Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley PowerPoint ® Lectures for University Physics, Twelfth Edition – Hugh D. Young and Roger A. Freedman Lectures by James Pazun Chapter 29 Electromagnetic Induction

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Goals for Chapter 29 To consider Faraday’s Law To consider Lenz’s Law To study motional emf To explore induced electric fields To summarize Maxwell’s equations and see their application to displacement current

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Introduction The motion of a magnet can induce current in practical ways. If a credit card has a magnet strip on its back, “swiping” the card can generate tiny currents that send information to cash registers. A coil of wire and magnets set into motion around each other will generate currents in the wire. A source of mechanical energy can drive the rotation and make a waterfall into an electrical power station.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Induced current Joseph Henry worked in the United States and Michael Faraday worked in England to discern the details of current generated in wire and permanent magnets in motion relative to each other. See Figure 29.1 below.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Knowing the magnetic flux Regardless of what moves, knowing the magnetic flux around a conducting entity will allow determination of current induced. See Figure 29.3 at right and Figure 29.4 below.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Emf and the current induced in a loop Follow Example Figure 29.5 illustrates the example.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Find the direction of an induced emf Consult Figure 29.6 and the text on the bottom of page 997 and top of page 998 and solve.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Faraday’s Law Follow Problem-Solving Strategy Refer to Example Figure 29.7 illustrates Example 29.2.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The search coil, generator example I Follow Conceptual Example Consider Example 29.4 and Figures 29.8 and 29.9.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Generator example II The example considers a DC generator and back emf in a motor.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Generator example III Follow Example Figure illustrates Example 29.6.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Work and power in a slidewire generator Follow Example Figure illustrates Example 29.7.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Lenz’s Law The direction of any magnetic induction effect is such as to oppose the cause of the effect. Follow Conceptual Example Follow Example 29.9; Figure illustrates the example.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley A conducting rod moving in a uniform magnetic field The rod, velocity, and current are mutually perpendicular. See the direction of the induced current in the circuit below. Follow Example

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The Faraday Disk dynamo Follow Example Figure illustrates Example

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Induced electric fields I The windings of a long solenoid carrying a current I

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Induced electric fields II Refer to Figure below. Follow Example

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Eddy currents Consider Figure at right. Consider Figure below.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Displacement current and Maxwell’s equations A varying electric field will give rise to a magnetic field. Explains electromagnetic waves.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Superconductivity and the Meissner effect When cooled below the critical temperature, superconductive materials lose all resistance to electrical current. Refer to Figures and at right.