Chapter 27 Magnetism

Introduction Our approach –Review of E&M interaction ideas –Magnetic fields & magnets (initial ideas) –Magnetic field and currents (initial ideas) –Force on a current in a B-field –Force on a charge in a B-field –Torque on a current loop in a B-field –The Hall Effect

Electrical & Magnetic interactions How have people understood the relation between electrical and magnetic interactions? Ancient views 19 th Century: Classical E&M 20 th Century: Special Relativity 20 th Century: Quantum Field Theory

Magnets & Magnetic Field Magnetic poles Origin of pole names The Earth’s magnetic field –Quick survey – _nmp_e.phphttp://gsc.nrcan.gc.ca/geomag/nmp/daily_mvt _nmp_e.php

Currents & Magnetic Fields Shape and direction of field caused by a current (initial idea) –Whiteboard example Use of the right hand rule to determine the direction of the magnetic field –Question posing

Force on a current in a B-field The force on a current element and current –Vector expression and picture The magnetic field as not a force field, as was the electric field –Why?

Force on a charge in B-field The force –Vector expression and picture Relation to motion Example: velocity selector Example: electron behavior Force from E and B fields –What is it? And corresponding picture? Effect on motion –What is it?

Torque on a current loop in B-field The torque –Why expected? Magnetic dipole moment –Vector expression and picture The potential energy –Vector expression and picture Review of key formulas

The Hall Effect Physical situation –Describe the situation Underlying dynamics –Provide an explanation

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