Physics II chapter 26 notes

Physics II chapter 26 notes - Chapter 26: Direct-Current...

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V6.01 RS/BQ S’10 67 Chapter 26: Direct-Current Circuits analysis of a circuit can often be simplified by replacing groups of resistors by a single resistor of equivalent resistance Resistors in Series and Parallel (26-1) For resistors in series same current flows through each resistor 123 II I I = = total voltage across set is sum of voltages across each to replace by single resistor, with equivalent resistance For resistors in parallel same voltage across each resistor ab V VV V = = total current through set is sum of currents through each to replace by single resistor, with equivalent resistance a b R R R R R 1 2 3 4 5 a b R R R R R 1 2 3 4 5 1 R V b I 3 R 2 R I a b V a V x position ( ) 11 2 2 33 1 2 3 ab V V I RI R I R I RR R =++ = + + = ++ eq ab V IR = eq 1 2 (series) R 3 12 111 ab I I V R V R  =   eq ab V I R = eq 1 2 (parallel) "reciprocal sum" 1 R
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V6.01 RS/BQ S’10 68 example : find current I drawn from power supply (having negligible internal resistance) and voltage 2 V across 2 R R 12 R 34 ε equivalent resistance current drawn is voltage 2 V across 2 R is the same as across 1 R , which is the same as the voltage across the single equivalent resistor which is many practical resistor networks (eg. bridge network) can not be reduced to simple series- parallel combinations (use Kirchhoff’s rules) 2 R 1 R 4 R 3 R a b 1234 R E + 12 34 14V 3.0 k 6.0 k 2.0 k 6.0 k RR = =Ω=Ω E ( ) ( ) 1234 12 34 1 2 3 4 (3)(6) (2)(6) k 3.5 k 36 26 R R R =+= +  = + Ω=  ++   1234 14V 4.0 mA 3.5k I R = = = E 12 1 2 2k R = = = + 1 R 2 R 3 R 4 R b R E + 2 12 (4.0mA)(2k ) 8.0V V IR = = 1 R 2 R 3 R 4 R E + I b
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V6.01 RS/BQ S’10 69 junction : a point in a circuit where 3 or more conductors meet Kirchhoff’s Rules (26-2) loop : any closed conducting path currents in arbitrarily complex circuit can be found from N linear equations in N unknowns using Kirchhoff’s two rules Kirchhoff’s junction rule algebraic sum of the currents into any junction is zero follows from charge conservation and requiring that
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This note was uploaded on 08/25/2011 for the course PHYSICS II 33-107 taught by Professor B.quinn during the Summer '10 term at Carnegie Mellon.

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Physics II chapter 26 notes - Chapter 26: Direct-Current...

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