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Unformatted text preview: Direct Current Circuits Chapter 28 All sections except 5 28.1 Electromotive Force 28.2 Resistors in Series and Parallel 28.3 Kirchhoffs Rules 28.4 RC Circuits PHYS142 Lecture 15 1 Kirchhoffs Rules (28.3) 1. Junction/Node Rule The sum of the currents entering a junction equals the sum of the currents leaving that junction junction I 1 I 2 I I = I 1 + I 2 Conservation of charge 2 2. Loop Rule The algebraic sum of the changes in potential around any loop must be zero. * The potential increases for a path from the terminal to the + terminal of a battery. * The current flows from a higher potential to a lower potential. Conservation of energy 3 + V _ + V R R path path path path Decrease in potential, V Increase in potential, +V Decrease in potential, IR Increase in potential, +IR I I 4 _ I I I + _ A B C Loop: A B C A V A B + V B C + V C A = 0 + V I R 2 I R 1 = 0 R 2 R 1 Example 3: 5 2 1 R R V I V In the circuit below, all the resistors have equal resistance. Rank the electric potentials at points a, b, c, d , and e from highest to lowest, noting any cases of equality in the ranking. Question 1 1 2 3 4 4% 12% 11% 73% 1. b > c > a = e > d 2. a > d > b = c > e 3. e > a = b > c = d 4. a= d > b = c > e Example 3 Find the current in each resistor in the figure below. 5 1 R 60 2 R 30 3 R 100 4 R 40 5 R V 12 7 R and R 1 are connected in series; 1 R R R 25 5 1 R 20 R 1 0 0 4 R 4 0 5 R V 12 8 Example 3 R...
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This note was uploaded on 02/22/2011 for the course PHYS 142 taught by Professor Altounian during the Spring '07 term at McGill.
 Spring '07
 ALTOUNIAN
 Current, Magnetism, RC Circuits, Force

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