Voltage, Current, Resistance definitions


by mtanti
Tags: current, definitions, resistance, voltage
mtanti
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#1
Dec5-06, 03:01 PM
P: 172
Can someone please give a straight forward and easy to understand definition of the 3 mentioned phenomenone in terms of electrons if possible?
Thanks!
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chroot
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Dec5-06, 03:05 PM
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Voltage is directly related to the force electrons feel in a wire. This force propels them through the wire. You can think of voltage (more correctly expressed as a difference in electrical potential) as an analogy to water pressure in a pipe. The pressure is what causes water to flow out of your tap, for example.

Current is a measure of the number of electrons that pass through some given point in a wire per unit time. The larger the current, the more electrons flow through the wire per unit time.

Resistance is caused by a material's interaction with electrons. Some material inhibit electrons from moving quickly through them, in the same way that a sponge shoving into your water faucet would inhibit the flow of water.

- Warren
mtanti
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Dec5-06, 03:09 PM
P: 172
So voltage is the amount of energy in each electron and current is the speed of the electrons whilst resistance is the multiple of speed reduced from the electrons?

chroot
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Dec5-06, 03:26 PM
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Voltage, Current, Resistance definitions


Yes, voltage is related to the kinetic energy of each electron. An electron moving through a potential difference of 100 volts gains twice as much kinetic energy as an electron moving through a potential difference of 50 volts.

Current, however, is not related to speed. You can have a large number of very slow electrons passing some point in a wire, or a smaller number of very fast electrons, and the current will be the same. Keep in mind that the actual speed of electrons in wires -- the speed they move from one terminal of a battery to another, for example -- is quite slow. You should not worry much (at this point) about speed at all.

Resistance is not so much a process of slowing electrons down as it is a process of stripping them of kinetic energy and turning that energy into heat. Certainly, you can't reduce kinetic energy without reducing speed, but it's much simpler to view resistance as a phenomenon of energy rather than speed.

- Warren
es1
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#5
Dec6-06, 12:34 AM
P: 324
The traditional, easy to understand, definition involves the water analogy.
Here is a good presentation of it.
http://hyperphysics.phy-astr.gsu.edu...ic/watcir.html

Please don't take it too far though. Once you have the inituitive understand change to thinking in energies, as chroot suggests.


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