RE: voltmeter reading (was: cheap 90 amp alternator fix)

["Perry, Christopher" <cperry@cotl.com>]

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.
HTH,
chris perry

>-----Original Message-----
>From:	ti@amb.org [SMTP:ti@amb.org]
>Sent:	Friday, March 06, 1998 9:22 AM
>To:	vw-audisport@worldnet.att.net
>Cc:	quattro@coimbra.ans.net
>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...
>
>-Ti
>96 A4 2.8 quattro
>84 5000S 2.1 turbo
>80 4000 2.0
>-- 
>    ///  Ti Kan                Vorsprung durch Technik
>   ///   AMB Research Laboratories, Sunnyvale, CA. USA
>  ///    ti@amb.org
> //////  http://sunsite.unc.edu/~cddb/tikan/
>///
>