Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley PowerPoint Lectures for College Physics, Eighth Edition Hugh D. Young and Robert M. Geller Lectures by James L. Pazun Chapter 21 Electromagnetic Induction

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Goals for Chapter 21 To overview electromagnetic induction and Faraday’s Law. To observe examples of Lenz’s Law. To study motional electromotive force. To understand eddy currents. To study and calculate mutual and self inductance. To understand and calculate the action of transformers. To study and calculate magnetic field energy. To study R-L and L-C circuits.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Does the field induce a current or not? – Figure 21.1 In each situation, discuss why a current would be produced or not.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Investigating induced currents – Figure 21.2 Changes in the magnetic field or the coil will be detected on the multimeter.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Magnetic flux through an area – Figure 21.3 Recall back to Chapter 17 and Gauss’s Law. See Conceptual Analysis 21.1 and Example 21.1.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Magnetic flux at various orientations – Figure 21.4 The flux depends on angle of the sample surface. Refer to Conceptual Analysis 21.1 and Example 21.1.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Faraday’s Law – Figure 21.7 The induced current is proportional to the time and the field strength Refer to Example 21.3, Conceptual Analysis 21.2 and Problem Solving Strategy 21.1 in your text.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley You can induce emf in a coil of wire – Figures 21.9,10 This progression of ideas regarding the creation of induced emf in moving conductors leads to the simple alternator.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Lenz’s Law – Figure To derive the direction as well as the magnitude of an induced field, Lenz expanded on Faraday’s Law. Notice that it follows the right hand rule.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Force on a slide wire rod – Figure The movement of the rod implies a force. Refer to example 21.5 in your text.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley The same principle in a R-C circuit – Figure Refer to worked example 21.6 in your text.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Motional Electromotive Force – Figures 21.18, 19 Refer to worked example 21.7 and Conceptual Analysis 21.3.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Eddy currents – Figure So far, the magnetism we have studied in circuits was well-defined. This organized behavior is the norm in circuits and along wires. Like the rotating disk in an electric meter outside your home, swirling patterns of induced currents occur at specific regions and allow for a net force to occur.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Eddy currents II – Figure Metal detectors depend on the eddy currents that a concealed weapon could produce.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Mutual inductance – Figures on page 712 Circulation of powerful currents generate a field in one device that will induce a current in a separate device.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley The Tesla Coil – Figure Mutual induction is applied to allow two sets of wire turns, one long and one smaller, to transform voltages. Refer to Examples 21.8 and 21.9 in your text.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Self-inductance – Figures 21.24,25,26 Any circuit which carries a varying current self- induced from it’s own magnetic field. Refer to worked example in your text.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Transformers – Figures on page 717 Two coils are wound on the same core. One coil will generate a field in the core which induces a current in the second coil.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Transformers II – Figure Refer to worked example in your text.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley Energy associated with an induced current. As energy is introduced at induces a field, energy is stored in an electronic device. Refer to worked example in your text.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley The R-L circuit – Figure When an inductor is part of a wired circuit, - voltages, currents and capacitor charges are a function of time, not constants. Refer to worked example in your text.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley The L-C circuit – Figure When an inductor is part of a wired circuit with a capacitor, the capacitor charges over time. Commonly used in radio as a tuner for the induced current from an antenna.