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resistance of a wire
I know that the thicker the wire, the less reisstance produced but what i don't get is why, because there is more room but more stuff in that more room to get in the way of the eletric current.
can someone explain it please?
can someone explain it please?
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The electrons that make up the current travel through the wire from atom to atom. Imagine that the electrons are people crossing a stream on stepping stones, where the stepping stones represent the atoms. The more rows of stepping stones you place over the stream, the more people can cross at the same time. i.e.the thicker the wire, the more electrons can move through it at the same time = more current.
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"And they move at 186,000 miles per second, knocking on a bit. "
Actually the electrons move down the wire at a speed as low as a few centimetres a hour, but despite that slow speed the effect of applying a charge at one end of a wire is seen at the other end of the wire almost instantly. think of it like a pipe full of marbles, if you push one more marble into one end of the pipe then, as the pipe is already full of marbles a marble will pop out the other end almost instantly even though each marble has only moved a tiny bit and slowly.
Actually the electrons move down the wire at a speed as low as a few centimetres a hour, but despite that slow speed the effect of applying a charge at one end of a wire is seen at the other end of the wire almost instantly. think of it like a pipe full of marbles, if you push one more marble into one end of the pipe then, as the pipe is already full of marbles a marble will pop out the other end almost instantly even though each marble has only moved a tiny bit and slowly.
"And they move at 186,000 miles per second, knocking on a bit."
As ChuckFickens said, it's not that the electrons move at that speed. Under Einstein's Relativity, it is technically impossible for an object with mass to achieve light speed. It is actually the electric FIELD that travels down the wire at 186,000 miles/second.
I could very well be wrong as it has been a while, but I am pretty sure the atoms do NOT travel from atom to atom. They travel in the spaces between the atoms - a material that can conduct electricity has lots of electrons loosely bound to its nucleus so under certain conditions (like an electric field) they can move freely and travel about in the spaces between atoms. This is a classical description, so there could very well be a different quantum description.
As for resistance, they way it was kind of explained to me is,for a given voltage over a wire, the electrical field will try and push a certain number of electrons each second along the wire, regardless of how thick the wire is. An analogy would be trying to push a given number of women (i.e. electrons) per second along a corridor. The corridor has already got a number of men per sq metre standing around in it doing nothing (i.e. atoms). If the corridor is narrow then it it is difficult for the women to get past without jostling against the men and other women, creating heat. If the corridor is very wide then it is much easier for the same amount of women to get though without jostling, therefore less heat.
As ChuckFickens said, it's not that the electrons move at that speed. Under Einstein's Relativity, it is technically impossible for an object with mass to achieve light speed. It is actually the electric FIELD that travels down the wire at 186,000 miles/second.
I could very well be wrong as it has been a while, but I am pretty sure the atoms do NOT travel from atom to atom. They travel in the spaces between the atoms - a material that can conduct electricity has lots of electrons loosely bound to its nucleus so under certain conditions (like an electric field) they can move freely and travel about in the spaces between atoms. This is a classical description, so there could very well be a different quantum description.
As for resistance, they way it was kind of explained to me is,for a given voltage over a wire, the electrical field will try and push a certain number of electrons each second along the wire, regardless of how thick the wire is. An analogy would be trying to push a given number of women (i.e. electrons) per second along a corridor. The corridor has already got a number of men per sq metre standing around in it doing nothing (i.e. atoms). If the corridor is narrow then it it is difficult for the women to get past without jostling against the men and other women, creating heat. If the corridor is very wide then it is much easier for the same amount of women to get though without jostling, therefore less heat.
It's the valence electrons of an element which determines its electrical conductivity:-
http://en.wikipedia.org/wiki/Valence_electron
Scroll down to "Valence electrons and electrical conductivity"
http://en.wikipedia.org/wiki/Valence_electron
Scroll down to "Valence electrons and electrical conductivity"
In fact, the field propagates down all conductors at a speed less than c. http://en.wikipedia.o...ave_propagation_speed
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