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Old 04-30-2008, 11:48 PM
supriyayerra supriyayerra is offline
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Default Is earth a conductor or insulator

I wanted to know whether is a conductor or insulator,and in what conditions
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Old 05-01-2008, 12:08 AM
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Originally Posted by supriyayerra View Post
I wanted to know whether is a conductor or insulator,and in what conditions
Earth can conduct electricity but not as good a wires. Its resistance depends on the kind of the ground , how far is one point from the other where you measure the resistance, the moisture, and other factors. Search in google to find more specific answers.
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Old 05-01-2008, 01:22 AM
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I have to agree with the conductor assessment. Earth is used as a reference for most voltages, even when it isn't acually used. It is where the term ground came from.
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Old 05-03-2008, 10:49 PM
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I disagree with the conductor assessment :P

Earth, since it is an extremely large connected mass, will not build up a charge very easily. Earth has an electric potential of zero, since there is no charge. This is why circuits are referenced to earth. In order for there to be a conductor, you need a many free ions, which it does not have.

Steve
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Old 05-03-2008, 11:54 PM
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beenthere beenthere is offline
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The earth does have many free ions (possibly you meant to say electrons). Its ability to conduct makes it possible to use it as a measurement reference. In the first years of telegraphy, the earth was used as the conductor that completed the energizing circuit.

Your assessment of the earth's potential being zero is a measure of conductivity. If it weren't conductive, potential would build up in areas and cause lightening-like discharges.
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Old 05-04-2008, 12:59 AM
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There may be spots where conductivity isn't as good as others, but in whole the earth is a big chunk of iron, with a salty water and slime coating. We do get lightning, but the charge has to conduct for it to occur. It is significant that most lightning is generated in the atmosphere.

Don't think it's conductive? Go stand outside in your bare feet and hold a hot wire. But before you do make funeral arrangements.

If the net charge is zero where do you think the magnetic field comes from? We have a significant one.
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Old 05-04-2008, 08:42 AM
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Quote:
big chunk of iron
Well yes there is some iron but also even more aluminium. Nevertheless it depends upon the state of the substance.
Metallic aluminium is one of the best conductors. Aluminium oxide on the other hand is one of the best insulators.

Most iron and aluminium occurs as oxide.

The original poster also asked about conditions. The truth is of course much more complex.

Conductors are normally those substances which have close or even overlapping occupied and empty valence bands of electrons.
Insulators have widely separated bands.

Textbooks consider pure substances when considering this question. And relatively small samples of these substances. So the valence bands stretch uninterrupted from one end of the sample to the other.

The Earth, on the other hand, is an extremely non homogenous large mixture. This mixture contains many internal and surface conducting paths which extend a full range of distances from microns to thousands of kilometers.
But you can also draw many paths through and over the surface of the earth which are non conductive.

So yes the Earth is both conductive and non conductive. You can change the conditions by for instance adding water.
A simple example is the cable that wires your house. Is that conductive or non conductive?The copper wire is conductive, the plastic sheath is nonconductive (you hope). If you connect make a connection to the wire at one end and the plastic at the other........

These characteristics are use in geophysical exploration in the form of resistivity surveying using the conduction current and with ground penetrating radar using the displacement current.

Finally the earth - atmosphere system forms a huge capacitor.
The earth's surface forms the lower plate and the so called electrosphere forms the upper plate, charged to about 300,000 volts. The electrosphere extends over the whole globe at about 50 Km up and is formed from conductive ions in the air. It is between this layer and the surface that lightning discharges.
The resultant field can readily be measure by simple instruments and is used in one system of aerial navigation - the Maynard Hill system.

Last edited by studiot; 05-04-2008 at 09:04 AM.
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Old 05-04-2008, 01:19 PM
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For the most part you are talking the crust, especially where aluminum and silicon are concerned. The core is primarily iron, molten but pure, which is where the magnetic field is coming from as I understand it. The surface is also pretty wet, by any standard, even the driest part of this planet have some humidity, unless the temperature is way below freezing.

We may be arguing semantics, but finding a dry land area of earth (which is 1/3 the surface of the planet) that isn't conductive is the exception rather than the rule, by a large extent. I'll stick with my original answer.

Again, you can receive a lethal shock from relatively low voltage systems just through the earth and a hot wire. This is pretty much universal.

I've been reading some interesting articles about Tesla's broadcast power systems that suggest this conductivity, along with the capacitance of the atmosphere (the upper atmosphere is conductive while the lower atmosphere is insulative), is the basis of his broadcast power scheme, which is a major misnomer. It wasn't broadcast at all, at least not through the atmosphere. The earth has a resonance frequency also, which Tesla predicted and has been experimentally verified, of around 7 Hz. If anyone is interested I'll look up the links again.
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Last edited by Bill_Marsden; 05-04-2008 at 01:32 PM.
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Old 06-04-2008, 12:03 PM
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Quote:
Originally Posted by Bill_Marsden View Post
I've been reading some interesting articles about Tesla's broadcast power systems that suggest this conductivity,....The earth has a resonance frequency also, which Tesla predicted and has been experimentally verified, of around 7 Hz. If anyone is interested I'll look up the links again.
I did some reading on this a few months ago. The earth has indeed been proven by Nikola Tesla to be a conductor. You can check this wiki link under the heading 'Colorado Springs' : http://en.wikipedia.org/wiki/Nikola_tesla

Here are some extracts from that link:
"....Tesla's diary contains explanations of his experiments concerning the ionosphere and the ground's telluric currents via transverse waves and longitudinal waves.[62] At his lab, Tesla proved that the earth was a conductor,...."

"....He transmitted extremely low frequencies through the ground as well as between the earth's surface and the Kennelly-Heaviside layer....."
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Old 06-04-2008, 09:10 PM
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The Navy uses that 7 Hz freq to talk to deeply submerged submarines - real slow bit rate, though.
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