1. What type of material can be induced to become a temporary magnet? A) diamagnetic B) ferromagnetic C) monomagnetic D) paramagnetic

Transcription

1 Assignment 1 Magnetism and Electromagnetism Name: Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. Show appropriate workings. 1. What type of material can be induced to become a temporary magnet? A) diamagnetic B) ferromagnetic C) monomagnetic D) paramagnetic 2. Which is the strongest magnet? A) B) C) D) 3. Which best represents the magnetic field around a bar magnet? A) C) B) D) 4. In the diagram below, a current travels through a cell phone antenna. What is the direction of the magnetic field around the antenna? A) clockwise (viewed from above B) counterclockwise (viewed from above) C) down D) up 5. Who discovered that a magnetic field is created around a current-carrying wire? A) Faraday B) Kirchoff C) Lenz D) Oersted

2 6. Which represents the magnetic field produced around the straight current-carrying conductor below? A) B) C) D) 7. In a magnetically levitated train, a permanent magnet mounted on the train is repelled by an electromagnet in the rail to keep the train above the rail. If the permanent magnet in each diagram below is identical and the current is the same in each electromagnet, which design will produce the greatest repulsion? A) C) B) D) 8. What is the force on a 2.1 m long wire, carrying 0.56 A of current, placed perpendicularly in a 4.6 x 10-4 T magnetic field? A) 1.2 x 10-4 N B) 5.4 x 10-4 N C) 2.0 x 10-3 N D) 8.2 x 10 3 N

3 9. What are the magnetic poles of the current-carrying solenoid in the diagram below? Pole A Pole B A) North North B) North South C) South North D) South South 10. As switch S is closed in the diagram below, in which direction does the compass needle point? A) East B) North C) North D) West 11. A long conductor is placed in a 0.65 T magnetic field as shown below. What are the magnitude and direction of the current that produces a 1.6 N force on the wire directed up the page? MAGNITUDE OF CURRENT DIRECTION OF CURRENT A) 4.4 A Right B) 4.4 A Left C) 11 A Right D) 11 A Left 12. A 1.0 m wire carrying a current of 10 A is oriented parallel to a uniform magnetic field of 0.40 T. What is the magnitude of the force that it experiences? A) 0 N B) 2.0 N C) 4.0 N D) 8.0 N

4 13. A 1.50 m long conductor, floating above a 5.00 x 10-3 T magnetic field, is held in static equilibrium by the field. If it is perpendicular to the magnetic field and carries a current of 25.0 A, what is the mass of the conductor? A) 1.28 x 10-2 kg B) 1.91 x 10-2 kg C) 1.88 x 10-1 kg D) 2.55 x 10 0 kg 14. What is the current in a straight conductor if it produces a magnetic field of 1.5 x 10-5 T at 0.15 m from the conductor? A) A B) A C) 11 A D) 35 A 15. An electron travelling at 1.9 x 10 4 m/s is deflected with a force of 3.0 x N in a direction perpendicular to a magnetic field. What is the strength of the magnetic field? A) 9.1 x T B) 1.6 x T C) 9.9 x 10-4 T D) 1.0 x 10 3 T 16. A proton is shot into a magnetic field at a right angle with a speed of 2.0 x 10 5 m/s. What is the strength of a magnetic field required to keep the proton in a horizontal circular orbit, if the radius of the orbit is 1.0 cm? A) 1.1 x 10-6 T B) 1.1 x 10-4 T C) 2.1 x 10-3 T D) 2.1 x 10-1 T 17. Which occurs when protons and electrons enter a magnetic field that is parallel to their direction of motion? A) Both protons and electrons are deflected. B) Neither protons nor electrons are deflected. C) Only electrons are deflected. D) Only protons are deflected. 18. A negative particle is shot into an electric field as shown. Which way will the particle be deflected? A) vertically upward B) vertically downward C) perpendicular to the plane and towards the S pole D) perpendicular to the plane and towards the N pole

5 19. An electron is moving through the uniform magnetic field below. In what direction will the electron be deflected? A) bottom of the page B) left C) right D) top of the page 20. What is the direction of the magnetic force on an electron moving near a current-carrying wire as shown? A) left B) right C) into the page D) out of the page 21. In which diagram does the current-carrying conductor experience a magnetic force out of the page? A) C) B) D) 22. The bar magnet below enters a solenoid from the left. What will be the direction of the induced current in the solenoid? A) A C) C B) B D) D 23. A student drops a bar magnet downward through a 1.0 m long plastic tube and then through a 1.0 m long copper tube of equal diameter. What will happen to the magnet in each situation? A) come to rest about halfway down each tube B) take longer to fall through the copper tube C) take longer to fall through the plastic tube D) take the same time to fall through each tube

6 24. The bar magnet below is pulled out of a solenoid as shown. Given the direction of the induced current in the solenoid, what will be the polarity of X and Y? X A) north north B) north south C) south north D) south south Y 25. A bar magnet is moved away from a coil as shown. What is the direction of the induced current through the resistor and the polarity of the left end of the coil? Polarity of left Direction of end of coil induced current A) X to Y north B) X to Y south C) Y to X north D) Y to X south 26. The diagram shows a bar magnet falling through an aluminum pipe. Electric currents are induced in the pipe immediately above and below the falling magnet. In which direction do these currents flow? ABOVE THE MAGNET BELOW THE MAGNET A) 1 3 B) 1 4 C) 2 3 D) The graph below shows the output from a generator. What is true of the generator? A) AC with multiple loops C) DC with multiple loops B) AC with a single loop D) DC with a single loop

