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Re: Stupid question
Chris,
I have cornered the market on stupid questions and will tolerate no
competition. Long
ago I was lucky enuff to have a great teacher who told us that the only
stupid question is
the one not asked. The word here is "serendipity." It means seeing a question
to be asked or a problem to be solved when all others are unable to see that
the question or a problem even exists. Only those who ridicule are behaving
stupidly.
Whenever you get confused about the electrical units, you may find it helpful
to see what
the dimensions of the unit are. A Volt is a Joule/Coulomb and an Ampere is a
Coulomb/second. Treat the dimensions as you do the actual numbers, i.e., the
dimensions are subject to the same math rules as are the numbers. This is
called dimensional analysis.
>From Ohm's Law:
P=EI
=Joules/Coulomb x Coulombs/second (Coulombs cancel)
P=Joules/second
(1 J/s = 1 Watt.) The Joule is a unit of energy, energy divided by time is
the rate of using
energy. That's the power. The unit of power is the Watt.
Also, and I think this may be the source of your original question: (remember
the ??)
P=EI but E=IR.
So by substitution:
P=(E)I
=(IR)I
P=I squared R
so EI (volts x Amps) = I^2 R (I squared R)
You can substitute the units to see that the dimensional analysis is
perfectly consistent.
I would suggest that even if you are still in grammar school, you should
visit a high school physics teacher and try to schmooze him out of a physics
text. The physics text will show you a lot about units and dimensional
analysis.
Keep asking those stupid questions.
Ralph Zekelman