Marko Rodin Coil -- 007 Device

[minnie]

   Webby,
         I found Wiki was helpful with regards to square wave.
              John.

[MileHigh]

The answer to your question is because it's often much easier to determine how a circuit that consists of capacitors, inductors, and resistors will respond to a sine wave compared to a square wave.  So instead of dealing with a difficult problem based on a square wave, you break it down into several easy to answer problems based on a series of sine waves.  Then when you start to think like this, you are always thinking about the frequency content in a given waveform.

The circle is a form of perfection, it is a pure form.  A sine wave is just one component of a circle.  If a circle is two-dimensional, then a sine wave is like a one-dimensional version of a circle.  A sine wave is a perfect form, a pure single tone.  A pure sine wave has a width of zero in the frequency spectrum.

Put a sine wave and a cosine wave together at a right angle and you get a perfect circle.  You can analyze just about anything by looking at how it responds to perfect sine waves.

[minnie]

Webby,
          I just don't think you're getting it.
An "ideal" square wave isn't achievable in practice.
        John.

[minnie]

   Webby,
        I give up!!!
            John.

[MileHigh]

John,,

I play in the mechanical world and a constant force on and off is a square wave,, perfect and simple and true.

Besides John,, there are no such things as "ideal",, I thought you understood that.

No, using the same set of criteria, there is no such thing as a perfect square wave in the mechanical world either.