Physics 213 General PhysicsPowerPoint PresentationSlide 3Slide 4Circuit Analysis -- Kirchhoff’s RulesJunction RuleLoop RuleSlide 8More About the Loop RuleSlide 10Slide 11Slide 12Slide 13Slide 14Slide 15TextSlide 17Slide 18Slide 19Physics 213General PhysicsLecture 62Last Meeting: Current, Resistance, and Power Today: Resistor Networks, Direct-Current Circuits3VOLTUnit: OHM=AMPERE4Circuit Analysis -- Kirchhoff’s RulesJunction RuleThe sum of the currents entering any junction must equal the sum of the currents leaving that junctionLoop RuleThe sum of the potential differences around any closed loop is zeroI1 = I2 + I3Junction RuleI1 = I2 + I3From Conservation of ChargeDiagram b shows a mechanical analogLoop RuleAssign symbols and directions to the currents in all branches of the circuitIf the direction of a current is incorrect, the answer will be negative, but have the correct magnitudeChoose a direction to transverse the loopsRecord voltage rises and drops00221122RIRIRIVTwo equations from loop rule21III One equation from junction ruleLoop RuleAssign symbols and directions to the currents in all branches of the circuitIf the direction of a current is incorrect, the answer will be negative, but have the correct magnitudeChoose a direction to transverse the loopsRecord voltage rises and dropsAlternate loops could be used.For this example -- still only gives three equations. Can be used to solve for three unknowns in this example.Generally, the number of different equations from both rules allows you to solve that many unknowns.More About the Loop RuleTraveling around the loop from a to bIn a, the resistor is transversed in the direction of the current, the potential across the resistor is –IRIn b, the resistor is transversed in the direction opposite of the current, the potential across the resistor is +IRIn c, the source of emf is transversed in the direction of the emf (from – to +), the change in the electric potential is +εIn d, the source of emf is transversed in the direction opposite of the emf (from + to -), the change in the electric potential is -εMore About the Loop Rule1112Demo Light bulb tree131415Text161. Increases2. Decreases3. Stays the
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