At 14:24 +1100 12/11/97, Joe Curry wrote:
>For all the "current flows both directions" or "it doesn't matter"
>partisans out there. If that is so, Please explain to me how diodes
>work!
>
>Dan, Watch what kinds of responses I get!
>
>Joe Curry '63 Spit
To which the only sensible response is "what type of diode?"
[Never answer a question with another question, to which the proper
response is: why not?]
Taking the example of a thermionic (vacuum tube) diode, which is the
easiest to visualize and explain, it consists of two electrodes (metal
plates) sealed in a vacuum tube. The cathode is heated and the anode is
not. The high temperature of the cathode creates high energy electrons
which can escape from the metal of the cathode (sometimes referred to as
"boiling off"). If a voltage is applied to the diode with the cathode
negative and the anode positive, then current will flow through the diode.
If the polarity of the voltage is reversed, there are no high energy
electron at the anode and no current will flow.
I seem to recall that this was how it was determined that current was
carried by negatively charged particles which they then called electrons.
Electron flow in metal conductors is not a theory, it is a fairly well
established fact.
Electricity does not actually flow from one point to another, regardless of
direction, it flows in circles; which, for reasons which escape me, are
called circuits. After an electron flows through the wires from the
negative terminal of the battery to the positive terminal, it then flows
back through the battery to the negative terminal. The proof of this is
startlingly simple. If the electrons all accumulated on the positive
terminal of the battery, our cars would progressively lean to one side,
until eventually they would be undriveable. Positive ground cars would
lean one way and negative ground cars the other.
Regards, Trevor Jordan
74 TR6 CF29281U
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