TIME OF COMPLETION DEPARTMENT OF NATURAL SCIENCES. PHYS 2212, Exam 2 Section 1 Version 1 April 16, 2014 Total Weight: 100 points

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1 TIME OF COMPLETION NAME DEPARTMENT OF NATURAL SCIENCES PHYS 2212, Exam 2 Section 1 Version 1 April 16, 2014 Total Weight: 100 points 1. Check your examination for completeness prior to starting. There are a total of ten (10) problems on eight (8) pages. 2. Authorized references include your calculator with calculator handbook, and the Reference Data Pamphlet (provided by your instructor). 3. You will have 75 minutes to complete the examination. 4. The total weight of the examination is 150 points. 5. There are six (6) multiple choice and four (4) calculation problems. Work five (5) multiple choice and four (4) calculation problems. Show all work; partial credit will be given for correct work shown. 6. If you have any questions during the examination, see your instructor who will be located in the classroom. 7. Start: 3:35 p.m. Stop: 4:50 p. m. PROBLEM POINTS CREDIT TOTAL PERCENTAGE

2 1. A charged particle is moving with speed v perpendicular to a uniform magnetic field. A second identical charged particle is moving with speed 2v perpendicular to the same magnetic field. If the frequency of revolution of the first particle is f, the frequency of revolution of the second particle is a. f/4. b. f. c. 2f. d. 4f. e. f/2. 2. Which of the following statements are true? Check all that apply. a. Earth's geographic north pole is actually a magnetic south pole. b. The south poles of two bar magnets will repel each other. c. The north poles of two bar magnets will attract each other. d. Scientists have evidence that single isolated magnetic poles, called magnetic monopoles, exist. e. Earth's geographic south pole is also a magnetic south pole. f. The north pole of a bar magnet will attract the south pole of another bar magnet. 3. Consider a magnetic force acting on an electric charge in a uniform magnetic field. Which of the following statements are true? Check all that apply. a. An electric charge moving perpendicular to a magnetic field experiences a magnetic force. b. A magnetic force is exerted on a stationary electric charge in a uniform magnetic field. c. A magnetic force is exerted on an electric charge moving through a uniform magnetic field. (Continued on the next page.)

3 d. The direction of the magnetic force acting on a moving charge in a magnetic field is perpendicular to the direction of the magnetic field. e. An electric charge moving parallel to a magnetic field experiences a magnetic force. f. The direction of the magnetic force acting on a moving electric charge in a magnetic field is perpendicular to the direction of motion. 4. Which of the following statements are true for magnetic force acting on a current-carrying wire in a uniform magnetic field? Check all that apply. a. The magnetic force on the current-carrying wire is strongest when the current is parallel to the magnetic field lines. b. The magnetic force on the current-carrying wire is strongest when the current is perpendicular to the magnetic field lines. c. The direction of the magnetic force acting on a current-carrying wire in a uniform magnetic field is perpendicular to the direction of the current. d. The direction of the magnetic force acting on a current-carrying wire in a uniform magnetic field is perpendicular to the direction of the field. 5. A long, straight, vertical wire carries a current upward. Due east of this wire, in what direction does the magnetic field point? a. west b. south c. upward d. downward e. east f. north

4 6. Two long parallel wires are placed side by side on a horizontal table. The wires carry equal currents in the same direction. Which of the following statements are true? Check all that apply. a. The magnetic field is a maximum at a point midway between the two wires. b. The magnetic force between the two wires is repulsive. c. The magnetic force between the two wires is attractive. d. The magnetic field at a point midway between the two wires is zero. 7. As shown in the figure, a small particle of charge q = C and mass m = kg has velocity v o = m/s as it enters a region of uniform magnetic field. The particle is observed to travel in the semicircular path shown, with radius R = 5.0 cm. a. Calculate the magnitude of the magnetic field in the region. mv r q B mv B q r T b. What is the direction of the magnetic field? Into the page

5 c. How long does it take the particle to leave the magnetic field? r t 13.5 V s 8. Given the network, write equations that would allow you to solve for the currents in each resistor. Label and indicate your choices for current directions. DO NOT SOLVE THE EQUATIONS. You MAY nevertheless solve the equations for the extra 5 points, if correct. Assume R 1 = 2.00 Ω, R 2 = 6.00 Ω, and V = 10.0 V.) a. My choices for the currents are: I 1 through R 1 upward, I 2 through 5 and 1 downward, and I 3 through 3 and R 2 downward Solutions are: I 1 = A I 2 = A I 3 = A 9. A straight 3.00 m wire carries a typical household current of 1.50 A (in one direction) at a location where the earth's magnetic field is gauss from South to North. a. Find the direction of the force that our planet's magnetic field exerts on this cord if is oriented so that the current in it is running from west to east. Upward, out of the page

6 b. Find the magnitude of the force that our planet's magnetic field exerts on this cord if is oriented so that the current in it is running from west to east. F IlB sin N c. Find the direction of the force that our planet's magnetic field exerts on this cord if is oriented so that the current in it is running vertically upward. To the left, west d. Find the magnitude of the force that our planet's magnetic field exerts on this cord if is oriented so that the current in it is running vertically upward. F IlB sin N e. Is the magnetic force ever large enough to cause significant effects under normal household conditions? Of course not! 9. A rigid rectangular loop, which measures 0.30 m by 0.40 m, carries a current of 5.5 A, as shown in the figure. A uniform external magnetic field of magnitude 2.9 T in the negative x direction is present. Segment CD is in the xz-plane and forms a 35 angle with the z-axis, as shown.

