Lecture 19 - Magnetic field, field lines, moving chages

Lecture 19 - Magnetic field, field lines, moving chages -...

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1 Lecture 19 Magnetic fields field lines Magnetic fields, field lines, moving charges. Quick reminder: E field Electric force between two charges 12 2 0 1 ˆ 4 qq Fr r  Huge question: How is this force communicated over a distance? How does charge 2 know about charge 1? Partial answer: Charge 1 sets up an electric field If a second charge is placed in electric field then it experiences a force FqE Remarkable conceptual leap… Electric field extends over ALL space If charge 1 moves, field changes Similarly a magnet sets up a magnetic field B In a few weeks time we will show that it is the moving charges (electrons in atomic orbitals) that create the B -field For now we will assume we can somehow create a -field and look at the force it exerts on charged particles Magnetic field B-field • extends to all points in space • at every point, there is a vector B that has a particular magnitude and direction • magnetic field lines: like E-field lines: • B-field is tangent to them at all points • magnitude of B-field is indicated by the density of lines Magnetic dipole field B-field leaves N-pole and go to S-pole B-field is continuous, no monopoles (“magnetic charge”) There is nothing special about a “pole”: it’s just where the material ends.
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This note was uploaded on 09/21/2011 for the course PHYS 222 taught by Professor Johnson during the Spring '07 term at Iowa State.

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Lecture 19 - Magnetic field, field lines, moving chages -...

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