E) all of the above E) 1.9 T

Transcription

1 1. The figure shows a uniform magnetic field that is normal to the plane of a conducting loop, which has a resistance R. Which one of the following changes will cause an induced current to flow through the resistor? A) decreasing the area of the loop B) decreasing the magnitude of the magnetic field C) increasing the magnitude of the magnetic field D) rotating the loop through 90 about an axis in the plane of the paper E) all of the above 2. A conducting loop has an area of m 2 and is positioned such that a uniform magnetic field is perpendicular to the plane of the loop. When the magnitude of the magnetic field decreases to 0.30 T in s, the average induced emf in the loop is 1.2 V. What is the initial value of the magnetic field? A) 0.42 T B) 0.75 T C) 0.87 T D) 1.2 T E) 1.9 T

2 Use the following to answer questions 3-4 The figure shows a uniform, 3.0-T magnetic field that is normal to the plane of a conducting, circular loop with a resistance of 1.5 Ω and a radius of m. The magnetic field is directed out of the paper as shown. Note: The area of the non-circular portion of the wire is considered negligible compared to that of the circular loop. 3. What is the average current in the loop if the magnitude of the magnetic field is doubled in 0.4 s? A) 2.8 x 10-3 A, clockwise B) 4.5 x 10-3 A, clockwise C) 4.5 x 10-3 A, counterclockwise D) 9.0 x 10-3 A, clockwise E) 9.0 x 10-3 A, counterclockwise 4. If the magnetic field is held constant at 3.0 T and the loop is pulled out of the region that contains the field in 0.2 s, at what rate is energy dissipated in R? A) 1.8 x 10-2 W B) 3.6 x 10-2 W C) 3.8 x 10-3 W D) 2.7 x 10-4 W E) 4.9 x 10-4 W

3 Use the following to answer questions 5-6. A m long solenoid has a radius of m and turns. The current in the solenoid changes at a rate of 6.0 A/s. A conducting loop of radius m is placed at the center of the solenoid with its axis the same as that of the solenoid as shown. 5. Determine the induced emf in the loop. A) 0.7 x 10-3 V B) 1.4 x 10-3 V C) 2.8 x 10-3 V D) 8.9 x 10-3 V E) zero volts 6. Determine the self-induced emf in the solenoid due to the changing current. A) 60 V B) 98 V C) 133 V D) 180 V E) 250 V

4 7. A metal ring is released from rest below the end of a bar magnet that is fixed in position as suggested in the figure. An observer views the ring from below. Which one of the following statements concerning this situation is true? A) The ring will fall with acceleration g=9.8 m/s 2. B) The acceleration of the ring will be less than 9.8 m/s 2 C) The acceleration of the ring will be greater than 9.8 m/s 2 D) The ring will be pulled upward toward the magnet. E) The ring will remain stationary 8. A transformer has 450 turns in its primary coil and 30 turns in its secondary coil. The primary voltage is 120 Vrms at 60 Hz, and the secondary is attached to a 4 Ω resistive load. What is the rms current in the primary? A) A B) 2.6 A C) 4.0 A D) 16.0 A E) Depends on the frequency. 9. A power plant provides an rms voltage of 6.0 kv and an rms current of 150 A. The voltage is stepped up to 240 kv by a transformer before it is transmitted to a substation. The total (round trip) resistance of the transmission line between the power plant and the substation is 75 Ω. What percentage of the power produced at the power plant is lost in transmission to the substation? A) 0.47 % B) 0.41 % C) 0.34 % D) 0.23 % E) 0.12 %

5 Use the following to answer questions The voltage across and the current through a single circuit element connected to an ac generator are shown in the graph. 10. Determine the peak current through this circuit element. A) 1.0 A B) 1.4 A C) 2.0 A D) 2.8 A E) 4.0 A 11. Determine the reactance of this circuit element. A) 20 Ω B) 25 Ω C) 40 Ω D) 57 Ω E) 80 Ω 12. Which one of the following statements concerning this circuit element is true? A) The element is a resistor. B) The element is a capacitor. C) The element is an inductor. D) The element could be a resistor or an inductor. E) The element could be an inductor or a capacitor.

