Chapter 22 – Alternating Current Part 1Upcoming items for your considerationExam STructureSlide 4OK … How was the test?How did you do?This time I didac generator“Output” from the previous diagramSlide 10NuclearDC /AChome generatorswhat works on ac?Slide 15But not always! (capacitor)Let’s talk about phase y=f(x)=x2y=f(x-2)=(x-2)2the “rule”The SineLet’s talk about PHASEFor the futureAC Applied voltagesphasoroops – the ac phaserthe resistorPhasor diagramhere comes trouble ….From the last chapter:check it out---so-Slide 32this leavesresultcomparingslightly confusing pointback to the phasor thingWhat about the capacitor??capacitor phasor diagramNOTICE THATSUMMARYPHY-2054J. B. BindellNo problem session on Monday (Not much to do!)Watch for a Mastering Physics AssignmentQuiz next Friday on AC … will it ever end?Today we start AC CircuitsWe will review the exam when they are returned.Question Number Section 003 Section 0041 Multiple Choice (5) Multiple Choice (5)2 (seen before) 2-Wire Problem – Different currents in each class and different from the quiz2-Wire Problem – Different currents in each class and different from the quiz3 (similar or exactly from past.)Inverted coil problem. Coil problem from class.4 (New) Charged particle orbit. Electron & proton in same orbit.PHY2054 Problem Solving/Office Hours ScheduleRoom MAP-318Monday Tuesday Wednesday Thursday FridayBindell 8:30-9:15AM 8:30-9:15AM 8:30-9:15AMBindell 11:00-12:00PM10:30 - 11:15 AM* 10:30-11:30AMDubey 12:00-1:00PM 1:30-2:45PM These sessions will be used both for office hours and problem solving. Students from anysection of 2054 are invited to stop by for assistance in course materials (problems, etc.)Note: There will be times when the room may not be available. In that case we will use our individual offices. * In Office Dr. Dubey's hours are for problem solving only.If something else is going on in the room, come to my office!If I am not there …. come to my office.We will retain this schedule.A. EasyB. OKC. DifficultD. ImpossibleA. greatB. less than stellarC. okD. poorE. bombedA. better than last timeB. about the same as last timeC. worse than last time2FUELx2(x-2)2yx2f(x-b) shift a distance b in the POSITIVE directionf(x+b) shift a distance n in the NEGATIVE direction.The signs switchswitch!2f(t)=A sin(t)A=Amplitude (=1 here)f(t)=A sin(t-[/2])A=Amplitude (=1 here))cos()2sin( ttftttt2)sin()2cos()cos()2sin(This graph correspondsto an applied voltageof V cos(t).Because the currentand the voltage aretogether (in-phase) thismust apply to a Resistorfor which Ohmmmm saidthat I~V.)cos( tIi)cos( tIRiRvIRVRPretty Simple, Huh??We need the relationship between I (the current through)and vL (the voltage across) the inductor.tiLvL* unless you have taken calculus.initialfinalinitialfinal tt(t) thingthing(thing).differenceor change means ttttttLILvttttILttILtiLLv)cos()sin()sin()cos()cos())cos()(cos()cos(Whent gets very small,cos (t) goes to 1.canceltttLIvL)sin()sin(:left sat what'look sLet'??r1)sin(lim0)sin( tvLThe resistor voltage looked like a cosine so we would like theinductor voltage to look as similar to this as possible. So let’slook at the following graph again (~10 slides back):f(t)=A sin(t)A=Amplitude (=1 here)f(t)=A sin(t-[/2])A=Amplitude (=1 here))cos()2sin( tt)cos()2sin( tt)sin( tLIvL)2cos()2cos()sin(tLIvttLRESISTOR INDUCTOR)cos( tIRiRv)2cos( tLIvL RIvR max LIvMaxLL) looks like a resistanceXL=LReactance - OHMSWe will use the CURRENT as the basis for calculations and express voltages with respect to the current. What that means? voltage. theandcurrent ebetween thshift phase theis where)tVcos(vas voltage theandt)cos( Ii:as varyingascurrent thedescribe We)cos(111:tIcictqctvcqvCccWithout repeating what we did, the question is what function will havea f/t = cosine? Obviously, the sine! So, using the same processthat we used for the inductor,(ohms) 1 )sin(1CXtICvcc)2cos(v(ohms) 1 )sin(1CtCICXtICvccThe voltage lags the current by 90 degI and V are represented on the same graph but are different
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