magnetic_sources

magnetic_sources - for combination of wire segments(3...

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Magnetic Sources – ch. 28 B fields due to electric current or moving electric charge. " Magnetic charge " postulated but never seen (yet. ..) (1) Field due to moving charge: d r B = μ o 4 π q r v × r r r 3 , due to charge q , const. velocity r v . μ o = 4 π× 10 7 T m/A is permeability of free space . (2) Biot-Savart law: d r B = o I 4 π d r l × r r r 3 , due to current I in small wire d r l . or, r B = o I 4 π d r l × r r r 3 , total is sum over wire length . use superposition
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Unformatted text preview: for combination of wire segments (3) Ampere's law: r B ∫ ⋅ d r l =μ o I encl , around any closed loop . ( d r l positive in the right-hand rule direction.) (4) Gauss's law for magnetism, chapter 27: r B ∫ ⋅ d r A = also helps determine fields. Some results: • Infinite wire, B = μ o I 2 π r • Solenoid (infinite) B =μ o NI / l =μ o nI • Long parallel wire forces, F / l =μ o I 1 I 2 /2 π d...
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