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PreAP : Circuits

PreAP : Circuits. Circuit Design. Circuits can use all of the following: Circuits must be a closed path for electrons to travel from one end of the battery to the other. Drawing Circuits. Always Start from the positive terminal on the battery and draw thru the rest back to the negative end

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PreAP : Circuits

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  1. PreAP: Circuits

  2. Circuit Design • Circuits can use all of the following: • Circuits must be a closed path for electrons to travel from one end of the battery to the other

  3. Drawing Circuits • Always Start from the positive terminal on the battery and draw thru the rest back to the negative end • Use Conventional Current

  4. Series Circuit • Electrons can only move down one path: • Electron never has choice

  5. Resistance in Series • The total resistance of the circuit can be determined for series circuits from Rs = R1 + R2 + ……RN

  6. Examples • Load #1 and #2 both have resistance of 5 ohms. Determine the equivalent resistance • The lightbulbs have resistances of 25, 50 and 100 Ohms respectively. Determine equivalent resistance

  7. Resistors in Series The total current remains the same throughout the entire circuit The voltage varies throughout the circuit and starts at the EMF value and ends at zero

  8. Resistors in Series A metal slider moves along the resistor dividing the resistor into a series combination. The difference in voltage is detected at the slider and sent to computer

  9. Parallel Circuits • Where electrons have a choice in what path they take • Where do electrons have choice?

  10. Resistance in Parallel • The total resistance of the circuit can be determined for series circuits from (1/Rp) = (1/R1 ) + (1/R2 ) + ……(1/RN) Wires in parallel have same voltage with different resistances and currents

  11. Examples • Each of the following resistors has a resistance of 5 ohms Determine the total resistance • The resistors have values of 5, 10 and 20 Ohms respectively determine equivalent resistance

  12. Parallel Branches At the junction or point where the branches split Voltage is the same in each branch Current splits with the sum of the current equal to the current coming in

  13. Solving Combined Circuits

  14. Circuit Problems Problem Solving • Combine all resistors in series • Combine all resistors in parallel • Repeat # 1-2 until one equivalent resistance found • Determine the current/voltage of circuit • Determine current or voltage at specific points REDRAW CIRCUIT AT EVERY STEP

  15. Problem Solving • Put 4 and 6 Ohms together • Put both 10 Ohm resistors in parallel together

  16. Equivalent Resistance • Put all three resistors in series together 3) Total Resistance becomes 25 Ohms

  17. Current 4) Determine current using Ohms Law 5) Determine voltage and current after each resistor.

  18. Internal Resistance The resistance in the source of voltage due to the chemicals or wires in the voltage source Signified by r

  19. Kirchhoff's Rules Used for circuits in which no two circuits are in parallel or in series Junction Rule Loop Rule

  20. Junction Rule Application of Conservation of Charge Total current into a junction must equal total current coming our of junction

  21. Loop Rule Application of Conservation of Energy Around any closed loop sum of potential drops equals sum of potential rises

  22. Example Determine the current in the circuit

  23. Measuring Current Ammeter Essentially zero resistance Inserted in Series

  24. Measuring Voltage Voltmeter Have large resistance to draw away current Must be wired in parallel

  25. Capacitors in Parallel Because voltage is the same in each branch q = q1 + q2 = C1V +C2V = CpV so Cp = C1 + C2 + ……

  26. Capacitors in Series All capacitors in series have the same magnitude of charge but the voltage varies leading to 1/Cs = (1/C1) + (1/C2) +...

  27. RC Circuits Circuits that have both resistors and capacitors Use the time to charge and discharge a capacitor for timing functions

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