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Let's say we have a 120 Volt AC source

by Evil Bunny
Tags: source, volt
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Evil Bunny
#19
Feb18-11, 10:51 AM
P: 237
Quote Quote by Studiot View Post
You just have to watch nature at work in the heavens to see how wrong this view is. Old Ben Franklin must be turning in his grave.

I think everyone will recognise that you can witness large discharges both between the clouds (poles) and the earth.
You bring up a good point Studiot. Why is it that neither of the poles in our 120 Volt generator have any desire to interact with the earth whatsoever, yet the electrons in that cloud are so excited to get to earth that they ionize the air and we see a bolt of lightning come down and touch the ground?

Is it a matter of voltage? Let's take our suspended generator and crank it up to a million volts instead of just a wimpy 120 volts. Would that arc jump from one pole of the generator to the earth or would it jump from one pole of that generator to the other? I've got my money on the one-pole-to-the-other option. What about you?

Excellent, excellent point! Something I know nothing about but am very interested in... Thank you.

Quote Quote by Studiot View Post
Unlike Arial in the Tempest, electrons do not posess desire, which implies free will and choice.
Naty1
#20
Feb18-11, 10:55 AM
P: 5,632
the OP had a similar question, and people were telling him that since the Earth can sink a LOT of charge without changing its potential, it could be very dangerous for a person to touch the positive terminal of a high voltage power supply. That person would be providing a path to ground for current, and the voltage across him would be maintained. Since the charges don't "pile up", there is no build up of an electric field to cancel out the one driving the current. In other words, there is no equalization of potential (this being the reason why current normally won't flow if there isn't a closed circuit).

Are they wrong?
Extremely high voltages have their own "set of rules"...try reading about lightning for example. I was recently told by a power company linesman they can use fiberglas poles up to something like 7,500 volts....don't quote me on that figure.....so current might flow through their bodies otherwise...."What about 25,000 volts and even 250,000 volts...I asked" "how do you work on that"...answer...." You have to shut the power off....
Naty1
#21
Feb18-11, 10:58 AM
P: 5,632
Take a dry cell battery as an example....1.5volts or maybe a 9 volt....touch one terminal the earth...even a car battery....12 volts....what happens??

nothing.

Now take wires stuck into the earth...say wet earth and not too far apart....and touch them to the battery terminals....sparks almost certainly.....current FLOWS....
Naty1
#22
Feb18-11, 11:00 AM
P: 5,632
Try reading here:
http://en.wikipedia.org/wiki/Van_de_Graaff_generator

Note that a sphere holds electric hcarge quite well...one reason lightning arrestors...designed to AVOID charge build yup are typically pointed or wire brush like...to dissipate leader charges as quickly as possible.
Naty1
#23
Feb18-11, 11:06 AM
P: 5,632
Bunny:
I ventured into a physics forum and everyone here is waaaay smarter than me

not likely....more experienced, perhaps....

Never think some else is smarter just because they understand something they have thought about and studied and you are just learning....
JaredJames
#24
Feb18-11, 11:07 AM
P: 3,387
Quote Quote by mquirce View Post
People. be patient uith a ignorant lay man.
I have a question about static electrisity and Plank quanta "h'
Let supose we have two electric unity charges far from each other 3.48181805*10^7 cm in static standing. The potential enrgy of these two charges will be E = h/1 erg.
Now let supose that distance is plus 10 cm longer. I am confused about dilema:
will be energy E< h/1 or will be 0 ?
Please somebody help!
You need to post this in a new thread, not hijack someone elses.
Studiot
#25
Feb18-11, 11:31 AM
P: 5,462
Is it a matter of voltage? Let's take our suspended generator and crank it up to a million volts instead of just a wimpy 120 volts. Would that arc jump from one pole of the generator to the earth or would it jump from one pole of that generator to the other? I've got my money on the one-pole-to-the-other option. What about you?
I thought my poetic cloud example would make it clear that both would likely occur.

Sorry if this was not clear.
Evil Bunny
#26
Feb18-11, 11:39 AM
P: 237
Quote Quote by Studiot View Post
I thought my poetic cloud example would make it clear that both would likely occur.

Sorry if this was not clear.
That's ok. No problem. Can you explain? I think if we slowly increase the voltage until it reaches a point to where an arc would form, this arc would travel from one pole to the other.

Are you saying that when this arc occurred, it would jump from one pole to the other and the ground simultaneously?

I would tend to disagree with that hypothesis, but I bet we could test this one out easy enough.
JaredJames
#27
Feb18-11, 11:46 AM
P: 3,387
Quote Quote by Evil Bunny View Post
Are you saying that when this arc occurred, it would jump from one pole to the other and the ground simultaneously?

I would tend to disagree with that hypothesis, but I bet we could test this one out easy enough.
I don't believe he said that.

