lect20-nov14

# lect20-nov14 - Physics 227: Exam 2 Information! Exam 2: 16...

This preview shows pages 1–8. Sign up to view the full content.

Physics 227: Exam 2 Information Exam 2: 16 questions covering chapters 25 – 28 Thursday, Nov 17, 2011, 9:40 PM - 11:00 PM Room assignments: A-I ARC 103 J-M SEC 111 (may start late) N-R PLH S-Z Beck Auditorium, Livingston Campus!!! ( NOT Hill 114 ) Anyone with a conFict should contact Prof. Cizewski [email protected] TODAY!! Bring pencils, one formula sheet w/ anything you want NO calculators, NO cell phones, NO electronics needed or allowed!

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Outline Lecture 20 Review of Lecture 19 & Faraday’s law Self inductance and inductors How a time-varying current in one coil can induce an emf How to relate the induced emf in a circuit to the rate of change of current in the same circuit The R-L circuit: how to analyze circuits that include both a resistor and an inductor (coil) Magnetic field energy – how to calculate the energy stored in a magnetic field
Maxwell’s equations Gauss’s Law for E Gauss’s Law for B Ampere’s Law (conduction + displacement currents) Faraday’s Law Lecture 19 Review E d A = q enclosed ε 0 B d A = 0 (no magnetic charges) E d = d Φ B dt B d = μ 0 ( i conduction + 0 d Φ E dt ) enclosed where 1 0 μ 0 = c

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Faraday’s Law: If change in magnetic ±ux, then EMF is induced Physics 227: Lecture 20 EMF = d Φ B dt where Φ B = B d A = BA cos θ (if B is uniform over A) Note minus sign (Lenz’s Law): self-induced EMF opposes change in current Faraday’s Law PhET
Previous assumption not quite correct: When switch closed I ε /R immediately Faraday’s law prevents from happening Rather, as current increases vs time, Φ Β due to this current also increases This increasing ±ux induces EMF that opposes change in Φ Β => opposing EMF means gradual increase in the current This effect = SELF-INDUCTION Isolated circuit and induced EMF EMF = d Φ B dt = d dt BA Isolated circuit: switch, resistor, source of EMF Induced EMF

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
When switch closed I ε /R immediately Faraday’s law prevents from happening Rather, as current increases vs time, Φ Β due to this current also increases This effect = SELF-INDUCTION = L Isolated circuit and induced EMF EMF induced = N d Φ B dt = L di dt L = N Φ B i Isolated circuit: switch, resistor, source of EMF Assume same ±ux through all N turns Inductance depends upon geometry
Purpose of inductor: oppose any variations in the current through the circuit; Unit of inductance = Henry = Volt-second/Ampere Examples: Inductor in a DC circuit helps to maintain a steady current despite Fuctuations in the applied EM± Inductor in an AC circuit tends to suppress variations of the current that are more rapid than desired Inductors are circuit elements

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 01/03/2012 for the course PHYSICS 750:227 taught by Professor Ronaldgilman during the Fall '11 term at Rutgers.

### Page1 / 31

lect20-nov14 - Physics 227: Exam 2 Information! Exam 2: 16...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online