lecture 13

lecture 13 - 21.7 Magnetic Fields Produced by Currents...

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21.7 Magnetic Fields Produced by Currents Moving charges experience a force in magnetic fields. F = qvB sin θ Currents also feel a force in a magnetic field. Until 1820 everyone thought electricity and magnetism were completely F = ILB sin θ separate entities. Then Hans Christian Oersted discovered the following: lectric currents create magnetic fields! D Electric currents create magnetic fields! A more general statement is that moving charges create magnetic fields. Stationary charges create Electric Fields This discovery helped create the field of Electromagnetism. hat do the magnetic field lines look like around a long straight current arrying wire? Moving charges (constant v ) create Magnetic Fields. What do the magnetic field lines look like around a long, straight, current-carrying wire? The current produces concentric circular loops of magnetic field around the wire. B Remember, the magnetic field vector at any point is always tangent to the field line! The current I is coming out at you. I

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We determine the direction of the magnetic field around a long current carrying wire by using RHR-2. RHR-2 : Point the thumb of your right hand in the direction of the current, and your fingers curl around the wire showing the direction of the field lines. B I x x x x x x x x x x x x B I B Experimentally, it is found that I B . 1 r B and The magnetic field created by a long straight wire is: r I B o π μ 2 = o is the permeability of free space: A m T 10 4 7 × = o
So electrical currents create magnetic fields of their own. These fields can effect the motion of other moving charges or currents.

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lecture 13 - 21.7 Magnetic Fields Produced by Currents...

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