S13Phys2BaLec28C

# If we were to make n loops of this wire then our

• Notes
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where A is the area of the loop. If we were to make N loops of this wire then our equation would become: τ tot = NIAB sin θ

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. . Current Loop B B I F F I I
Magnetic Moment The first part of right side of the last equation (NIA) is dependent on properties of the loop. Because of this we define the magnetic dipole moment vector, μ , of the wire: The magnetic dipole moment vector points perpendicular to the plane of the loop(s), a normal so to speak. μ = NIA

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Magnetic Moment The angle θ will be between μ and B such that: τ = μ × B = μ B sin θ A magnetic dipole moment located in an external magnetic field will have a magnetic potential energy, U. U will depend on the dipole’s orientation in the field, such that: U will be least value when μ and B are parallel. U will be greatest when μ and B are anti- parallel.
Electric Motor An application of this concept is the electric motor. An electric motor converts electrical energy to mechanical energy (specifically rotational kinetic energy). A simple electric motor consists of a rigid current- carrying loop that rotates when placed in a magnetic field. To provide continuous rotation in one direction, the current loop must periodically reverse, (AC current).

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For Next Time (FNT) Start reading Chapter 29 Keep working on the homework for Chapter 28
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• Spring '08
• schuller
• Charge, Force, Magnetic Field, Electric charge, Ftop B

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