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direction of B 303L: Magnetic Force and Field (Ch.29) 303L: Magnetic Force and Field (Ch.29) 2 Magnetic Force Ampere’s Law between two parallel conductors describes creation of magnetic fields by current • The current I2 produces magnetic field B2 = µ0 I 2
2πd • The product rr
B ⋅ ds on the circular path defined by compass needles: • The wire carrying I1 in magnetic field is subject to force r µ0 I r ∫ B ⋅ ds = B ∫ ds = 2πr (2πr ) = µ I rr
r
µII
F1 = I1 l × B2 = 0 1 2 l
2πd 0 • Parallel conductors carrying currents in the same direction
attract each other, and parallel conductors carrying The line integral of currents in opposite directions repel each other rr
B ⋅ ds around any closed path equals µ 0 I , where I is the total steady current passing through any surface bounded by the closed path r •When the magnitude of the force per unit length between two long parallel wires that carry r ∫ B ⋅ ds = µ I identical currents and separated by 1 m is 2×10-7 N/m, the current in each wire is 1 A 0 •When a conductor carries a steady current of 1 A, the quantity of charge that flows thr...

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