The arc would go either from pole A to pole B or from pole A to the ground (assuming pole A is the one the charge built on).
Naty1
#28
Feb18-11, 11:47 AM
P: 5,632
Let's take our suspended generator and crank it up to a million volts instead of just a wimpy 120 volts. Would that arc jump from one pole of the generator to the earth or would it jump from one pole of that generator to the other?
In general, it will arc along the shortest air path...The voltage in a spark plug, for example, can arc the 1/16" or so of separation between the electrodes.....won't go six feet, for example....

When the air ionizes, electrical current beginns to flow.....you'll possibley smell ozone, a product of the ionization....I think it's pretty much the same as cornoa breakdown:


http://en.wikipedia.org/wiki/Electri...rona_breakdown


Partial breakdown of the air occurs as a corona discharge on high voltage conductors at points with the highest electrical stress. As the dielectric strength of the material surrounding the conductor determines the maximum strength of the electric field the surrounding material can tolerate before becoming conductive, conductors that consist of sharp points, or balls with small radii, are more prone to causing dielectric breakdown. Corona is sometimes seen as a bluish glow around high voltage wires and heard as a sizzling sound along high voltage power lines.
The boldface is mine and supports my prior post....
Studiot
#29
Feb18-11, 11:54 AM
P: 5,462
I think Brer Rabbit is trying to play the same game here he plays with Brer Fox and Brer Bear,

Trying to convince them black is white.
Evil Bunny
#30
Feb18-11, 12:07 PM
P: 237
Quote Quote by jarednjames View Post
I don't believe he said that.

The arc would go either from pole A to pole B or from pole A to the ground (assuming pole A is the one the charge built on).
He's not saying much of anything. Which is why I'm trying to get an explanation. I posed a question. Would the arc jump from pole to pole or pole to ground? He said both. I'm trying to guess what he means because he hasn't told us. He was very quick to bring lightning into the conversation as proof of... something? I'm just trying to get to the bottom of why the arc from pole A (for example) would only want to jump to pole B and not to the ground like lightning does. I honestly don't know the answer. Maybe this explanation will help clear things up for me.

Quote Quote by Studiot View Post
I think Brer Rabbit is trying to play the same game here he plays with Brer Fox and Brer Bear,

Trying to convince them black is white.
I'm not trying to convince anyone of anything. I am only trying to get a better understanding of how electricity (whatever that means) works...
JaredJames
#31
Feb18-11, 12:10 PM
P: 3,387
Where did anyone say it would jump to both simultaneously?

The arc will jump through the path of least resistance - this will either be to the other pole or to the ground. There's no more to it than that.
Evil Bunny
#32
Feb18-11, 12:17 PM
P: 237
Quote Quote by Evil Bunny View Post
Let's take our suspended generator and crank it up to a million volts instead of just a wimpy 120 volts. Would that arc jump from one pole of the generator to the earth or would it jump from one pole of that generator to the other?
Quote Quote by Naty1 View Post
In general, it will arc along the shortest air path...
Let's put them the exact same distance apart. Pole B and the earth are now the exact same distance from Pole A. We start increasing the voltage until an arc occurs. The arc originates from Pole A... where does it go?

I say it goes to Pole B even if it was farther away than earth. The "desire" to go to the earth is not there. Correct?

Lightning... on the other hand...
JaredJames
#33
Feb18-11, 12:19 PM
P: 3,387
Quote Quote by Evil Bunny View Post
Let's put them the exact same distance apart. Pole B and the earth are now the exact same distance from Pole A. We start increasing the voltage until an arc occurs. The arc originates from Pole A... where does it go?

I say it goes to Pole B even if it was farther away than earth. The "desire" to go to the earth is not there. Correct?
No. There is absolutely no desire.

As per my previous post, it follows the path of least resistance. (This of course, assumes the ground and pole b are equal in charge.)
Evil Bunny
#34
Feb18-11, 12:21 PM
P: 237
Quote Quote by jarednjames View Post
Where did anyone say it would jump to both simultaneously?
Post #25 except for the "simultaneously" part. Would one happen first? Again... little explanation. Hard to tell.

Quote Quote by jarednjames View Post
The arc will jump through the path of least resistance - this will either be to the other pole or to the ground. There's no more to it than that.
But there is. Didn't we say that there wasn't even a voltage present between the ground and the pole? Why would it ever want to go to the ground in the first place?
JaredJames
#35
Feb18-11, 12:24 PM
P: 3,387
Quote Quote by Evil Bunny View Post
Post #25 except for the "simultaneously" part. Would one happen first? Again... little explanation. Hard to tell.
He said both were likely to happen, not that both would. There is a difference.
But there is. Didn't we say that there wasn't even a voltage present between the ground and the pole? Why would it ever want to go to the ground in the first place?
There is always a potential difference between two points. It's just a matter of how much of a difference.

If the pole is at 1 million volts and the ground is zero (as per your previous post) then there is a potential difference between the ground and the pole.

You may want to go back and learn the basics of electricity.
Evil Bunny
#36
Feb18-11, 12:29 PM
P: 237
Quote Quote by jarednjames View Post
If the pole is at 1 million volts and the ground is zero (as per your previous post) then there is a potential difference between the ground and the pole.
The million volts was between the two poles. 0 volts between pole and ground, remember...


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