Gauss’s LawWhat’s Happening Dude?Electric Field LinesWhere is the Electric Field The Strongest?Field LinesLast timeSmall AreaAmbiguityThe ambiguity is lost ifThe ins and outs of it …..Slide 11Complete Pages 6-8 in the Unit Copy your chart to a whiteboard when you are finished. Then continue through page 9.Slide 13NEW CONCEPTSlide 15Slide 16What is so important about FLUX??Slide 18Slide 19May the flux be with you.W4D2Today Gauss’s Law is happening. Big time.There is a new WebAssign, don’t cha know?There is one of those Quiz thingys on Friday.You have to download the next unit for Friday and you should look at the website.Electric Field LinesElectric Field LinesWhich charge is bigger?A The (+) chargeB The (-) chargeC They are the sameD You can’t tellWhere is the Electric Field Where is the Electric Field The Strongest?The Strongest?ABCDField LinesField LinesThe number of lines leaving (or entering) a charge is propositional to the chargeThe electric field at a place in space is proportional to the density of the lines.You can use a small area oriented perpendicular to the electric field to probe the strength of the field by counting the lines that pass through the area.We will define the FLUX (F) passing through the area as proportional to the number of lines passing through this area multiplied by the area.fluxLast timeLast timeWe can use a vector to represent a small flat area:◦It’s length is proportional to the area.◦Its direction is perpendicular to the area◦The area need not be square, round or anything else. It must be small. Very small. Teeny Tiny small.There is an ambiguity in which of two ways the vector can point for a particular small area.Small AreaSmall AreaSmall AreaAmbiguityAmbiguityWhich One??The ambiguity is lost ifThe ambiguity is lost ifA. We change the definition to include up and down.B. We apply the definition to a closed surface.C.We only use the vector that is un-obscured by the surface as we look at it.D.We really can’t deal with this in an undergraduate course.The ins and outs of it …..The ins and outs of it …..PositiveLeaving the VolumeNegativeEntering the VolumeClosed VolumeClosedWe represent a surface as the area surrounded by a perimeter that we will call a “loop”. The loop defines the boundary of the area. The boundary of the shaded area below is the loop defined above.Complete Pages 6-8 in the Complete Pages 6-8 in the UnitUnitCopy your chart to a Copy your chart to a whiteboard when you are whiteboard when you are finished.finished.Then continue through page Then continue through page 9.9.cosEAThe electric flux through a surface is defined as the magnitude of the electric field times the area of the surface times the cosine of the angle between the direction of the electric field and the area vector of surfaceThe units of flux are Nm2/C. Qualitatively; flux is the number of field lines passing through a surface. When the angle between the area vector of the surface and the direction of the electric field is greater than 90, the flux is negative. =Normal Component of E X ANEW CONCEPTNEW CONCEPTWhat is so important about What is so important about FLUX??FLUX??CLOSED SurfaceOUTWARD Pointing Normal22200( )(4 )44i iiE AE A EA E Rq qRRppepeF = F = DF = D = =F = =� ��Gauss’s LawGauss’s LawGaussian SurfaceGauss’s LawGauss’s Law0TOTAL FLUXEnclosed ChargeLEAVING ANYCLOSED VOLUMETotal ie� �� �=F = F =� �� �� ��His Law!May the flux be with you.May the flux be with
View Full Document
Unlocking...