Re: How do relays work?

[JJK1204@domain.elided]

In a message dated 7/13/99 9:02:15 AM Central Daylight Time, 
Andrew.Watry@domain.elided writes:

<< Relays are prescribed as the fix for a number of electrical ills, 
especially
 where there seems to be a voltage drop over a long distance.   Along with
 helping out Spica pump solenoids and the like, I just read that relays were
 a standard fix in the 60s for weak headlights on 6-volt VWs and Porsche
 356s.  How do relays work?  Seems to me like getting something for nothing
 or pulling yourself up by your bootstraps. How do you get better voltage
 going out than coming in?
 
 Andrew Watry >>

A relay is composed, in most common automotive applications, of an 
electromagnetic coil, which when energized, moves an electrically conductive 
plate which completes the main circuit, thus it is basically a remotely 
actuated knife switch (like the ones used to turn on power in horror movies 
like Frankenstein).There are two advantages to relays. First, they can reduce 
the distance that the working electric current must travel, thereby reducing 
the voltage drop over distance. (Voltage drop over distance is why you need a 
heavier cable when you mount your battery in the trunk.) Second, they can 
switch a larger wire than is practical in a standard switch. They don't 
really give better voltage going out than coming in, they simply are a remote 
control so that the voltage drop from distance and wire gauge are minimized.

John Katos 

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