The Third Example


So far, these examples demonstrate the utility of a universal notation. The problem is, they are both from the world of mathematics; although math has concrete manifestations, it is intrinsically abstract. Are there any examples not from mathematics?

I then draw Figure 6.4 on the whiteboard.

Figure 6.4. First electric circuit.


What is stunning about this picture is that as soon as I complete the drawing and say the words, "Here I have a simple circuit with a battery and a resistor," heads begin to bob. Of course, this is probably the simplest electrical circuit you could draw, but no matter. Just as the audience will applaud for itself when it recognizes the opening notes of Beethoven's Fifth Symphony, it will feel good about recognizing something technical.

Without giving them too much time to think about it, I quickly add the symbols for a voltmeter and an ammeter, as shown in Figure 6.5.

Figure 6.5. Second electric circuit.


And, in a final bold stroke, I note that if the battery is 6 volts and the resistor 6 ohms, then 1 ampere of current flows in the circuit, as shown in Figure 6.6.[2]

[2] It is important for the effect to use the symbol for ohms, not the word "ohm."

Figure 6.6. Third electric circuit.


Now, people know what a 6 volt battery is; they can buy one in the store. And most people will have a recollection, however vague, that resistors are measured, or come, in units of ohms. So when you finally draw the "1 A" on the diagram, indicating that 1 ampere of current flows in the circuit (note that I even indicate the direction of flow!), people are totally convinced they know what you are talking about, even if they never could remember Ohm's Law.

This is a very good time to mention that a Swedish student and an Australian hobbyist can communicate about this circuit without knowing each other's language. Once again, an international standard notation has come to the rescue. Only this time it is not purely mathematical; the objects in the diagram have real physical instantiations. Moreover, semantics is in play: Not only is Ohm's Law implied, but also implied is the direction of current flow that comes from our notions of the positive and negative terminals of the battery, represented by the long and short horizontal lines. I typically spend a few moments on the richness of the information communicated by this simple diagram, and remark how hard it would be to do any electrical engineering at all if we didn't have this notation that is the same all over the world.

Incidentally, I have moved the accessibility threshold up to anyone having had one year of introductory physics.




The Software Development Edge(c) Essays on Managing Successful Projects
The Software Development Edge(c) Essays on Managing Successful Projects
ISBN: N/A
EAN: N/A
Year: 2006
Pages: 269

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