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Unformatted text preview: Physics 2102 Magnetic fields Physics 2102 Gabriela González L Magnetic force on a wire d v L i t i q = = L B v q F d × = B L i B q L i q F × = × = B L i F × = B L d i F d × = Note: If wire is not straight, compute force on differential elements and integrate: Example iLB F F = = 3 1 θ iBRd iBdL dF = = By symmetry, F2 will only have a vertical component, iBR d iBR dF F 2 ) sin( ) sin( 2 ∫ ∫ = = = π π θ θ θ ) ( 2 2 3 2 1 total R L iB iLB iRB iLB F F F F + = + + = + + = Notice that the force is the same as that for a straight wire, L L R R and this would be true no matter what the shape of the central segment!. Wire with current i. Magnetic field out of page. What is net force on wire? Torque on a current loop: Principle behind electric motors. Net force on current loop = 0 iaB F F = = 3 1 ) sin( 1 θ F F = ⊥ ) sin( θ τ iabB b F Torque = = = ⊥ For a coil with N turns, τ = N I A B sin θ , where A is the area of coil Rectangular coil: a x b, current = i But: Net torque is NOT zero! n...
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This note was uploaded on 11/18/2011 for the course PHYSICS 2102 taught by Professor Dowling during the Fall '10 term at LSU.
 Fall '10
 DOWLING
 Physics, Force

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