Re: How to explain what a Tesla coil is....

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 12/11/01 11:34:52 PM Central Standard Time, tesla-at-pupman-dot-com
writes: 


>
> as previously mentioned in another post, water in pipes is a good 
> analogy...   voltage being the water pressure and amperage being the 
> gallons per minute flow and the pipe size being similar to the needed 
> wire size to handle the pressure/flow....   ( garden hose/fire hose 
> both have 60 psi but the fire hose will fill the bucket faster but if 
> you put 500 psi in the extra strong reinforced garden hose and left the 
> fire hose at 60 psi the garden hose will fill the bucket faster)) 



Scot, all, 

The water pressure/ flow is an excellent way to describe the 
voltage/ amperage aspect of electricity. With electricity, in- 
stead of dealing with the flow of water droplets, you're dealing 
with the flow of electrons, where pressure or PSI is the equivalent 
of potential or voltage and flow or gallons per minute is equiva- 
lent to the current or amperage. 

As a professional fire fighter with 13 years on the job, I can cer- 
tainly relate to the GPM/PSI aspect of water flow. However, with 
water flow, figuring out the total water flow as a result of hose di- 
ameter vs. pressure isn't quite as simple as saying a 1/2" hose 
needs twice as much pressure to flow the same GPMs as a 1" 
hose. I'm a little rusty on water flow theory now (it's been 13 years) 
but friction losses inrease logarithmically with the inverse of the 
hose diameter. I'm not too good on math but I think the friction loss 
increases with the 5th power of the inverse of the hose diameter. In 
other words, a 1" diameter hose will have 32 times the friction loss 
and reisitance to water flow as a 2" diameter hose and converse- 
ly, the 2" diameter hose will have 32 less friction loss than the 1" 
hose (2^5=32) The bottom line is that a 1/2" ID garden hose re- 
inforced to withstand 500 PSI still couldn't flow the GPMs that 
a 2.5" ID fire hose flowing at 60 PSI could. 

Now let me stop this before the moderator does as this is begin- 
ning to get way off topic. The bottom line though, is that water flow 
and water pressure are quite analogus to current and voltage 
but you end up opening a can of worms when you try to compare 
water flow and pressure combined to electrical power (watts) :-) 
I guess the hose diameter is comparable to the cross sectional 
area or circular mils of conductors, but cross sectional area only 
increases with the square of the diameter of the conductor (doub- 
ling the diameter quadruples the cross sectional area- (4 times the 
amperage capacity or ampacity). Frictional losses decrease with the 
5th power of the diameter increase of a water hose or pipe (doubling 
the hose diameter decreases the friction losses 32 fold). Obviously, 
it is very advantageous to use only marginally larger diameter hose 
for firefighting purposes to get much more water to the fire. Now I 
hope  this makes sense. 


Ok, let me quit rambling here before I get even furhter off topic :-) 

Sparkin' in Memphis, 
David Rieben