PHYSICS 30 ELECTROMAGNETISM ASSIGNMENT 3 VERSION:0

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Morgan Hodge
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1 Communication includes statement of the physics concept used and how it is applied in the situation along with diagrams, word explanations and calculations in a well laid out formula, substitution, answer format. Complete communication is required. 1. An astronaut has just landed on an unknown, uninhabited planet and has to send some information about the planet back to Earth. Assume the astronaut has all of the equipment needed to perform the necessary experiments. (10.00 marks) Using physics concepts as well as any related formulas, describe procedures that could be used in order to: a) measure the magnitude and direction for the gravitational field at the astronaut's location on the unknown planet. b) determine whether or not there is an electric field at the location and, if there is, to determine its magnitude and direction. c) determine whether or not there is a magnetic field at the location and, if there is, to determine its direction. 2. An apparatus, shown below, is designed to measure the magnetic flux density of a magnet. The rectangle is a coil of 7.00 turns of width m and length m. A conventional current I of A flows anticlockwise around the loop. Under these conditions the balance is in equilibrium. (10.00 marks) a) What is the direction of the magnetic force on the lower, horizontal section of the loop? b) The force on the lower, horizontal section of the loop may be written F =. Calculate the value of using the information given above. c) The current is reversed so that it now flows clockwise with unchanged magnitude. It is found that an 8.00 g mass needs to be added to the left pan of the balance to restore equilibrium. Calculate the magnetic flux density. SMolesky@Notre Dame Page 1

2 3. A student used the apparatus shown below to measure the radius of curvature of the path of electrons as they pass through a magnetic field that is perpendicular to their path. This experimental design has the voltage as the manipulated variable, the speed calculated from the voltage, and the radius as the responding variable. (10.00 marks) Accelerating Potential Speed (10 6 m/s) Radius (10-2 m) Difference (V) a) Plot the graph of radius as a function of speed, and construct a best-fit line. b) Using the slope or other appropriate averaging technique determine the strength of the magnetic field. c) Derive the equation that would allow the student to calculate the speed of the electrons from the accelerating potential. SMolesky@Notre Dame Page 2

3 Choose the best response and place your answers, using HB pencil, on the Scantron sheet provided. 1. The Venn diagram below represents areas of overlapping concepts between electric, magnetic and gravitational forces. a. Forces that are known to be both attractive and repulsive. b. Forces that obey an inverse square relationship to distance. c. Forces responsible for a suspended particle in the Millikan Oil Droplet experiment. d. Forces used in the calculation of the velocity of an electron, in the selection zone, of a mass spectrometer. The areas that best represent a, b, c and d respectively are,,,. (Record all four digits of your answer in the numerical response section of the answer sheet) 2. Which diagram best represents magnetic flux lines around a bar magnet? a. b. c. d. SMolesky@Notre Dame Page 3

4 3. The magnetic field around an electron current-carrying wire is investigated with a compass. At which of the four positions shown in the diagram will the compass needle point towards the bottom of the page? a. 1 b. 2 c. 3 d Four long, straight wires are parallel to each other; and their cross-section forms a square. Each side of the square is 0.02 m as shown in the figure. If each wire carries a current of 8.0 A in the direction shown in the figure, determine the magnitude of the total magnetic field at P, the center of the square. a. 5.1 x 10-5 T b. 1.1 x 10-4 T c. 1.7 x 10-4 T d. 2.3 x 10-4 T e. zero tesla 5. Which one of the following statements concerning the magnetic field at the center of a long, current-carrying solenoid is true? a. The magnetic field is zero. b. The magnetic field is non-zero and nearly uniform. c. The magnetic field is independent of the number of windings. d. The magnetic field is independent of the current in the solenoid. e. The magnetic field varies as 1/r as measured from the solenoid axis. Use the following information for the following two questions Wire XY is pulled along the rails in order to produce an electric circuit. It is pulled at a constant speed v through a magnetic field of strength. As a result, a voltage V of 5.41 V is induced. SMolesky@Notre Dame Page 4

5 6. The speed at which the wire is being pulled is m/s. (Round and record your answer to three digits.) 7. The applied force on the wire required to induce a constant voltage of 5.41 V, expressed in scientific notation, is b x 10 -w N. The value of b is. (Round and record your answer to three digits.) 8. A solenoid has a length of 0.30 m, a diameter of m and 500 windings. The magnetic field at its center is T. What is the current in the windings? a. 2.9 A b. 3.0 A c. 21 A d. 170 A 9. Which of the following has units of magnetic field? a. kg C -1 s -1 b. kg A -1 s -1 c. N C -1 m -1 d. J A -1 m Four conductors of different lengths are moved through a uniform magnetic field at the same speed. Which conductor will induce the greatest EMF? a. 1 b. 2 c. 3 d. 4 SMolesky@Notre Dame Page 5

