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RE: voltmeter reading (was: cheap 90 amp alternator fix)
The Impedance/resistance of a conductor (external wiring as well as the
windings inside the alternator ) will increase with heat. According to
Ohms Law: Voltage (V) = Current(I) * Resistance(R). If the resistance
in a section of wire goes up so does the voltage drop across that
section. This is also why superconductors are usually cooled with
fluids such as liquid nitrogen and others.
>From: firstname.lastname@example.org [SMTP:email@example.com]
>Sent: Friday, March 06, 1998 9:22 AM
>Subject: voltmeter reading (was: cheap 90 amp alternator fix)
>Speaking of alternators, I have a question.
>My 4000 (which has a 90A alt) voltmeter would show about 13V when the
>car is started first time in the morning, and after warming up the reading
>would drop to about 12V or so. I know that the voltmeter is reading a bit
>low due to the ground arrangement as well as the voltage drop across
>the various wiring and connectors, but why would the reading drop over time?
>In comparison, my A4's voltmeter would read a bit over 14V pretty
>much all the time...
>96 A4 2.8 quattro
>84 5000S 2.1 turbo
>80 4000 2.0
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