# L29_a - AMPERE'S LAW (22.9 in text) Ampere's law: relates...

This preview shows pages 1–4. Sign up to view the full content.

AMPERE’S LAW (22.9 in text) Ampere’s law: relates magnetic field around a closed path to current through a surface bounded by that path Useful for calculating B r only in case of high symmetry o Similar tool for magnetic fields that Gauss’s law is for electric fields Plan: 1 st : state Ampere’s Law 2 nd : explain what it means 3 rd : justify by showing that it gives previous result for field around a long wire

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

View Full Document
WHAT IS AMPERE’S LAW? loop through 0 loop closed around I s d B µ = r r WHAT DOES THIS MEAN? Look at a closed path (any shape) around a current I At each point around path, can take scalar product of B r with small segment of path s d r ± result: s d B r r loop closed s d B r r means sum s d B r r for all segments around the loop ± Ampere’s law says that resulting sum equals I 0 where I is the TOTAL current “threading” through the closed loop. I ut of screen/page B B B ds ds ds
AMPERE’S LAW: loop through 0 loop closed around I s d B µ = r r True for ANY loop (called Amperian loop) around a steady current BUT: ± Only helpful for calculating field for special (symmetric) cases o i.e. ones for which B can be factored out of the integral ± Cases where Ampere’s law might be useful: o B r is known constant over part of the path (by symmetry) o B r parallel to

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 03/08/2012 for the course PHYSICS 1051 taught by Professor Michaelmorrow during the Winter '12 term at Memorial University.

### Page1 / 11

L29_a - AMPERE'S LAW (22.9 in text) Ampere's law: relates...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online