# r1 r2 r3 r3 v i1234 r1234 r4

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Unformatted text preview: drop across is IRi Reffective = R1 + R2 + R3 + ... Resistors in parallel: 1 Voltage drop across is same. Reffective Current through is V/Ri Solved Circuits R2 R1 V 11 1 = + + + ... R1 R2 R3 = R3 V I1234 R1234 R4 Physics 212 Lecture 10, Slide 5 Physics 212 Lecture 10, Slide 5 Last Time Physics 212 Lecture 10, Slide 6 Physics 212 Lecture 10, Slide 5 New Circuit R1 R3 V1 V2 R2 How Can We Solve This One? R1 V1 V2 R3 R2 = V I1234 R12 THE ANSWER: Kirchhoff’s Rules Physics 212 Lecture 10, Slide 7 Physics 212 Lecture 10, Slide 5 Kirchoff’s Voltage Rule ∑ ∆V i =0 Kirchoff's Voltage Rule states that the sum of the voltage changes caused by any elements (like wires, batteries, and resistors) around a circuit must be zero. WHY? The potential difference between a point and itself is zero ! Physics 212 Lecture 10, Slide 8 Physics 212 Lecture 10, Slide Kirchoff’s Current Rule ∑I in = ∑ I out Kirchoff's Current Rule states that the sum of all currents Kirchoff's entering any given point in a circuit must equal the sum of all currents leaving the same point. WHY? Electric Charge is Conserved Physics 212 Lecture 10, Slide 9 Physics 212 Lecture 10, Slide Checkpoint 1 How many potentially different currents are there in the circuit shown? A. 3 B. 4 C. 5 D. 6 E. 7 “two for the parallel branch and then one for the first two and last resistors .” and A “There are four different series connections” B C “there is D there potentially one between every pair of resistors.” resistors.” Physics 212 Lecture 10, Slide 10 Physics 212 Lecture 10, Slide Checkpoint 1 How many potentially different currents are there in the circuit shown? I1 I3 I2 I1 A. 3 B. 4 C. 5 I3 D. 6 E. 7 Look at the nodes! Top node: A B Bottom node: C D I1 flows in, I2 and I3 flow out I2 and I3 flow in, I1 flows out That’s all of them! Physics 212 Lecture 10, Slide 11 Checkpoint 2 In the following circuit, consider the loop abc. The direction of the cu...
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## This note was uploaded on 02/18/2013 for the course PHYS 212 taught by Professor Kim during the Fall '08 term at University of Illinois, Urbana Champaign.

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