Class: Date: Exam 3--Sp 08 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. A wire carries a current of 2 A in a direction that makes an angle of 20º with the direction of a magnetic field of strength 0.5 T. What is the magnetic force on a 5.0 m length of the wire? a. 1.7 N c. 4.7 N b. 5.0 N d. 10 N 2. A current of 10 ma is in a circular loop with 1 turn of wire. The loop produces a magnetic field of 1.26 10-8 T. If the number of turns of wire in the loop is increased to 8, what is the magnetic field produced? a. 1.01 10-7 T c. 1.58 10-9 T b. 1.26 10-8 T d. Not enough information 3. An electron moving freely in a circular path perpendicular to a constant magnetic field takes 1.00 µs to complete one revolution. What is the magnitude of the magnetic field? a. 10 6 T c. 0.007 T b. 3.6 10-5 T d. 3.45 T 1
4. Two parallel wires are 10 cm apart. One wire carries a current of 5 A to the left. The other carries a current of 2 A to the right. What is the force acting on the wires if their length is 12 meters? a. 0.12 N, repelling c. 2 10-3 N, attracting b. 2.4 10-4 N, repelling d. 2.4 10-4 N, attracting 5. What is the initial direction of this electron when it enters the magnetic field as shown? a. out of the page d. right b. left e. up c. into the page 6. A positively charged particle is traveling to the right and experiences a downward force. What is the direction of the magnetic field acting on this particle? a. left d. right b. out of the page e. down c. into the page 2
7. A wire carries a current and sits in a magnetic field as shown. What is the direction of the force on the wire? a. up d. out of the page b. into the page e. left c. down 8. A proton enters an electric field as shown. What must be the direction of a magnetic field, B, such that the proton will go undeflected? a. left d. out of the page b. up e. right c. into the page 3
9. This figure shows the schematic for an electric motor. When a current goes through the wire, the wire experiences a force and rotates along the central axis. With the direction of the current as shown, what direction does the loop rotate? a. It doesn t rotate c. Counterclockwise b. Clockwise d. It osciallates back and forth 10. Which pole of the magnet in a compass points towards the geographic north pole (where Santa lives)? a. depends on where you are on the Earth c. North b. South d. none of these 4
11. A charged particle enters a mass spectrometer. The magnetic field inside the device is 0.35 T, the velocity of the particle is 1.79x10 6 m/s, and the radius of the particle s path is 0.16 m. From the information given here, what is this particle? Particle Mass Charge Hydrogen 1.67x10-27 kg 1.6x10-19 C Deuterium 3.35x10-27 kg 1.6x10-19 C Tritium 5.01x10-27 kg 1.6x10-19 C Helium-3 5.01x10-27 kg 3.2x10-19 C a. Hydrogen c. Helium-3 b. Tritium d. Deuterium 12. This figure shows the trajectory of a charged particle in a magnetic field. Which of these best describes the charge of this particle? a. positively charged c. negatively charged b. not enough information given d. neutrally charged 5
13. This figure shows 3 configurations of four wires, which are either going into or coming out of the page. Which has the largest magnetic field at the point p, which is equidistant from each of the four wires? a. A c. C b. B d. All the same 14. Light travels through a slab of glass of thickness 2.0 cm. How much time is required for it to traverse the thickness of the glass? The index of refraction for glass is 1.5. a. 6 10 6 seconds c. 7 10-11 seconds b. 1 10-10 seconds d. 4 10-11 seconds 6
15. This figure shows a ray of light in a glass slab and incident at the air-glass interface. If θ 1 =20, what is the angle of the ray, from the perpendicular dashed line, as it emerges from the glass into the air? (The index of refraction for glass is 1.5) a. 45 c. 20 b. 13 d. 31 16. This figure shows a ray of light in a glass slab and incident at the air-glass interface. What must θ 1 be for total internal reflection to occur? (The index of refraction for glass is 1.5) a. 20 c. 42 b. Total internal reflection will not occur d. 31 7
17. In this image, a man is preparing to shoot the fish with his handgun. The actual position of the fish is shown. Should the man aim above or below the position where he sees the fish? a. above c. directly at the fish he sees b. below d. none of these 18. A scuba diver sees the Sun from below the surface of the water. Does the image of the Sun, as seen by the scuba diver, appear above or below the actual position of the Sun? a. Above c. At the same position as the Sun b. Below d. Not enough information 19. In a vacuum, light has a wavelength of 300 nm. What is its frequency? a. 90 Hz c. 1x10-15 Hz b. 300 Hz d. 1x10 15 Hz 20. Which photon from the following portions of the electromagnetic spectrum has the highest energy? a. microwaves c. infrared light b. Radio waves d. Visible light 8
21. Which of the following is true? a. n 1 <n 2 c. n 1 =n 2 b. n 1 >n 2 d. Not enough information 22. What physical property of glass allows for the creation of light-dispersing prisms? a. the triangular shape of prisms c. light travels slower in glass than air b. the dependence of the index of refraction on wavelength d. the index of refraction for glass is higher than that of air 23. What is the speed of light in glass (n=1.5)? a. 4.5 10 8 m/s c. 3.0 10 8 m/s b. 2 10 8 m/s d. 0.5 10 8 m/s 24. Light is incident on a glass plane mirror, as shown in this figure, with an incident angle of 30. What is the reflected angle? (The index of refraction for glass is 1.5) a. 45 c. 19 b. 30 d. 49 25. Isaac Newton proposed that light acted as a particle. Which of these physical phenomena led him to this conclusion? a. interference c. photoelectric effect b. refraction d. reflection 9
26. Thomas Young believed that light acted as a wave. Which physical phenomena led him to this conclusion? a. photoelectric effect c. interference b. reflection d. refraction 27. Rainbows are primarily the result of which physical phenomena: a. gravity c. reflection b. leprechauns d. refraction 28. The correct answer for this question is A. a. A c. C b. B d. D 10
Exam 3--Sp 08 Answer Section MULTIPLE CHOICE 1. ANS: A PTS: 1 2. ANS: A PTS: 1 3. ANS: B PTS: 1 4. ANS: B PTS: 1 5. ANS: C PTS: 1 6. ANS: B PTS: 1 7. ANS: A PTS: 1 8. ANS: D PTS: 1 9. ANS: B PTS: 1 10. ANS: C PTS: 1 11. ANS: B PTS: 1 12. ANS: A PTS: 1 13. ANS: B PTS: 1 14. ANS: B PTS: 1 15. ANS: D PTS: 1 16. ANS: C PTS: 1 17. ANS: B PTS: 1 18. ANS: A PTS: 1 19. ANS: D PTS: 1 20. ANS: D PTS: 1 21. ANS: B PTS: 1 22. ANS: B PTS: 1 23. ANS: B PTS: 1 24. ANS: B PTS: 1 25. ANS: D PTS: 1 26. ANS: C PTS: 1 27. ANS: D PTS: 1 28. ANS: A PTS: 1 1