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Transcript
Faraday’s Law of Induction Magnetic flux = A B cos B A A changing magnetic flux generates an induced voltage (emf = electromotive force) = (ABcos )final – (ABcos )initial V = [emf] = - N / t Motional EMF Voltage induced in a moving conductor Velocity Vmax = [emf] = -Blv Length Induced emf depends on angle between the Magnetic field and the velocity direction. Lenz’s Law An induced emf gives rise to a current whose magnetic field opposes the original change in flux new, larger B Induced current Induced B Lenz’s Law Exercises Applications of Faraday’s Law Eddy Currents Transformer: • Primary and secondary coils • Iron yoke (to contain flux) • AC voltages only ! • No loss -> Input power = output power V2 N2 I1 V1 = N1 = I2 Electric Generator: angular velocity w = 2pf Alternating (AC) voltage = BAcos(wt) t V t Electromagnetic Waves 0 0 0 Speed of light (Constant of Nature) c = 299 792 458 m/s (3 x 108 m/s) Also: c = frequency times wavelength c=lf
