Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Important Concepts 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. Coulomb’s Law Electric Fields Electric Field Lines Electric Fields in Conductors Electric Flux Gauss’s Law Electric Potential Energy Electrostatic Potential Equipotential Lines Capacitance Resistance and Ohm’s Law (series & parallel) Kirchhoff’s Laws RC Circuits Magnetic Force on Particle – RHR Magnetic Force on Conductor Sources of Magnetic Fields Law of Biot-Savart Magnetic Flux – Ampere’s Law Magnetic Flux – Induction (Faraday & Lenz) Inductance RL Circuits RC Circuits AC Circuits 13. RC Circuits Example 2 – Discharging a Capacitor- + q = Q0 e − t / RC Mr. Kirchhoff says: q iR + = 0 C I = I 0 e −t / RC Exponential Decay – Which Curve is right? Strategy for understanding which curve is correct: Try to figure out what the current (or charge) would be just when the switch is closed (or opened) t=0 Then try to figure out what the current (or charge) would be after a very long time t=∞ I8 =0 the capacitor is fully charged and there is no current: I0=ε/R At t=0 there is NO charge on the capacitor – and therefore no voltage across capacitor I0 At t=8 I0 F = q vB⊥ r r r F = qv × B 15. Magnetic Force on a Charged Particle Units of Magnetic Field: 1 Tesla = 1 T = 1 Newton/(Ampere·meter) r r v C r = A B sin θ , r B . The direction of C The “Vector” or “Cross Product” v r r If C = A × B then the magnitude r of where θ is the angle between A and is given by the “Right Hand Rule”: Advice on using the Right Hand Rule: 1) First determine the plane that contains A and B. The cross product will point perpendicular to that plane. There are only two choices. 2) Use the Right Hand r Ruler to rpick which choice is correct. 3) If you are using F = qv × B , Remember that a negative charge will reverse the direction of the cross product! 15. Magnetic Force on a Conductor 16. Sources of Magnetic Fields Force between two infinite conductors 17. Magnetic Flux – Amperes Law The sign of the line integral gives the direction of the current Step 1: Curl the fingers of your RH in the direction of Integration Step 1: If Integral > 0, then current flows in the direction of thumb I Step 1: If Integral < 0, then current flows in the direction opposite that of the thumb I Electromagnetic Induction 18.Concept Magnetic Flux – InductionFlux Key is Magnetic Faraday’s Law r r dΦ B where Φ = B ⋅ dA = ∫ BdA cos φ B ∫ ε =− surface surface dt It doesn’t matter why the flux changes 1) Constant B, Changing Area: 2) Constant Area, Changing B: 3) Constant Area, Constant B, Changing Cos φ: Induced Electric Fields Faraday’s Law hold even if there is no Motion and no Magnetic Field Φ B = BA = µ0 nIA dΦ B dI = − µ0 nA dt dt Faraday’s Law implies that there is an “Induced” Electric Field ε =− r r ∫ E ⋅ dl = ε r r dΦ B ∫ E ⋅ dl = − dt This “Induced” Electric Field is a non-electrostatic field that arises, not from static charges, but from a changing B field alone. Direction of the Induced EMF’s and Currents In the previous problem, we found the direction of the induced current by noting that the force resulting from the induced current had to oppose the applied force. This obbservation can be generalized into: Lenz’s Law The direction of any magnetic induction effect is such as to oppose the cause of the effect 19. Inductance Mutual Inductance SELF-INDUCTANCE 20. RL Circuits Discharging: 21. The L-C Circuit x = A cos(ωt) ω stays constant A changes A stays constant ω changes Representation of Sinusoidal Motion Using Rotation of a “Phasor” Current and Voltage in AC Circuits Frequency Dependence of Resistance and Reactance