2 22. 1. 1. An ammeter is connected to a coil of wire An ammeter is connected to a coil of wire. A magnet is sitting motionless next to the wire such that its south end is near the coil and perpendicular to the plane of the coil as shown. The meter indicates that a current is flowing through the wire from the left toward the right. What, if anything, is wrong with this picture?a) The current should be flowingfrom the right toward the left.b) The needle should be slantedtoward the right.c) The needle should indicatethat there is no current flowing.d) There is nothing wrong with the picture.
3 Complete the following sentence: The phenomenon of producing an induced emf with the aid of a magnetic field isa) called electromotive production.b) almost never observed.c) a scientific curiosity with no practical application.d) only produced by changing the magnetic field in the presence of a coil of wire.e) called electromagnetic induction.
4 The plane of a conducting loop is oriented parallel to the x-y plane. A magnetic field is directed in the z direction. Which one of the following actions will not produce an induced emf in the loop?a) Decrease the area of the loop.b) Decrease the strength of the magnetic field.c) Increase the strength of the magnetic field.d) Rotate the loop about an axis that is directed in the z direction and that passes through the center of the loop.e) Rotate the loop about an axis that is directed in the y direction and that passes through the center of the loop.
5 22. 2. 1. A magnetic field is directed due north A magnetic field is directed due north. A vertical metal bar moving due east enters the magnetic field. Which one of the following phenomena is likely to occur?a) The bar will melt under the influence of the magnetic field.b) A motional emf will appear between the ends of the bar.c) The bar will become ferromagnetic.d) The bar will reduce the strength of the magnetic field on all sides of the bar.e) The bar will be accelerated by the magnetic field.
6 22.2.2. What is the origin of motional emf? a) moving electrons through a magnetic fieldb) changing magnetic field strengthc) changing direction of the magnetic fieldd) changing temperature conditions of a conductore) moving atomic nuclei through an electric field
7 A conducting bar slides with a velocity v to the right on some conducting rails as shown. A uniform magnetic field is directed perpendicular to the bar. Answer the following two questions: (1) Will the light bulb “turn on” in this case? and (2) How is the magnetic flux through the conducting loop changing, if at all, as the bar slides to the right?a) no, the magnetic flux remains constantb) no, the magnetic flux decreasesc) no, the magnetic flux increasesd) yes, the magnetic flux increasese) yes, the magnetic flux remains constant
8 22.3.2. Which of the following choices is the SI unit for magnetic flux? a) gauss (G)b) tesla (T)c) weber (Wb)d) Lumen (L)e) Fluxon (Fl)
9 22.3.3. Which of the flowing expressions equals the magnetic flux? a) BA cos b) (B cos2 ) / Ac) BA sin2 d)e) 0IBA
10 22.3.4. Which of the following phrases best describe the term magnetic flux? a) the direction of the magnetic field relative to a surfaceb) the amount of magnetic field that passes through a surfacec) the number of magnetic dipoles moving through a wired) the flow of magnetons in spacee) Choice (a) and (b) are both correct.
11 Consider the following physicists: (1) Michael Faraday, (2) Jean-Baptiste Biot, (3) Heinrich Lenz, (4) André Marie Ampère, and (5) Joseph Henry. Which of the men is(are) credited with the discovery of electromagnetic induction?a) 2 and 3b) 1 and 5c) 1 and 3d) 1 onlye) 3 only
12 A coil of wire with N turns and area A is placed into a magnetic field of magnitude B. The angle of the normal to the plane of the coil is at an angle with respect to the magnetic field. According the Faraday’s law, which of the following changes will produce an emf in a coil of wire?a) B is decreasedb) A is increasedc) is decreasedd) any of the above choicese) none of the above choices
13 One application of Faraday’s law can protect you from getting an electric shock. For example, if a wire breaks in your clothes dryer and touches the metal case, an electric current could pass through you to the ground. Which of the following devices could prevent you from being seriously injured in this scenario?a) synchrotronb) magnetronc) induction driverd) servo sensor coile) ground fault interrupter
14 Complete the following statement: Faraday’s law indicates that a changing magnetic field producesa) an electric field.b) an induced magnetic field.c) a force field.d) light.e) global warming.
15 Complete the following sentence: In a coil of wire, the direction of the induced current caused by an increasing magnetic flux isa) directed in the direction of the original magnetic field.b) directed opposite to the original magnetic field.c) such that the induced magnetic field decreases the magnetic flux.d) such that the net magnetic flux is equal to zero webers.e) such that the induced magnetic field increases the magnetic flux.
16 Which one of the following principle’s or laws allows one to determine the direction of an induced current in a conducting loop of wire due to a changing magnetic flux?a) Lenz’s lawb) Gauss’ lawc) equivalence principled) Faraday’s lawe) principle of induced magnetic flux
17 22.5.3. Lenz’s law is a consequence of what other physical law? a) Newton’s first lawb) conservation of energyc) Newton’s third lawd) conservation of momentume) Gauss’ law
18 Which of the following devices is not related to the reproduction of sound using electromagnetic induction?a) playback head of a tape deckb) microphonec) electric guitar pickupd) speaker
19 Complete the following statement by filling in the blank: An electric generator generates electrical energy from _____________________________, just the opposite of what a motor does.a) mechanical workb) electric potential energyc) gravitational potential energyd) thermal energye) electromagnetic energy
20 What type of electric generator results from a rotating planar coil of wire in a magnetic field?a) direct currentb) constant currentc) alternating currentd) constant emf
21 When a motor is turned on, its coil is initially not rotating. The startup current is observed to be larger than the current the motor draws when it is operating at normal speed. This observation can be explained by which of the following phenomena?a) The motor produces a back emf that increases with the speed of the motor.b) It takes a larger current to begin the rotation of the motor.c) The motor torque is initially very large, but small when it is operating at normal speed.d) The current drawn by the motor is inversely proportional to its operating speed.
22 22.7.4. Complete the following statement: Lenz’s law indicates that induced currents form to oppose a) a change in the magnetic field direction.b) a change in the magnetic field.c) the magnetic flux.d) a change in the electric flux.e) a change in the magnetic flux.
23 22.7.5. Which one of the following actions will not result in an induced current? a) Drop a magnet through a closed metal ring.b) Move a metal loop away from a current carrying wire.c) Drop an iron sheet through a region with a constant magnetic field.d) Hold a copper loop next to a current carrying wire.e) All of the above choices result in an induced current.
24 Which one of the following terms is used for the effect in which a changing current in one circuit induces an emf in another circuit?a) self-inductionb) coherencec) interferenced) Lenz effecte) mutual induction
25 22.8.2. What unit is used for inductance? a) weber (Wb)b) henry (H)c) ampere (A)d) morgan (M)e) volt (V)
26 An ac current is passed through a wire coil that is wrapped around an iron bar. The coil exhibits self-inductance. What is the name used for this coil?a) capacitorb) generatorc) amplifierd) inductore) collimator
27 In a well-designed transformer with an iron core, the secondary coil has twice as many turns as the primary coil. Which one of the following statements concerning this transformer is true?a) The flux that passes through each turn of the primary coil is twice the flux that passes through the secondary coil.b) The effect of the iron core is to reduce the magnetic field passing through the coils.c) The induced emf generated in the secondary coil is twice as large as that generated in the primary coil.d) This is a step down transformer because the current in the secondary coil is less than that in the primary coil.e) This kind of transformer is typically used between a power transmission line and a residence.