6 11. Different magnetic fields are passing through two copper rings, P and Q, as shown. Which row of the table correctly identifies the ring with the greater magnetic flux and the ring with the greater magnetic flux density? Greater Magnetic Field Greater Flux Density Greater Magnetic Field Greater Flux Density a. P P b. Q Q c. P Q d. Q P 12. A solenoid of length m and radius m is comprised of 120 turns of wire. Determine the magnitude of the magnetic field at the center of the solenoid when it carries a current of 15.0 A. a x 10-3 T b x 10-3 T c x 10-3 T d x 10-3 T e. zero tesla Use the following information for the next three questions: Mass Spectrometer Singly charged positive ions, with a mass of 8.64 x kg, are accelerated in Region I, pass through the velocity selecti in Region II and then enter an external magnetic field of 1.40 T in the separation chamber of Region III. SMolesky@Notre Dame Page 6

7 13. With reference to the directions above, given the number to match each of the descriptions below: a. The direction of the electric field in Region I. b. The direction of the electric force on the ion in Region II c. The direction of the magnetic field in Region II. d. The direction of the magnetic force at the point P. The values of a, b, c, and d, respectively, are,,, and. (Record all four digits of your answer on the answer sheet.) 14. If the ions are accelerated by a potential difference of 300 V, what is their velocity at the end of the acceleration zone. a x 10 3 m/s b x 10 4 m/s c x 10 7 m/s d x 10 5 m/s 15. What magnetic field is required in Region II in order to keep the ions on a straight path if the electric field in region II is 6000 N/C? a x 10-2 T b x 10-1 T c T d x 10-3 T 16. A closed loop carries a current that increases with time. Which one of the quantities listed below relates the EMF induced in the loop to the rate at which the current is increasing? a. resistance of the loop b. capacitance of the loop c. self-inductance of the loop d. power dissipated by the loop e. mutual inductance of the loop 17. Which statement best describes a proton that is being accelerated? a. It produces electromagnetic radiation. b. The magnitude of its charge increases. c. It absorbs a neutron to become an electron. d. It is attracted to other protons. 18. Which type of wave requires a material medium through which to travel? a. radio wave b. microwave c. light wave d. mechanical wave SMolesky@Notre Dame Page 7

8 19. A magnet moving near a loop induces a conventional current in the circuit. The current flows in the direction shown. Which of the following pairs of motions will both produce this current? A radar gun can determine the speed of a moving automobile by measuring the difference in frequency between emitted and reflected radar waves. This process illustrates: a. North pole closest to the loop magnet moving towards the loop. North pole closest to the loop magnet moving away from the loop. b. North pole closest to the loop, magnet moving away from the loop. South pole closest to the loop, magnet moving towards the loop. c. South pole closest to the loop, magnet moving away from the loop. North pole closest to the loop, magnet moving away from the loop. d. South pole closest to the loop, magnet moving towards the loop. South pole closest to the loop, magnet moving away from the loop. 20. A radar wave generated on Earth takes s to travel to an object in space and return. The distance from Earth to the object, expressed in scientific notation, is approximately, b x 10 w m. The value of b is. (Round and record your answer to three digits.) 21. Which one of the following types of wave is intrinsically different from the other four? a. radio waves b. sound waves c. gamma rays d) ultraviolet radiation e) gamma rays SMolesky@Notre Dame Page 8

9 22. Magnets and Two Different Tubes The mass of each magnet is 80.0 g and the length of each tube is 1.00 m. The correct equation to determine the magnitude of the net force acting on magnet X as it falls through the copper tube is: a. b. c. d. 23. The path of a charged particle travelling perpendicularly through a uniform magnetic field is deflected due to i and the speed of the charged particle will ii. The statement above is completed by the information in row Row i ii a. an unbalanced magnetic force stay the same b. an unbalanced magnetic force increase c. a balanced centripetal force stay the same d. a balanced centripetal force increase SMolesky@Notre Dame Page 9

10 24. When there is no current in the solenoids, the electron beam in the cathode ray tube strikes the screen at origin O. In order to move the beam to position P, which solenoid is used and what is the direction of the electric current applied? Solenoid Current Direction Solenoid Current Direction a. M W b. M X c. N Y d. N Z 25. An alpha particle is projected eastward at a speed of 6.50 x 10-3 m/s, along a line parallel to Earth's equator, where the magnitude of Earth's magnetic field is 5.00 x 10-5 T. (Assume the gravitational field to be 9.81 N/kg at this location.) Based on the above information, the equation used to determine the magnitude of the net force acting on the alpha particle is: a. F net = F mag + F b. g F net = F mag + - F c. g F = F + - f d. net mag F = -F net g SMolesky@Notre Dame Page 10

PHYSICS 3204 PUBLIC EXAM QUESTIONS (Magnetism &Electromagnetism)

PHYSICS 3204 PUBLIC EXAM QUESTIONS (Magnetism &Electromagnetism) NAME: August 2009---------------------------------------------------------------------------------------------------------------------------------