2. Determine the excess charge on the outer surface of the outer sphere (a distance c from the center of the system).

Transcription

1 Use the following to answer question 1. Two point charges, A and B, lie along a line separated by a distance L. The point x is the midpoint of their separation. 1. Which combination of charges will yield zero electric potential at the point x? A) +1q and 1q B) +2q and 3q C) +1q and 4q D) 1q and +4q E) +4q and +4q Use the following to answer questions 2-3. A solid, conducting sphere of radius a carries an excess charge of +6 µc. This sphere is located at the center of a hollow, conducting sphere with an inner radius of b and an outer radius of c as shown. The hollow sphere also carries a total excess charge of +6 µc. 2. Determine the excess charge on the outer surface of the outer sphere (a distance c from the center of the system). A) zero coulombs B) 6 µc C) +6 µc D) +12 µc E) 12 µc Version A Page 1

2 3. Which one of the following figures shows a qualitatively accurate sketch of the electric field lines in and around this system? Answer: (e) Version A Page 2

3 4. Four point charges are held fixed at the corners of a square as shown in the figure. Which of the five arrows shown below most accurately shows the direction of the net force on the charge Q due to the presence of the three other charges? Answer: E A) B) C) D) E) 5. Two positive point charges are separated by a distance R. If the distance between the charges is reduced to R/2, what happens to the total electric potential energy of the system? A) It remains the same. B) It is doubled. C) It increases by a factor of 4. D) It is reduced to one-half of its original value. E) It is reduced to one-fourth of its original value. Use the following to answer questions 6-7. Two charges of opposite sign and equal magnitude Q = 2.0 C are held 2.0 m apart as shown in the figure. Version A Page 3

4 6. Determine the magnitude of the electric field at the point P. A) V/m B) V/m C) V/m D) V/m E) zero V/m 7. Determine the electric potential at the point P. A) V B) V C) V D) V E) zero volts 8. A parallel plate capacitor with plates of area A and plate separation d is charged so that the potential difference between its plates is V. If the capacitor is then isolated and its plate separation is decreased to d/2, what happens to the potential difference between the plates? A) The potential difference is increased by a factor of four. B) The potential difference is twice it original value. C) The potential difference is one half of its original value. D) The potential difference is one fourth of its original value. E) The potential difference is unchanged. Use the following to answer question 9. Three resistors are placed in a circuit as shown. The potential difference between points A and B is 30 V. 9. What is the potential drop across the 30-Ohm resistor? A) 10 V B) 20 V C) 30 V D) 60 V E) 100 V Version A Page 4

5 10. An electron traveling horizontally enters a region where a uniform magnetic field is directed into the plane of the paper as shown. Which one of the following phrases describes a possible path of the electron after it first enters the field? TWO POSSIBLE ANSWERS A) upward following closed circle B) downward following a closed circle C) upward following a semicircle before leaving the region D) downward following a semicircle before leaving the region E) downward following a quarter-circle before leaving the region Use the following to answer question 11. Two coils, 1 and 2, with iron cores are positioned as shown in the figure. Coil 1 is part of a circuit with a battery and a switch. Version A Page 5

6 11. Immediately after the switch S is closed, which one of the following statements is true? A) An induced current begins to flow from left to right in R. B) An induced current begins to flow from right to left in R. C) A magnetic field that points toward B appears inside coil 1. D) An induced magnetic field that points toward B appears inside coil 2. E) There will be no current through R. Use the following to answer question A rectangular loop is moving toward the right with speed v. At the instant shown, the loop is partially in and partially out of a region of uniform magnetic field that is directed into the paper. If the current in the loop flowed counterclockwise, it would violate Lenz's law. Which of the following would be a consequence? A) The loop would come to rest due to the magnetic force. B) The magnitude of the loop's velocity would INCREASE exponentially. C) The magnitude of the loop's velocity would DECREASE exponentially, but never reach zero. D) The loop's velocity would be constant. E) The loop would rotate about an axis parallel to B. 13. The average AC power supplied to a certain circuit is non-zero and independent of the frequency for an fixed rms voltage. Which combination of elements is most likely to comprise the circuit? A) capacitors only B) inductors only C) resistors only D) a combination of inductors and resistors E) a combination of inductors and capacitors Version A Page 6

7 14. An incandescent light bulb radiates uniformly in all directions with a total average power of W. What is the maximum value of the magnetic field at a distance of 0.50 m from the bulb? A) T B) T C) T D) T E) zero tesla 15. Which of the following most accurately describes how a lens focuses parallel light rays of one frequency to an approximate focal point? A) Different rays have different speeds in the lens B) The index of refraction of the lens depends on wavelength C) Different rays have different wavelengths in the lens D) Different rays have different frequencies in the lens E) Different rays have different angles of incidence and transmission 16. An object is placed 30 cm in front of a concave spherical mirror that has a radius of curvature 40 cm. Which one of the following phrases best describes the image? A) virtual and located at infinity B) real and located 60 cm from the mirror C) real and located 120 cm from the mirror D) virtual and located 60 cm from the mirror E) virtual and located 120 cm from the mirror Version A Page 7