7 28. As switch S is closed, in what direction does the compass needle point and what is the direction of the current through resistor R? COMPASS NEEDLE DIRECTION CURRENT DIRECTION THROUGH R A) west From 1 to 2 B) west From 2 to 1 C) east From 1 to 2 D) east From 2 to Two hollow-core solenoids, A and B, are connected by a wire, as shown in the diagram below. Two bar magnets, 1 and 2, are suspended just above the solenoids. What force will magnet 2 experience as magnet 1 falls through solenoid A? A) attraction by an electric force toward solenoid B B) attraction by a magnetic force toward solenoid B C) repulsion by an electric force away from solenoid B D) repulsion by a magnetic force away from solenoid B 30. The graph below shows the emf produced by a simple generator made with only one loop in thecoil and a permanent magnet producing the stationary field. What is the period of one rotation of the generator and does the generator have solid-slip rings or a split-ring commutator? PERIOD COMMUTATOR TYPE A) 0.05 s Solid slip ring B) 0.10 s Solid slip ring C) 0.05 s Split ring D) 0.10 s Split ring 31. Which device could be used to convert an AC generator to a DC generator? A) armature C) slip ring B) commutator D) transformer

8 32. Cell phones convert voice into electromagnetic impulses with a frequency range between 800 MHz to 2100 MHz. What is the wavelength of the most energetic electromagnetic waves transmitted by cell phones? A) 0.14 cm B) 0.38 cm C) 14 cm D) 38 cm 33. What is the main difference between a DC generator and an AC generator? A) A DC generator doesn't have any field magnets (permanent magnets) B) An AC generator doesn't have any brushes C) A DC generator doesn't have any brushes D) An AC generator doesn't have commutators 34. In the picture to the right the N pole of a magnet is being pulled out of the coil. Which of the next four pictures shows the correct illustration of the coil poles and the induced current in the coil? 35. In the diagram below, a permanent magnet is balanced above a coil of wire. When the switch is closed, the magnet is deflected upward. What is the magnetic polarity at the hollow core (X) and the charges at the battery terminal (Y)? 36. Which of the following factors does not affect the size of the induced current in a coil? A) number of turns in the coil B) size of the inducing field C) rate of change of the inducing field D) direction of the windings in the coil

9 37. Which of the statements below the picture is the correct one for the instant that the switch is closed in the primary circuit? A) the top of the secondary coil becomes a N pole and the induced current exits the top of the coil B) the top of the secondary coil becomes a S pole and the induced current exits the top of the coil C) the top of the secondary coil becomes a N pole and the induced current exits the bottom of the coil D) the top of the secondary coil becomes a S pole and the induced current exits the bottom of the coil 38. A coil is connected to a galvanometer. When a permanent magnet is held steady in the center of the coil, the galvanometer will indicate A) A steady current. B) A decreasing current. C) An alternating current. D) No current. 39. A charged particle is shot through a magnetic field as shown in each case below. Determine whether it will be deflected by the magnetic field and show the direction of the deflection. (i) negative particle (ii) positive particle 40. A charge of 1.5 x 10 6 C moves at 450 m/s along a path parallel to and 0.15 m away from a straight conductor. With a current of 1.5 A flowing in the same direction as the charge, what is the magnitude and direction of the force on the charge?

10 41. Calculate the magnitude and direction of the magnetic field strength at point P in the diagram provided. 42. An electric power transmission line has two wires 3.5 m apart that carry a current of 1.5 x 10 4 A. If the towers are 190 m apart, how much force does each conductor exert on the other between the towers? 43. An electron is shot perpendicularly into a 3.25 x 10-4 T magnetic field. If the electron moves in a circular path of radius 12.0 cm, calculate the speed of the electron. 44. A spacecraft orbiting Earth has a coil of wire in it. An astronaut measures a small current in the coil although there is no battery connected to it and there are no magnets on the spacecraft. Explain what causes the current. 45. The possible hazardous effects of exposure to electromagnetic waves such as radio frequency radiation from the antenna of a cell phone have yet to be determined. Describe two ways a cell phone user could reduce their risk of exposure to electromagnetic waves from the antenna.

11 46. Two people are talking to one another on their identical cell phones. Person A holds the phone 2.0 cm from his ear, while Person B holds it 6.0 cm from her ear. Explain which person will receive the greatest intensity of radio frequency radiation and state by what factor it is greater. 47. The diagram below shows a proton and an electron entering identical uniform magnetic fields of intensity T with the same initial speed of 1.4 x 10 5 m/s. A) What is the magnitude of the magnetic force on the electron? B) Sketch the shape of the path taken by the proton and electron after they enter the magnetic fields. 48. Faraday s ring shows two coils of insulated wire wrapped around an iron core, with a galvanometer in the bottom circuit. Use Lenz Law to predict the direction of the induced current in the bottom coil when the switch is closed. Explain your reasoning.

12 49. In the two situations below, a wire is pulled through a region with a given magnetic field as shown. Determine whether a current will be induced in the wire and show its direction. 50. Two identical magnets are dropped simultaneously through the hollow tubes as shown below. A student observes that both magnets fall at different rates. (a) Which magnet should fall faster? (b) Using your knowledge of physics principles, how could this observation be explained?

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