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General audio topics that don't fit into specific categories.

Just like an antenna.

The electrical wave comprises electric and magnetic fields. An unterminated conductor supports a series of standing waves, where the boundary condition is that the current be zero at the unconnected end. The electric field components of the standing waves will be maximum at the unterminated end, and the magnetic field components will be null (because the current is zero).

The fundamental frequency is the mode where the unterminated wire is half the wavelength of the electrical wave. The harmonics are related by integer multiples of the fundamental. Thus, the first harmonic (the second mode) has the full sine wave contained on the unterminated conductor, the second harmonic (the third mode) has 3/2 of the sine wave contained on the unterminated conductor, etc.

This oversimplifies what happens in a power cord, because there are also modes to do with waves between pairs of the conductors, and the velocity of propagation may not be constant for all important modes.


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  • Just like an antenna. - Al Sekela 16:08:42 08/29/08 (0)

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