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# Ch 11 - kirchoff's laws ppt

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Power point is done with an additional student note sheet and power point is projected on whiteboard and circuits are written on.

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• Show on white board instead of screen and loops can be drawn in with class. Class will have multiple circuits so they can take notes.
• Use diagram projected on white board to label currents with students.
• Use white board to get equations with students based on their chosen current labels.
• Show students on white board how the possibilities are. Recommend to go out of positive.
• Show students on white board how to obtain equations.
• Show students on white board how to obtain all the equations.
• ### Ch 11 - kirchoff's laws ppt

1. 1. Kirchoff’s RulesPurpose: solve complex circuits
2. 2. Some terminology• Loop: ANY closed 5Ω 12 V path in a circuit. This one has three loops. The loop direction is 10 Ω arbitrary.Best practice: follow out of the + side of battery when 20 Ω 6V possible.Junction: where two or more wires meet.
3. 3. Purpose of Rules:• Since some circuits are too complex they must be solved using Kirchoff’s Rules. These rules follow the principle and ideals of conservation of charge and conservation of energy. The rules help keep track of +/- for potentials.
4. 4. Before applying rules, label currents in loopsChoose current directions. 5Ω 12 V Use arrows right on the wire to indicate current and label with I1 I2, and/or 10 Ω I3.Cannot have all three currents enter or leave a junction simultaneously. At least one direction 20 Ω 6V must be different coming in or out of a junction.
5. 5. 1. Junction Rule• At any junction the sum of all currents entering must equal the sum of all currents leaving the 5Ω 12 V junction. This is conservation 10 ΩOf charge.Equations: 20 Ω 6V
6. 6. Loop Rule• The sum of the changes in potential 12 V 5Ω around any closed path of a circuit must be zero. 10 ΩThis is conservation of energy. 20 Ω 6V
7. 7. Voltage: + or - ???• When tracing a current 5Ω 12 V through a loop, start at a battery.The V will be + when you 10 Ω trace neg to pos. (uphill)The V will be – when you trace pos to neg. 20 Ω 6V (downhill)
8. 8. IR values through resistors• Apply Ohms Law: 5Ω 12 V V = IR IR will be neg when direction of loop and 10 Ω current match.IR will be pos when loop trace goes against 20 Ω 6V current
9. 9. The idea is to get all the equations and the correct signs 5Ω 12 V• Apply junction rule for current equation 10 Ω• Apply loop rule and sign protocol for IR and battery voltages 20 Ω 6V
10. 10. The idea is to get all the equations and the correct signs 5Ω 12 V• Apply junction rule for current equation 10 Ω• Apply loop rule and sign protocol for IR and battery voltages 20 Ω 6V