Marko Rodin Coil -- 007 Device

[picowatt]

That makes no sense to me.
If the wave form is pure,how can it have harmonic content?.
If there is any ripple !such as shown in PWs animation! in the wave form,then how is it a pure wave form?.

The animation started out as a pure waveform, that is, a single sine wave.  As additional harmonics were added to that pure sine, it was no longer a "pure waveform" but instead morphed into a square wave as harmonics were added.  Note that the repetition rate remained at the same frequency as the original sine wave, but as it became a square wave, its frequency content increased as harmonics (additional sine waves) were added to the original, single frequency, pure sine wave.

To me,a pure square wave form would have no harmonic ripple as shown in PWs animation. For example,a pure square wave would be like placing a scope across a 12 volt battery for 1 second,and then disconnect it for one second--and repeat process. This to me would show a pure 12 volt square wave with a 50% duty cycle. This harmonic ripple in a square wave can only come from the equipment ,and not the source.

The square wave you are creating has a frequency of .5Hz.  That would be the fundamental, the first sine wave necessary to make that waveshape.  Your waveform has very fast edges, so you know it can't be just a pure .5Hz sine wave.  So, we start adding harmonics to the .5Hz sine wave until we arrive at the square wave you created.  Conversely, we can look at your square wave and mathematically analyze it, that is, disassemble it, to determine what frequencies are contained in that waveshape.   

The ideal voltage source in MH's question is producing a long period rectangular waveshape that does not have a 50% duty cycle and has very fast (assumed to be instantaneous) transitions.  The fundamental will have a very low (sub 1Hz) frequency but in order to make the waveform rectangular, and with very fast transitions, many harmonics must be added to the fundamental to create that waveshape.

Only a pure (non-distorted) sine wave contains just one particular frequency.  As soon as that sine wave deviates in the slightest from being a pure sine wave (starts to look "ugly") it contains additional frequencies (harmonics).  This is what is meant by harmonic distortion in an amplifier.  A pure sine wave goes in, but that sine wave, if distorted in the least, will contain additional harmonics on the amplifier output.  if driven to the point of clipping, the output begins to resemble a square wave and contains a lot of harmonic content.

That GIF animation from the Wiki link shows how sine waves are added together to make a square wave.

Again, EVERY waveshape imaginable can be disassembled into a group of various sine waves at various amplitudes  that make up that waveshape.

If you have an audio graphic equalizer, try feeding a 1 or 2 kHz square wave into it while excercising the controls and watching the output on a scope.  Then feed in a 1 or 2kHz sine wave and repeat your observations.  This will readily demonstrate that the square wave does indeed contain additional frequencies.

PW 

[MileHigh]

And the truth is that over the past five years this extremely important subject matter about understanding the concepts relating to the frequency content in signals has probably been covered between a dozen and two dozen times, sometimes in depth.  Some people obviously were not listening and the revolving door of knowledge keeps on turning.

Rolling on the river...

[poynt99]

That makes no sense to me.
If the wave form is pure,how can it have harmonic content?.

Perhaps the term "pure" is confusing to some, although the techies all know what we mean. Pure, as in exact, precise. When I refer to a "pure" square wave, that means perfectly flat tops and bottoms, and infinitely-fast transitions. And as such, this wave form is going to contain a hell of a lot of frequency harmonics (odd only) going to infinity (although the amplitude of each successive odd harmonic decreases).

If there is any ripple !such as shown in PWs animation! in the wave form,then how is it a pure wave form?.

It isn't. The purpose of the demo was to show you that the square wave is made up of many frequency components, and that the more harmonics you add, the more perfectly "square" it becomes. Who referred to PW's animation as demonstrating a pure square wave?

To me,a pure square wave form would have no harmonic ripple as shown in PWs animation. For example,a pure square wave would be like placing a scope across a 12 volt battery for 1 second,and then disconnect it for one second--and repeat process. This to me would show a pure 12 volt square wave with a 50% duty cycle.

Yes, but do you understand that any "pure" (perfect)  square wave contains many odd-ordered frequency components called harmonics?

[MileHigh]

Well that is incorrect.
The correct answer would be--nothing happens at all.

Brad

No my answer was not a correct answer, it was just a joke.

The correct and serious answer would be as follows:

There is no point in even considering what would happen if you had an ideal current source connected to an open circuit with no means of conduction between the two terminals.  It is what is essentially an invalid thought experiment, just like saying connecting an ideal voltage source to a short circuit is an invalid thought experiment.

The real takeaway is as follows:

For an ideal voltage source, as the load resistance tends towards zero, the current tends towards infinity and the power output tends towards infinity.

For an ideal current source, as the load resistance tends towards infinity, the voltage tends towards infinity and the power output tends towards infinity.

Zero output power for a voltage source is an open circuit for the load.
Zero output power for a current source is a short circuit for the load.

A capacitor acts like a temporary ideal voltage source.
An inductor acts like a temporary ideal current source.

These concepts should become like a second nature for an electronics hobbyist.

MileHigh

[picowatt]

,, so then you are stating that a square wave can be described by an appropriate number of rectangles??

No, we are saying that a square wave can be described by an appropriate number of sine waves (a fundamental frequency and odd harmonics) that when summed together results in a square wave.

PW