Lec21V

# Lec21V - Lecture 21-1 Lecture Next Tuesdays lecture is...

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

Lecture 21 Lecture 21 -1 Next Tuesday’s lecture is cancelled, to compensate for the second evening exam. Unlike exam 1, there will be no review session. All Physics 241 recitations are cancelled for Wednesday, April 6, 2011 – as was stated in the course syllabus. (Reminder/clarification .)

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

View Full Document
Lecture 21 Lecture 21 -2 Maxwell’s Equations (so far) Gauss’s law 0 inside S Q EdA ε = ur ± ± Gauss’ law for magnetism 0 S BdA = u ru r ± ± Faraday’s law B C d Ed l dt Φ =− u rr ± ± Ampere’s law * 0 C Bdl I μ = u ± ± Note: Klingon boxes on the integral symbols denote “closed surface or loop” [Mac vs PC] Flux and current are what penetrate a surface spanning the loop C
Lecture 21 Lecture 21 -3 Parallel-Plate Capacitor Revisited 0 S S Bd l I μ = u rr ± ± For surface S 1 , I s = I , but for surface S 2 , I s = 0 ?? Wait, LHS is the same (because C is the same)! You could make this work if a fictitious current I d is added to I s in such a way that I d is zero for S 1 but is equal to I for S 2 . 0 00 E dQ dV A dV IC dt dt d dt dE d A dt dt ε εε == = Φ 0 E d d I dt Φ will work. Q -Q E ur 0 E = B=0 ? Not experimentally! And is called the displacement current

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

View Full Document
Lecture 21 Lecture 21 -4 Displacement Current James Clerk Maxwell proposed that “A changing electric field induces a magnetic field” , in analogy to Faraday’s law: “A changing magnetic field induces an electric field”. Ampere’s law is revised to become Ampere-Maxwell law 00 0 0 () E d C d Bdl I I I dt μμ μ ε Φ =+ + ur r ± ± is the displacement current . 0 E d d I dt Φ where
Lecture 21 Lecture 21 -5 MAXWELL’S EQUATIONS “COMPLETED” The equations are often written in slightly different (and more convenient) forms when dielectric and/or magnetic materials are present. There are also differential forms of these equations.

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.

{[ snackBarMessage ]}

### Page1 / 24

Lec21V - Lecture 21-1 Lecture Next Tuesdays lecture is...

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

View Full Document
Ask a homework question - tutors are online