1 / 15

Agenda

Agenda. Today Finish Chapter 26: RC Circuits Freedom? Post-Freedom Magnetism & Induction: 27-29 Post-Post Freedom Finish induction & Review, Exam II. Capacitors in Circuits. Series 1/C T = 1/C 1 + 1/C 2 … Effective Distance increased, reduces C T Parallel C T = C1 + C2 + C3…

caldwell-dunlap
Download Presentation

Agenda

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Agenda • Today • Finish Chapter 26: RC Circuits • Freedom? • Post-Freedom • Magnetism & Induction: 27-29 • Post-Post Freedom • Finish induction & Review, Exam II

  2. Capacitors in Circuits • Series • 1/CT = 1/C1 + 1/C2 … • Effective Distance increased, reduces CT • Parallel • CT = C1 + C2 + C3… • Effective Area increased, increases CT • Effectively opposite of Resistors • What is voltage dependence for R’s? • Current • What is voltage dependence for C’S? • Charge • I = dQ/dt ….

  3. What Happens Here? Start with Switch Open? Close Switch Lamp + -

  4. What Happens Here? Start with Switch Open? Close Switch What occurs now? Changes with Time? At t=0, cap’s are shorts Filling with charge, no opposition to flow At t= infinity, cap’s are opens Filled with charge After a long time…. Lamp + -

  5. What Happens Here? Start with Switch Open? Close Switch What occurs now? Changes with Time? At t=0, cap’s are shorts Filling with charge, no opposition to flow At t= infinity, cap’s are opens Filled with charge After a long time…. Voltage on Capacitor = Voltage of Cell No current flow, Lamp is off Now take out battery, replace with switch Lamp + + - -

  6. What Happens Here? What Happens when switch is closed? Path emerges for charge to flow Light back on for some time Dims, then off as charge dissipates Lamp + -

  7. Discharge Circuit Capacitor Begins with Voltage V Q=VC Lamp = Resistor value R Assume constant R for simplicity Define states: Initial & Final Initial (t=0) switch JUST closed Final (t=infinity) looong time after Initial, Current max or min? Max Final, Current max or min? Min (zero) Now we have “boundary values” Next up: DiffEQ Lamp + -

  8. Discharge Circuit Q=VC Initial: VC = V, I=I0 Final: VC = 0, I = 0 Examine Voltage Loop VC + IR = 0 R Lamp resistance Holds true for any time Q/C = -IR Q/C = -R(dQ/dt) -(Q/C)dt = RdQ -dt/(RC) = dQ/Q Integrate Both Sides (tau) = RC [Time Constant] Lamp + -

  9. Discharge Circuit Q=VC Initial: VC = V, I=I0, q = Q0 Final: VC = 0, I = 0, q = 0 -dt/(RC) = dQ/Q Integrate Both Sides (tau) = RC [Time Constant] Lamp + - Book does same by choosing integration limits Here: Use constants to match boundary conditions

  10. Discharge Circuit Q=VC Initial: VC = V, I=I0, q = Q0 Final: VC = 0, I = 0, q = 0 -dt/(RC) = dQ/Q Integrate Both Sides (tau) = RC [Time Constant] Lamp + - What should A be?

  11. Discharge Circuit Q=VC Initial: VC = V, I=I0, q = Q0 Final: VC = 0, I = 0, q = 0 -dt/(RC) = dQ/Q Integrate Both Sides (tau) = RC [Time Constant] Lamp + - Charge not usually too useful Voltage?

  12. Discharge Circuit Q=VC Initial: VC = V, I=I0, q = Q0 Final: VC = 0, I = 0, q = 0 -dt/(RC) = dQ/Q Integrate Both Sides (tau) = RC [Time Constant] Lamp + - Charge not usually too useful Voltage?

  13. Discharge Circuit Q=VC Initial: VC = V, I=I0, q = Q0 Final: VC = 0, I = 0, q = 0 -dt/(RC) = dQ/Q Integrate Both Sides (tau) = RC [Time Constant] Lamp + - Charge not usually too useful Current?

  14. Charge Circuit? Lamp Pretty Similar… + -

  15. Problems? Freedom? • Today • Finish Chapter 26: RC Circuits • Freedom? • Post-Freedom • Magnetism & Induction: 27-29 • Post-Post Freedom • Finish induction & Review, Exam II

More Related