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Physics 2102 Jonathan Dowling. Lecture 21: FRI 06 MAR. Magnetic fields Ch.28.8-10. 28.8 Force on Current in Wire 28.9 Torque on Current Loop 28.10 Magnetic Dipole Moment. L. Magnetic Force on a Wire. i. (28-12). Torque on a Current Loop:. Principle behind electric motors.
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Physics 2102 Jonathan Dowling Lecture 21: FRI 06 MAR Magnetic fields Ch.28.8-10 28.8 Force on Current in Wire 28.9 Torque on Current Loop 28.10 Magnetic Dipole Moment
L Magnetic Force on a Wire.
i . (28-12)
Torque on a Current Loop: Principle behind electric motors. Rectangular coil: A=ab, current = i Net force on current loop = 0 But: Net torque is NOT zero! • For a coil with N turns, • = N I A B sinq, where A is the area of coil
Right hand rule: curl fingers in direction of current; thumb points along m Define: magnetic dipole moment m Magnetic Dipole Moment We just showed: t = NiABsinq N = number of turns in coil A=area of coil. As in the case of electric dipoles, magnetic dipoles tend to align with the magnetic field.
+Q p=Qa -Q QE q QE Electric vs. Magnetic Dipoles