Phys 202 1nd Edition Lecture 8Outline of Last Lecture I. Circuits and Ohms lawOutline of Current Lecture II. CircuitsIII. Capacitors in SeriesIV. Resistors in ParallelCurrent LectureCircuits:Ohms law stats that the potential difference in a circuit is equal to the resistance times the current through the circuit (V=IR). Capacitors in a circuit follows a similar rule. In a circuit with capcaitors, the charge is equal to the potential difference times the capacitance (Q=VC or V=Q/C). The positions of resistors or capacitors in a circuit (parallel vs. being in series).Capacitors in series: C2 EIn series, the capacitors will be right next to one another. The sum of two capacitors in series is equal to the reciprocal of the sum of the reciprocals of the two capacitance. Veq=Q/CeqVeq=V1+V2V1=Q/C1V2=Q/C2These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. C1Q/Ceq= Q/C1 + Q/C21/Ceq=1/C1 + 1/C2Ceq=C1C2/C1+C2Since Ceq is based on the reciprocal of the capacitance, Ceq will be smaller than both C1 and/or C2When capacitors are connected in series, they will always have the same charge, but different potential, and therefore different capacitance.Resisters in series:When you have a circuit with two or more resisters in series, the resistance of the whole system (Req) is simply equal to the sum of resistance of the resistors.Veq=ReqIReq=R1+R2V1=R1IV2=R2IVeq=V1+V2Veq=I(R1+R2)Circuits in parallel: E= R2 When circuits are in parallel, the rules for the value of the resistance are the same as the rules of capacitors when they are in series. E/Req=E/R1+E/R21/Req=1/R1+1/R2Req=R1R2/R1+R2R1Proportionality: If R1=5 and R2=10 and the two charges are in parallel, then the current passing through R1 will be twice as large as the current flowing through R2.Capacitors in parallel follow the same rules as resistors do in series (Ceq=C1+C2)Examples: E=6V R3=200 R1=480 R4=140R1 is parallel to R2R1 and R2 is in series with R3 and R4 R12=R1R2/R1+R2Req=R12+R3+R4I=E/Req=6/640=.009375Veq=IReq=6 C3=11µF C1=3µF E=22VQeq=VCeqC12=C1+C2=11.5µFC123(or Ceq)=C12C3/(C12+C3)=5.62µFR2=800C2=8.5Q123=VC123=22*.00000562C
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