We call these generators. Ok, that's a little sarcastic, but the principle of spinning windings past magnets has the effect you are talking about.linux kid said:If magnetic fields aroung a coil of wire were turned on and off at a certain frequency, would it generate some form of energy?
Er.. you do?WhyIsItSo said:I suppose if you turned the magnetic fields on and off, you'd generate a square wave, while a generator creates a sine wave,
Which part are you talking about?ZapperZ said:Er.. you do?
The current generated in the coils would be proportional to the rate of flux across the coils' area, i.e. [itex]\frac{d\Phi}{dt}[/itex]. So if you have a sine wave, the time derivative of that would also be a sinusoidal wave with a phase shift (ignoring self induction).
Oh, sorry. I misread your statement. I thought you said that if the generator of the external field has a square wave, the induced current can still be sinusoidal.WhyIsItSo said:Which part are you talking about?
In the hypothetical scenario where a magnetic field was either on or off, and oscillated between these states at a high enough frequency, would that not generate a square wave?
If referring to my comment about a generator, do they not create a sine wave? Is not a sine wave sinusoidal?
This is true. The emf induced in the coil, and thus the current in the coil, is proportional to the rate of change of the magnetic flux through the coil. Well, if you are able to "immediately" switch the B-field between on and off states, the rate of change is infinity and this occurs in a no time, which would mean an infinite current for a time period of zero. This is modeled by a train of dirac delta functions. Practically, however, there would be a very large rate of change in the flux over a very small finite time period, which would produce very large spikes of current that occur over very small time periods, similar to the ideality of the delta function, but with finite height and width.phun said:I think you'd get a train of delta functions (pulses) of electricity that way.