8 17. A glass block with an index of refraction of 1.7 is immersed in an unknown liquid. A ray of light inside the block undergoes total internal reflection as shown in the figure. Which one of the following relations best indicates what may be concluded concerning the index of refraction of the liquid, n L? A) n L < 1.0 B) n L > 1.3 C) n L > 1.1 D) n L < 1.3 E) n L < When an object is placed 25 cm from a lens, a real image is formed. Which one of the following conclusions is incorrect? A) The image is upright. B) The lens is a converging lens. C) The image may be reduced or enlarged. D) The image distance can be less than 25 cm. E) The focal length of the lens is less than 25 cm. Use the following to answer question 19. An object is placed 20.0 cm from a converging lens with focal length 15 cm. A concave mirror with focal length 10 cm is located 75 cm to the right of the lens as shown in the figure. Note: The figure is not drawn to scale. Version A Page 8

9 19. Determine the location of the final image. A) 48 cm to the right of the lens B) 96 cm to the right of the lens C) 30 cm to the left of the mirror D) cm to the left of the mirror E) cm to the right of the mirror 20. Monochromatic light of wavelength λ is normally incident on a soap film in air. The soap film's index of refraction is n. In terms of the wavelength, what is the thickness of the thinnest film for which the reflected light will be a maximum? A) λ/4n B) λ/2n C) 3 λ/4n D) λ/ν E) 3 λ/2n 21. Which one of the following statements best explains why the diffraction of audible sound is more apparent than the diffraction of visible light? A) Sound requires a physical medium for propagation. B) Sound waves are longitudinal, and light waves are transverse. C) Light waves can be represented by rays while sound waves cannot. D) The speed of sound in air is six orders of magnitude smaller than that of light. E) The wavelength of light is considerably smaller than the wavelength of sound. 22. Light from a red laser passes through a single slit to form a diffraction pattern. If the width of the slit is increased by a factor of two, what happens to the width of the central maximum? Note: Assume that the wavelength of light is much smaller than the slit width A) The width of the central maximum increases by a factor of 4. B) The width of the central maximum decreases by a factor of 2. C) The width of the central maximum decreases by a factor of 4. D) The width of the central maximum increases by a factor of 2. E) The width of the central maximum does not change. 23. The mean lifetime of a muon at rest is s. A beam of muons is moving with speed 0.6c relative to an observer in an intertial frame. As measured by the observer, how far will an average muon travel before it decays? A) 288 m B) 360 m C) 500 m D) 600 m E) 800 m Version A Page 9

10 24. In the Compton scattering experiment shown in the figure, a monochromatic beam of X- rays strikes a target containing free electrons. Scattered X-rays are detected with a wavelength of m at an angle of 45 away from the original beam direction. What is the wavelength of the incident monochromatic X-rays? A) m B) m C) m D) m E) m 25. A beam of electrons is incident on a single slit that has a width of m and a diffraction pattern is observed on a screen located 15.0 m from the slit. The momentum of an individual electron in the beam is kg m/s. What is the width of the central maximum fringe? A) m B) m C) m D) m E) m 26. According to the quantum mechanical picture of the atom, which one of the following is a true statement concerning the ground state electron in a hydrogen atom? A) The ground state electron has zero kinetic energy. B) The ground state electron has zero binding energy. C) The ground state electron has zero ionization energy. D) The ground state electron has zero orbital angular momentum. E) The ground state electron has zero spin angular momentum. Version A Page 10

11 27. Which one of the following electronic configurations corresponds to an atomic ground state? A) 1s 2 2s 1 2p 6 B) 1s 1 2s 1 2p 1 C) 1s 1 2s 2 3p 1 D) 1s 2 2s 2 2p 1 E) 1s 1 2s 2 2p 1 Use the following to answer question 28. Consider the following nuclear decay: 28. Determine the amount of energy released in this decay. Use the following atomic masses: Conversion factors: 1 u = MeV; 1 ev = J A) J B) J C) J D) J E) J 29. How many neutrons are there in the nucleus? A) 82 B) 123 C) 205 D) 246 E) An isotope of krypton has a half-life of 3 minutes. A sample of this isotope produces 1500 counts per minute in a Geiger counter. Determine the activity after 15 minutes. A) zero B) Bq C) 0.78 Bq D) 1.5 Bq E) Bq Version A Page 11

12 31. Leptons, (e.g. electrons and muons) are apparently point-like. Hadrons (e.g. neutrons and protons) are not point-like. Which of the following provides the best evidence that hadrons (e.g neutrons and protons, etc.) are not point-like? A) The strong force acts only on protons and not on neutrons B) The gold atom is much larger than an alpha particle C) Nuclei have energy levels described by the Bohr model D) The neutron magnetic moment is not zero E) All of these 32. Which of the following describes the main reason the RBE for alpha particles is 20 while that for betas is 1? A) Helium does not react chemically with cells B) Alphas are positively charged C) Neutrinos are emitted with betas D) Alphas loose energy over a shorter range in tissue E) None of these Version A Page 12