AC vs DC

build up of different charges then discharge. I think there are several theories as to why it actually happens.

where does AC occur naturally?

Also how does a electric eel shock stuff in a tank with no ground probe? I ask because people claim ground probes will make the tank less safe.

 

Effective transmission distance is determined by the amount of voltage drop in a transmission line. Voltage is dropped across resistive and reactive components of the transmission line proportional to the current in the transmission line. DC current will drop less voltage over a given distance than an effective AC current due to the AC voltage drop of the reactive components.

For example, a utility customer requires 35kV. The transmission distance is 500 mi. The AC line drop is 100V. The DC line drop is 30V (these numbers are arbitrary and illustrative only). For AC transmission the utility must provide 35100 V at the source in order for the customer to receive the required 35000 V. For DC transmission the utility must provide 35030 V at the source for the customer to receive the required 35kV.

Therefore DC transmission is more "efficient" than AC transmission...

 

These values were in general arbitrarily chosen back in the day. The first AC transmission station at Niagara Falls used 25 Hz generators. 50 Hz was chose presumably because the Europeans liked "metric" numbers (1,5,10).

It could be argued that Tesla chose 60 Hz due to his ultimate goal of using the Earth to transmit electricity and the correspondence of the frequency with a resonant node of our planet...

 

Because the eel uses it's enviroment as a ground. Polarity is not fixed with DC.

AC naturally occurs between the poles of our planet. It is actually measurable from outerspace. It also occurs with in the bodies of certain life forms.

Lighting (presently believed) occurs due to a static charge build up between the earth and it's atmosphere, when great enough, it let's loose this energy in the form of lighting- in all known cases, this flow of electricity is from the earth to the atmosphere- another words "from the ground up".

 

I thought DC had constant polarity since it flows in one direction.

 

Again I disagree- are we not comapring apples to apples here?

In order to first transmit equal voltages over equal distances the media required to do such for DC is considerably greater then that of AC, this is simply due to the resistive load of the media itself. Therefore the potential energy of an AC derived source becomes much more usuable over a greater distance due to a lesser resistive load propensity- given equal media.

 

Nope, and that is why for example, you can test this yourself, it's about the magnetic field that is created with concern to DC- take a speaker and hook a D sized battery to it in the correct fashion- possitive to possitive and negitive to negitive- the speaker will move in an outward fashion- now reverse the leads- the speaker will now move in the reverse- the reason for this is that the magnetic field that is reqired for electricity to exist (in this case) in has been reversed. This is polarity shift- the earth does this very same thing. This is why it is "believed" that DC flows from possitive to negitive- to my knowledge it has never been actually proven- I think it's justa prefered standard that is used to keep everyone on the same "playing field"- so to speak. Either way- it is still flowing in only one direction.

BTW, odd how science has proven that lighting flows from the earth (ground) to the atmosphere- odd.

 

But we don't up the voltage, we control reactive power with cat banks and VAR control. DC is more efficient at transmitting power. However... the "distribution" of AC is much more easier to supply varied voltages. Back in the day it was much easier to use AC to supply power in small areas. They never set up the grid we have today to ship power from the East coast to the West. It was a local grid that just kept getting built upon and here we are. We have some large transmission lines across the U.S. that might have been bette rid they were DC... we have some DC lines too, but the line loss is acceptable. We only loose 6-7% over the grid.

 

Thanks powerman- see even I am learning from you- I didnt know all of that.