L25_a - MAGNETIC FORCE & MAGNETIC FIELD (Chapter 22)...

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Unformatted text preview: MAGNETIC FORCE & MAGNETIC FIELD (Chapter 22) Read historical background in 22.a1 • Magnetism known of for over 2000 years. • Magnets known to have two poles o North points to Earth’s North Pole (which is a south magnetic pole!) o South points to Earth’s South Pole (which is a north magnetic pole!) • Poles cannot be separated – no magnetic monopoles (so far) • Connection between magnetism and electricity dates to 1819 (Oersted) • Important contributions in early 1820’s from Ampére, Faraday, Henry • Relationship between magnetic field and changing electric fields and vice versa formulated by Maxwell in 1861 MAGNETIC FIELD B r ≡ • Magnetic field is a VECTOR (important) • Source can be permanent magnet OR nearby electric current Can use MAGNETIC FIELD LINES to represent how magnetic field depends on location in space N S • Magnetic Field Lines – RULES o Lines start and stop on poles of a magnet OR lines form closed loops around current-carrying wires ¡ No such thing as a magnetic monopole ¡ For magnet – lines start at North pole and end at South pole o MAGNITUDE of magnetic field | | B r indicated by DENSITY of lines o DIRECTION of magnetic field at a point is tangent to field lines at point ¡ Direction of magnetic field at some location is the direction that a compass needle would point at that location. N S MAGNETIC FORCE B F r on a moving charged particle (charge q , velocity v r ) Experimental observations show: 1 st : For magnitude, find q F B ∝ | | r and v F B ∝ | | r BUT = B F r if v r parallel to B r 2 nd : For direction, find that if...
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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.

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L25_a - MAGNETIC FORCE & MAGNETIC FIELD (Chapter 22)...

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