6 13. The graph shows the impedance as a function of frequency for a series RCL circuit. At what frequency will this circuit resonate? A) f 1 B) f 2 C) f 3 D) f 1 or f 3 E) f 1 or f 2 or f An ac generator supplies an rms voltage of 180 V at frequency f=60.0 Hz. It is connected in series with a 0.50-H inductor, a 6.0-µF capacitor and a 300-Ω resistor. What is the average power supplied to the circuit? A) 48 W B) 54 W C) 63 W D) 83 W E) 112 W 15. Which one of the following statements concerning electromagnetic waves is false? A) Electromagnetic waves carry energy. B) X-rays are not electromagnetic waves. C) In vacuum, all electromagnetic waves travel at the same speed. D) Electromagnetic waves can be produced by accelerated charges. E) The magnetic field is perpendicular to the propagation direction.

7 16. A radio wave sent from the surface of the earth reflects from the surface of the moon and returns to the earth. The elapsed time between the generation of the wave and the detection of the reflected wave is s. Determine the distance from the surface of the earth to the surface of the moon. A) m B) m C) m D) m E) m 17. The rms value of the electric field component of an electromagnetic wave is E, and the average intensity of the wave is of W/m 2. If the rms electric field were increased to 5E, what would be the intensity of the wave? A) W/m 2 B) 0.10 W/m 2 C) 0.25 W/m 2 D) 0.50 W/m 2 E) 1.0 W/m A local radio station transmits radio waves uniformly in all directions with a total power of W. What is the intensity of these waves when they reach a receiving antenna located 40.0 km from the transmitting antenna? (1 km = 1000 m). A) W/m 2 B) W/m 2 C) W/m 2 D) W/m 2 E) W/m 2

8 19. An astronomer observes electromagnetic waves emitted by oxygen atoms in a distant galaxy that have a frequency of Hz. In the laboratory on earth, oxygen atoms emit waves that have a frequency of Hz. Determine the relative velocity of the galaxy with respect to the astronomer on the earth. Note: The speed of light is m/s. A) m/s, away from earth B) m/s, toward earth C) m/s, away from earth D) m/s, toward earth E) m/s, away from earth 20. Unpolarized light of intensity S o passes through two sheets of polarizing material whose transmission axes make an angle of 60 with each other as shown in the figure. What is the intensity of the transmitted beam, S t? A) S o /4 B) S o /8 C) 3S o /4 D) S o /16 E) zero

9 21. In the figure, Joel is using a device known as a periscope to observe an object, represented by an upright arrow. The periscope contains two plane mirrors tilted at an angle of 45 relative to Joel's line of sight. Which one of the following pairs of characteristics of the final image is correct relative to those of the object? A) inverted, real B) upright, enlarged C) inverted, smaller D) inverted, same size E) upright, virtual 22. An object is placed 1 m in front of a plane mirror. An observer stands 3 m behind the object. For what distance must the observer focus his eyes in order to see the image of the object? A) 1 m B) 2 m C) 3 m D) 4 m E) 5 m

10 23. Which one of the following statements concerning the image formed by a concave spherical mirror is true? A) When the object distance is less than the focal length, the image is virtual. B) When the object distance is larger than the focal length, the image is virtual. C) When the object is at the center of curvature, the image is formed at infinity. D) When the object distance is less than the focal length, the image is inverted relative to the object. E) When the object distance is larger than the focal length, the image is upright relative to the object. 24. A concave mirror in an amusement park has a radius of curvature of 4.0 m. A child stands in front of the mirror so that she appears 2.5 times taller than her actual height. If the image is upright, how far is she standing from the mirror? A) 1.2 m B) 3.5 m C) 2.8 m D) 4.0 m E) 7.0 m