29 303l magnetic force and field ch29 magnetic force

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Unformatted text preview: Magnetic Force and Field (Ch.29) 303L: Magnetic Force and Field (Ch.29) Magnetic Force The Biot-Savart Law on a current-carrying conductor Force exerted by an electric current on a nearby magnet Experiments by Biot and Savart m agnetic field dB at a point P associated with a length element ds of a wire carrying a current I • A hanging wire deflects to the left (right) if current in the wire flows upward (downward) • The vector dB is perpendicular both to ds and to ˆ r • The magnitude of dB is inversely proportional to r2 • The magnitude of dB is proportional to the current and to the magnitude of ds • The magnitude of dB is proportional to sinθ, where r rr FB = q vd × B nAL ( ) θ is the angle between ds and r r r µ Ids × r ˆ dB = 0 4π r 2 r rr FB = I L × B • Force on a straight segment of current-carrying wire in a uniform magnetic field 303L: Magnetic Force and Field (Ch.29) µ0 = 4π ×10-7 Tm/A r µI B= 0 4π r ˆ ds × r r2 permeability of free space 303L: Magnetic Force and Field (Ch.29) The Biot-Savart Law The Biot-Savart Law Magnetic field surrounding a thin wire • Magnetic field lines ∫ Magnetic field surrounding a current loop circles concentric with the wire in plane perpendicular to the wire • Magnitude of B constant on any circle of radius a B= µ0 I 2πa • Direction of B grasp the wire with the right hand, positioning the thumb along the direction of the current – the fingers wrap in...
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This document was uploaded on 01/15/2014.

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