7 a. Calculate the net magnetic force acting on the loop. Zero, closed current loop inside constant magnetic field experiences NO magnetic force. b. What is the torque that the magnetic field exerts on the loop? ( 1.098Nm)( j) F COMPLETION NAME SOLUTION DEPARTMENT OF NATURAL SCIENCES PHYS 2212, Exam 2 Section 1 Version 2 April 16, 2014 Total Weight: 100 points 1. Check your examination for completeness prior to starting. There are a total of ten (10) problems on eight (8) pages. 2. Authorized references include your calculator with calculator handbook, and the Reference Data Pamphlet (provided by your instructor). 3. You will have 75 minutes to complete the examination. 4. The total weight of the examination is 150 points.

8 5. There are six (6) multiple choice and four (4) calculation problems. Work five (5) multiple choice and four (4) calculation problems. Show all work; partial credit will be given for correct work shown. 6. If you have any questions during the examination, see your instructor who will be located in the classroom. 7. Start: 3:35 p.m. Stop: 4:50 p. m. PROBLEM POINTS CREDIT TOTAL PERCENTAGE

9 10. A charged particle is moving with speed v perpendicular to a uniform magnetic field. A second identical charged particle is moving with speed 2v perpendicular to the same magnetic field. If the orbital period of the first particle is T, the orbital period of the second particle is a. T/4. b. T. c. 2T. d. 4T. e. T/ Which of the following statements are true? Check all that apply. a. Earth's geographic north pole is actually a magnetic south pole. b. The south poles of two bar magnets will repel each other. c. The north poles of two bar magnets will attract each other. d. Scientists have evidence that single isolated magnetic poles, called magnetic monopoles, exist. e. Earth's geographic south pole is also a magnetic south pole. f. The north pole of a bar magnet will attract the south pole of another bar magnet. 12. Consider a magnetic force acting on an electric charge in a uniform magnetic field. Which of the following statements are true? Check all that apply. a. An electric charge moving perpendicular to a magnetic field experiences a magnetic force. b. A magnetic force is exerted on a stationary electric charge in a uniform magnetic field. c. A magnetic force is exerted on an electric charge moving through a uniform magnetic field. (Continued on the next page.)

10 d. The direction of the magnetic force acting on a moving charge in a magnetic field is perpendicular to the direction of the magnetic field. e. An electric charge moving parallel to a magnetic field experiences a magnetic force. f. The direction of the magnetic force acting on a moving electric charge in a magnetic field is perpendicular to the direction of motion. 13. Which of the following statements are true for magnetic force acting on a current-carrying wire in a uniform magnetic field? Check all that apply. a. The magnetic force on the current-carrying wire is strongest when the current is parallel to the magnetic field lines. b. The magnetic force on the current-carrying wire is strongest when the current is perpendicular to the magnetic field lines. c. The direction of the magnetic force acting on a current-carrying wire in a uniform magnetic field is perpendicular to the direction of the current. d. The direction of the magnetic force acting on a current-carrying wire in a uniform magnetic field is perpendicular to the direction of the field. 14. A long, straight, vertical wire carries a current downward. Due east of this wire, in what direction does the magnetic field point? a. west b. south c. upward d. downward e. east f. north PHYS 2212 Exam 2, Version 1 Spring

11 15. Two long parallel wires are placed side by side on a horizontal table. The wires carry equal currents in the same direction. Which of the following statements are true? Check all that apply. a. The magnetic field is a maximum at a point midway between the two wires. b. The magnetic force between the two wires is repulsive. c. The magnetic force between the two wires is attractive. d. The magnetic field at a point midway between the two wires is zero. 16. As shown in the figure, a small particle of charge q = C and mass m = kg has velocity v o = m/s as it enters a region of uniform magnetic field. The particle is observed to travel in the semicircular path shown, with radius R = 5.0 cm. d. Calculate the magnitude of the magnetic field in the region. mv r q B mv B q r T PHYS 2212 Exam 2, Version 1 Spring

12 e. What is the direction of the magnetic field? Out of the page f. How long does it take the particle to leave the magnetic field? r t 12.5 V s 17. Given the network, write equations that would allow you to solve for the currents in each resistor. DO NOT SOLVE THE EQUATIONS. You MAY nevertheless solve the equations for the extra 5 points, if correct. Assume R = 2.00 Ω, 1 = 6.00 V, and 2 = 3.00 V.) Solutions are: I 1 = A I 2 = A I 3 = A PHYS 2212 Exam 2, Version 1 Spring

13 9. A straight 2.00 m wire carries a typical household current of 1.50 A (in one direction) at a location where the earth's magnetic field is gauss from South to North. f. Find the direction of the force that our planet's magnetic field exerts on this cord if is oriented so that the current in it is running from west to east. Upward, out of the page g. Find the magnitude of the force that our planet's magnetic field exerts on this cord if is oriented so that the current in it is running from west to east. F IlB sin N West, to the left h. Find the direction of the force that our planet's magnetic field exerts on this cord if is oriented so that the current in it is running vertically upward. i. Find the magnitude of the force that our planet's magnetic field exerts on this cord if is oriented so that the current in it is running vertically upward. F IlB sin N j. Is the magnetic force ever large enough to cause significant effects under normal household conditions? No, too small. PHYS 2212 Exam 2, Version 1 Spring

14 18. A rigid rectangular loop, which measures 0.30 m by 0.40 m, carries a current of 5.5 A, as shown in the figure. A uniform external magnetic field of magnitude 2.9 T in the negative x direction is present. Segment CD is in the xz-plane and forms a 35 angle with the z-axis, as shown. a. Calculate the net magnetic force acting on the loop. Zero, closed current loop inside constant magnetic field experiences NO magnetic force. b. What is the torque that the magnetic field exerts on the loop? ( 1.098Nm)( j) PHYS 2212 Exam 2, Version 1 Spring