Voltage, Current and, Transducers. A pictorial tutorial.

Discussion in 'Audio Science' started by Pancakes, Aug 30, 2021.

  1. Pancakes

    Pancakes Friend

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    This is meant to be an easy to understand explanation not a course in electrical, mechanical or, acoustics engineering. Basically, it's meant to help non-technical people understand these concepts if they happen to be interested. Where I use numbers for math, they will be made up in order to make the math easy. They will however be appropriate and correct for the basic concept being explained.

    I will also use generalizations in order to explain an underlying concept. There are always exceptions to everything. I don't plan on addressing them (unless there is interest and it's something I have competence in).


    What is Voltage?

    Here we have a wire and some electrons (the red dots) in it.

    Wire.jpg

    Voltage (denoted by a capital "V") can be thought of as a measure of how far an electron can be pushed (moved) back and forth with a signal. They go back and forth since that's the nature of alternating current which is what a musical signal is. For the positive phase of a sinewave, an electron will move in one direction and for the negative phase it will move in the opposite direction. That's it. There's no more to it. Here's what it looks like when a low voltage is applied and when a high voltage is applied:

    Voltage.jpg

    What is Current?

    Current (denoted by a capital "I") is how many electrons can be moved past a certain point/plane of the wire. Low current will move a few electrons, high current will move many electrons.

    Current.jpg

    That's all there is to it.
     
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  2. Pancakes

    Pancakes Friend

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    Magnetic Forces

    This is how you move a diaphragm and make sound. Long story short, air needs to be displaced (moved) in order for sound to be created (sound being waves of air pressure). There are many ways to move things about but for reasons beyond the scope of this tutorial, we will accept that the electromagnetic force is the preferred method for a speaker.

    When an electron moves, it creates a magnetic force around itself (the physics explaining this are beyond scope - feel free to do some homework on your own). This magnetic force has a direction (all magnetic forces have a direction).

    The magnetic force changes direction based on the the direction of the current. This is what it looks like for a single electron:

    mag1.jpg

    Let's zoom out and take a look at what a group of electrons do:

    mag2.jpg

    Now we'll zoom out even further and see the conceptual net effect on a piece wire:

    mag3.jpg

    So far so good. Now we'll see what effects Voltage and Current have on the magnetic field. As we know, voltage is responsible for the distance that an electron travels. This results in the "distance" the magnetic field travels (in a circular trajectory). Low voltage = low distance of electron travel = low distance of magnetic field travel. The opposite is true for high voltage.

    mag4.jpg

    Cool. What does current do? Current (the number of electrons moving) defines the strength of the magnetic field. High current = many electrons = stronger magnetic field. The opposite happens with low current.

    mag5.jpg

    Next time, dynamic vs planar drivers.
     
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  3. Pancakes

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  4. Pancakes

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  5. Thad E Ginathom

    Thad E Ginathom Friend

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    Appreciated. Even after the first post I feel that I now understand more.
     
  6. Pancakes

    Pancakes Friend

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    Part 2 added.
     
  7. m17xr2b

    m17xr2b Friend

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    Great stuff.

    Once I grasped some basics this image expanded my view to a degree:
    [​IMG]

    Realising it's all just ripples in the electromagnetic field completed the picture for transformers and transducers for basic needs.

    For me voltage is just potential, by itself meaningless unless there's a resistance involved, voltage across a resistance equals current. Zero resistance doesn't exist anywhere in practical physics because of math otherwise we could have fixed our global energy issue. With simple tube amps it's all about controlling and balancing voltages and currents, Ohm's law is simple yet powerful in its application from calculating tube bias to figuring out copper losses in transformers and cables.
     
  8. Pancakes

    Pancakes Friend

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    That image is awesome lol :bow:

    I've decided to keep resistance out of my posts. I think it will muddy up the picture and actually I don't think it adds anything to the overall concept. Unless we're designing an electrical circuit, all we need to know is that the more voltage and current we have, the stronger and "longer" the magnetic field created is.
     
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  9. Pancakes

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    On second thought, I'll have to include resistance at some point. While it appears that I have these posts clearly planned, that's not the case lol. I have a general idea of the point I want to get across but don't really flesh out the details until I sit down to write a post.
     
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  10. Cspirou

    Cspirou They call me Sparky

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    I wouldn't exactly say that current is simply more electrons. A small number of electrons moving fast and a large number of electrons going slow can have the same current.

    I tend to like fluid analogies

    Pressure -> Voltage
    Flow rate -> Current
    Friction -> Resistance

    magnetism doesn't really have an analogue though
     
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  11. Pancakes

    Pancakes Friend

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    True. For completeness here is the wikipedia definition (emphasis is mine):

    "It is measured as the net rate of flow of electric charge through a surface or into a control volume."

    However, I'm doing my best to simplify things as much as possible so as to make the concepts accessible to more people. I'm cutting a few corners intentionally.
     
  12. Josh Schor

    Josh Schor Friend

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    this is great, really helpful in understanding
     
  13. Pancakes

    Pancakes Friend

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    Thanks. I've neglected adding more because life. But I haven't forgotten about it.
     

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