300x Filetype PPT File size 0.26 MB Source: phys420.phas.ubc.ca
Motors and Generators
• Simple devices that use basic principles of electromagnetic
theory
• Technologically important
• Motors drive everything from hybrid cars to vibrating
phones.
• Most electrical power is provided by generators
• Work on the same principles: converting between
mechanical and electrical energy using the magnetic force
Electric and Magnetic Fields
• Electric and magnetic fields are vector fields
• A vector has magnitude and direction
• A vector field describes a vector for every point in space
Electric Force
• An electric field exerts force on electric charge.
• The force is in the direction of the field - charges get pushed in
the direction of the field.
• F = qE (q is magnitude of charge).
Magnetic Force
• Magnetic fields exert force on moving charges
• Force is perpendicular to field and to velocity
• Units of Gauss: 1 G = 1 N*s/C*m
• F = qvBsin(ϴ) : ϴ is the angle between v and B.
B
Electric Motors
• In a motor, current passes through a coil of wire in a
magnetic field
• Magnetic field exerts force on charges moving in the coil
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