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DISCUSSION SESION 2

DISCUSSION SESION 2. EQUESTIONS 2: ENERGY CONSERVATION PRINCIPLE. OBJECTIVES. CURRENT FLOW REFERENCE/MEASUREMENT VOLTAGE POLARITY REFERENCE/MEASUREMENT PASSIVE SIGN CONVENTION/ (DELIVERED/ABSORBED) POWER ENERGY CONSERVATION. CURRENT FLOW REFERENCE/AMMETER CONNECTION.

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DISCUSSION SESION 2

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  1. DISCUSSION SESION 2 EQUESTIONS 2: ENERGY CONSERVATION PRINCIPLE Ertuğrul Eriş

  2. OBJECTIVES • CURRENT FLOW REFERENCE/MEASUREMENT • VOLTAGE POLARITY REFERENCE/MEASUREMENT • PASSIVE SIGN CONVENTION/ (DELIVERED/ABSORBED) POWER • ENERGY CONSERVATION Ertuğrul Eriş

  3. CURRENT FLOW REFERENCE/AMMETER CONNECTION Chosen currunt flow reference/Calculation results/Ammeter connection What happens if current flow reference is chosen randomly? Ertuğrul Eriş

  4. VOLTAGE POLARITY REFERENCE/VOLTMETER CONNECTION Chosen voltage polarity reference/Calculation results/voltmeter connection What happens if voltage polarity reference is chosen randomly? Ertuğrul Eriş

  5. PASSIVE SIGN CONVENTION • Problem: How could we differentiate whether an element deliver energy or absorb energy? • Possible answer could be the sign of the power value! How decide? Chages by references • Passive sign convention (PSC) rule:voltage (+) polarity reference is at the beginning of the current flow arrow • P=v.i under the condition of PSC • RESULT1: ALWAYS THE SAME DECISION • RESULT2: One reference is enough Ertuğrul Eriş

  6. PASSIVE SIGN CONVENTION + - - + - + - + Va, ia V, i Va, ia V, • RULE: Passive sign convention (PSC) : • voltage (+) polarity reference is • at the beginning of the • current flow arrow • Definition: Power=va*ia • under the condition PSC • Pa=va*ia P=v*i=-va*-ia=Pa • Pa>0 absorbing power • Pa<0 delivering power • Always the same decision! Could have been an alternatif, But the other one accepted! Ertuğrul Eriş

  7. ENERGY CONSERVATION • Electrical energy absorbed by a resistor has gone where? • Where is energy conservation? Ertuğrul Eriş

  8. QUESTIONS • Which components power is negative? What’s the meaning of negative power? • Which components power is positive? What’s the meaning of positive power? • Depending on voltmeter/ammeter terminal connection to the components, you might find different signed voltage and currents values for the same component. This causes different signed power values for the same components therefore we cannot state whether components generate or absorb power. What is your solution to this chaos? • Is components’ powers sum equal to zero? Why? • Resistors covert electrical energy to what type of energy?1 • What might be error source for the theoretical and measured results? • What is passive sign convention? • Why independent KVL and KCL equations we used? What happens if dependent euqations are used? Ertuğrul Eriş

  9. PROBABLE SOURCES OF FALSE MEASUREMENTS • Internal resistances of measurement instruments • Elements values tolerances • Reading mistakes • How to avoid these falses!! Ertuğrul Eriş

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