Lecture 19 preview mar18

# Lecture 19 preview mar18 - Lecture 19 Maxwell's Equations...

This preview shows pages 1–6. Sign up to view the full content.

Lecture 19 Maxwell’s Equations Faraday says, “changing magnetic flux can generate electric currents” •Changing B: magnet and wire loop •Changing area: AC generator

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

View Full Document
Induced E fields and Maxwell’s 3 rd - = Φ - = * * ) ' ( 3 ' surf path rd A d B dt d dt d l d E Law s Faraday s Maxwell X B increasing X X X Changing B fields induce E fields (that produce ξ) 2 nd Important point: take away the wire and the E fields are still there! Question 1: How does E depend on r? (r>R) A. ~r B. ~r 2 C. ~1/r D. ~1/r 2 r R dt d r E so dt d r E Φ = Φ = π 2 1 2 How about E for r<R??? Electric fields can be generated by changing magnetic flux
(A week ago) Applications of Ampere’s Law 1. ∞ straight wire: (obvious) (cylindrical symmetry) B2πr = μ 0 I 1. B inside ∞ straight wire of radius R: (cylindrical symmetry) Ex 28.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I out (for r<R) ) ( 2 2 0 2 2 0 0 R r R I B R r I i r B l d B inside π μ = = = =

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

View Full Document
Eddy Currents (getting E-motional about a backwater effect…. .) Let’s consider the motional EMF of a conducting sheet moving/spinning through a B field. Mobile charges are spun through B with v to the left. This generates downward current in the yellow-shaded region. F mag on these eddy currents is to the right---a drag/braking force on the spinning wheel: Let’s see if we can detect this braking force……… DEMOS
Maxwell’s Round-up I l d B A d B dt d l d E q A d E B exclosed = = Φ - = = 0 0 0 μ ??

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 04/04/2008 for the course PHYSICS 240 taught by Professor Davewinn during the Spring '08 term at University of Michigan.

### Page1 / 11

Lecture 19 preview mar18 - Lecture 19 Maxwell's Equations...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online