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 22 Gauss’s Law

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Goals for Chapter 22 To study electric flux To calculate electric flux with Gauss’s Law To consider the electric field of various symmetric charge distributions

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Introduction The movement of electrons can be shocking (pardon the pun). If you look at the girl’s hair (figure to the right), you’ll see the electrons coating each individual hair fiber and then repelling each other. Gauss imagined a flow through a surface placed around a charge and then considered outcomes that we will study in Chapter 22.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Flux as the flow out of an imagined box If we construct a boundary around a charge or charges, we can think of the flow coming out from the charge like water through a screen surrounding a sprinkler.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley What happens as I change the conditions? Consider +1 versus +2 or a box with double the containment dimension.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley A measurement of flux will be sensitive to measurement If we considered flux through a rectangle, the flux will change as the rectangle changes orientation to the flow.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Flux in a uniform field Measurement of the flux for a uniform electric field

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley If the field is not uniform—the disk Refer to Example 22.1 to evaluate flux through a disk. Figure 22.7 illustrates this example.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley If the field is not uniform—the cube Refer to Example 22.2 to evaluate flux through a disk. Figure 22.8 illustrates this example.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley If the field is not uniform—the sphere Refer to Example 22.3 to evaluate flux through a disk. Figure 22.9 illustrates this example.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Gauss’s Law The expression is an alternative to Coulomb’s Law. The nifty thing about being a scientist in Gauss’s day is that you got to leave your name on clever work (not to mention the nice painting).

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Flux through concentric spheres with different radii Consider the flux as changing the radius of the sphere changes its volume.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Projecting flux through other shapes Consider Figure to contemplate flux through nonspherical surfaces.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Effect of changing the sign of the charge Figure leads us to consider the effect of changing the sign of our point charge.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley There are practical applications Figure treats excess charge as residing on the surface of a conductor. Consider Example Figure illustrates Example 22.5.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The field of a line or plane of charge Consider Example 22.6 and Figure See also Example 22.7 and Figure

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley A field between parallel plates of opposing charge The capacitor is the actual device.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The field of a uniformly charged sphere Consider Example Figure illustrates the example. Follow Example

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Charges on conductors The electric field within a charged conductor may be found. Consider Figure Follow Example and Figure

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Experimental tests of Gauss’s Law Regard Figure A metal container on an insulating stand.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The Van de Graaff generator The source of all the static on the child’s hair in our introduction. Consider Figure below.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley A Faraday cage blocks flow Refer to Figure below. Science-fiction movies always place alien transmitters in these to prevent them from calling for help. Follow Examples and