# Lec17-2 - ture 17-1 ture Amperes Law in Magnetostatics...

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cture 17- cture 17- 1 Ampere’s Law in Magnetostatics The path integral of the dot product of magnetic field and unit vector along a closed loop, Amperian loop , is proportional to the net current encircled by the loop, 0 t C C C B dl B dl I μ = = ur r g Ñ Ñ Choosing a direction of integration. A current is positive if it flows along the RHR normal direction of the Amperian loop, as defined by the direction of integration. Biot-Savart’s Law can be used to derive another relation: Ampere’s Law 0 1 2 ( ) i i -

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cture 17- cture 17- 2 Magnetization and “Bound” Current in Matter Strong externally applied field B app aligns the magnetic moments in matter. (M) Magnetization M V μ = ur uur d M dV = ÷ ur uur m app m B B χ = ur ur 0 m app app M B M B μ = uur ur uur ur 0 (1 ) a a p m pp p B M B B = = + + ur uur ur ur ( 29 0 0 app app m m B B K B K = = ÷ ur ur ur
cture 17- cture 17- 3 Hysteresis for a Ferromagnet Lack of retraceability shown is called hysteresis. Memory in magnetic disk and tape Alignment of magnetic domains retained in rock (cf. lodestones) Area enclosed in hysteresis loop μ Energy loss per unit volume hard magnet: broad hysteresis loop (hard to demagnetize, large energy loss, high memory) soft magnet: narrow hysteresis loop (easy to demagnetize,…)

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cture 17- cture 17- 4 BRIDGE OF NAILS 6B-13
cture 17- 5 Reading Quiz 1 A uniform magnetic field makes angle of 60 degrees with respect to the axis of a flat circular coil with 150 turns and a radius of 4 cm. The magnitude of the magnetic field increases at the rate of 55.0 T/s while its direction remains fixed. What is the induced emf in the coil? A) 5.9 V

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## This note was uploaded on 12/07/2011 for the course PHYS 241 taught by Professor Wei during the Fall '08 term at Purdue University.

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Lec17-2 - ture 17-1 ture Amperes Law in Magnetostatics...

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