16

Transcription

1 Name: Exam 1--PHYS 102--S16 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. The up-quark, u, has an elementary charge of +(2/3)e and the down-quark, d, of -(1/3)e. What combination of three of these quarks makes up a neutron? a. uud b. udd c. ddd d. uuu 2. You bring a negatively charged rod near to a neutral copper wire, as in this figure. Which of these statements is true? a. The wire will move away from the rod b. Negative charges will move to the right-hand side of the wire. c. Nothing will happen unless the two objects touch d. Positive charges will move to the left-hand side of the wire. e. Negative charges will move to the center of the wire. 3. Imagine two charges, A & B. Charge A is attracted to a positive charge. Charge B is repelled from a negative charge. What happens if you bring charges A& B near to one another? 4. Doug rubs a piece of fur on a hard rubber rod, giving the rod a negative charge. What happens? a. The fur is left neutral. b. The fur is also charged negatively. c. Electrons are added to the rod. d. Protons are removed from the rod. 5. Two electrons and a third charged particle are located at different positions along a straight line. Both electrons experience zero net force due to static electricity. Is the charge on the third particle positive or negative, and where must it be located on the line, relative to the electrons? a. negative, in between the electrons b. positive, in between the electrons c. negative, with both electrons on the same side d. positive, with both electrons on the same side 6. The diagram shows three heavily charged plastic cubes. The net force on cube #3 is shown. If cube #3 is positively charged, what are the charges on cubes 1 and 2, respectively? a. cube 1 is positive; cube 2 is negative b. cube 1 is positive; cube 2 is positive c. cube 1 is negative; cube 2 is positive d. cube 1 is positive; cube 2 is negative a. they attract b. they repel c. nothing; they neither attract nor repel d. there is not enough information; you must know the charge of A & B 1

2 7. What is the magnitude of the force on the +2 nc charge in this figure? 9. The force between two charges, which are separated by 4 m, is 12 N. If the two charges are brought closer to a distance of 2 m, what is the force? a. 48 N b. 24 N c. 12 N d. 6 N e. 3 N 10. This figure shows 2 metal spheres that each have a charge. If q 2 has a charge with a magnitude of 3 C, what is the charge on q 1? a. 0 N b. 5.1x10-8 N c. 1.0x10-8 N d. 1.3x10-7 N e. 1.8x10-8 N 8. For the figure in the previous question, what is the direction of the force on the 2 nc charge? a C b. +6 C c. -3 C d. +11 C a. 11 above the -x axis b. 37 above the +x axis c. 11 above the +x axis d. along the -y axis e. 53 below the -x axis 2

3 11. For this figure, what is the magnitude of the electric field at point A? 13. Electric field is. a. a measure of energy per unit charge. b. a measure of force per unit charge. c. a conservative force. d. always quantized. e. equal to the force on a charged particle. 14. Consider this configuration of charges. At what point is the electric field equal to zero? (Point C is equidistant between the 2 charges.) a. a b. b c. c d. d e. e a. 2.0 N/C b. 3.0 N/C c. 2.2 N/C d. 1.0 N/C e. 1.4 N/C 15. A proton is accelerated by a constant electric field of magnitude 220 N/C; the proton is moving in the same direction as the electric field. What is the proton s velocity after 1x10-6 s? 12. For the figure in the previous question, what is the direction of the electric field at point A? a. 237º from the +x axis b. 63º below the +x axis c. in the -y direction d. 27º above the +x axis e. in the +x direction a. 2.1x10 10 m/s b. 3.5x10-23 m/s c. 2.1x10 4 m/s d m/s 16. A parallel-plate capacitor initially has a potential difference of 10 V and is then disconnected from the charging battery. If the area of the plates is now doubled, what is the new value of the voltage? a. 2.5 V b. 5 V c. 10 V d. 20 V e. 40 V 3

4 17. A parallel-plate capacitor has dimensions 0.04 m 0.05 m. The plates are separated by a 1.0 x10-3 m thickness of paper (dielectric constant κ = 3.7). What is the charge that can be stored on this capacitor, when connected to a 1.5-V battery? 19. This diagram shows a collection of charges. At which point is the potential equal to zero? a C b C c C d C e C 18. Inserting a dielectric material between two charged parallel conducting plates, originally separated by air and disconnected from a battery, will produce what effect on the capacitor? I. Increase charge on the capacitor II. Increase voltage of the capacitor III. Increase capacitance of the capacitor IV. Decrease capacitance of the capacitor a. IV only b. III only c. I, II, and III d. II & IV e. I & III a. a b. b c. c d. d e. at all points 20. Which of these is a unit for the electric potential? I. J C II. Volts III. kg m2 s 4 C a. I b. I & II c. II & III d. I & III e. all of these are units for the potential 4

5 21. For this scenario, where is the electric potential the least? 24. This figure shows two charges. What is the potential at point A? a. both A & D b. B c. C d. A e. both C & B 22. The electric potential 1m from a certain charged particle is 4 times the potential at 1m from a second particle. How do the particles charges compare? a. The first particle has one-quarter (1/4) the charge of the second particle. b. The first particle has 2 times the charge of the second particle. c. The first particle has one-half the charge of the second particle. d. The first particle has 4 times the charge of the second particle. a. -9 V b. 27 V c. 18 V d. -10 V e. -18 V 23. If the distance between two negative point charges is increased by a factor of three, the resultant potential energy is what factor times the initial potential energy? a. 9.0 b. 1/9 c. 3.0 d. 1/3 5

6 ID: A Exam 1--PHYS 102--S16 Answer Section MULTIPLE CHOICE 1. ANS: B PTS: 1 REF: S16-CC 2. ANS: B PTS: 1 REF: S16 3. ANS: B PTS: 1 REF: S16 4. ANS: C PTS: 1 REF: S16 5. ANS: B PTS: 1 REF: S16-CC 6. ANS: B PTS: 1 REF: S16 7. ANS: C PTS: 1 REF: S16 8. ANS: D PTS: 1 REF: S16 9. ANS: A PTS: 1 REF: S ANS: B PTS: 1 REF: S ANS: C PTS: 1 REF: S ANS: B PTS: 1 REF: S ANS: B PTS: 1 REF: S ANS: B PTS: 1 REF: S ANS: C PTS: 1 REF: S ANS: B PTS: 1 REF: S ANS: E PTS: 1 REF: S ANS: B PTS: 1 REF: S ANS: E PTS: 1 REF: S ANS: B PTS: 1 REF: S ANS: A PTS: 1 REF: S ANS: D PTS: 1 REF: S16-CC 23. ANS: D PTS: 1 REF: S ANS: A PTS: 1 REF: S16 1