teacher told me that electricity could be defined as "a flow of electrons"


by sanjuro
Tags: a flow of electrons, defined, electricity, teacher, told
sanjuro
sanjuro is offline
#1
Oct5-03, 11:24 AM
P: 10
When I was much younger, my teacher told me that electricity could be defined as "a flow of electrons". So when I turn on a light bulb or television set, what is actually happening inside? What is making the electrons move? A positively charged field perhaps? But how is the field created? Where is it? What is conventional current?

Not challenging questions, but physics is new subject for me.

Thank you
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Sociopath^e
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#2
Oct5-03, 01:42 PM
P: 9
the cell or battery contains electromotive force, or Voltage, this forces the electrons through substances, with resistance against it, thus making current

(i *hope* i'm right here) when it goes through a lightbulb, the electrons heat up the filament, which is supsended in an inert gas, and thus, it glows.
Fuego
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#3
Oct9-03, 10:50 AM
P: 43
'electricity' could be used to describe any phenomena caused by charged particles.

electric current is flow of charge resulting from the movement of charged particles. current is a base quantity, although you could define it as the rate of flow of charge with respect to time. in most cases, an electric current takes the form of a flow of electrons, but a current can also be carried by positive charges (such as the positive charges in an electrolyte).

when you turn on a light bulb (powered by a battery for example), several things happen. by pressing the switch, you complete the circuit. current can only flow in a circuit when the circuit is complete.

the battery has two terminals, positive and negative. the positive terminal is positively charged, and the negative terminal is negatively charged. the difference in charge between the terminals is the potential difference (voltage). the potential difference results in an electromotive force which pushes the elcectrons around the wire. you can think of this as follows: free electrons in the wire are attracted to the positive terminal and repelled by the negative terminal (electrons are negatively charged, opposite charges attract eachother, like charges repel eachother). thus the electrons flow away from the negative terminal and towards the positive terminal.

now that the electrons are moving, there is a current in the wire. the filament in the light bulb has a high resistance. because of the high resistance, the filament heats up a lot when a current is forced through it. the heat energy of the filament is then released (mostly) as light energy.

TVs are quite a bit more complicated. they work by firing beams of electrons onto the screen. there are chemicals in the screen which release light energy when they are excited by the electron beam. i don't think you need to worry any more about this until you have grasped the basics of electricity.

to sum up, the electrons move because of the potential difference between the terminals of the power supply. what's more; the current is directly proportional to the potential difference. if you double the potential difference, you double the current.

conventional current goes from positive to negative. electric current was discovered before the the electron. when they discovered the electron and found that it was negatively charged, they realised that the flow of electrons carrying a current actually went from negative to positive.

mathman
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#4
Oct9-03, 11:28 PM
Sci Advisor
P: 5,935

teacher told me that electricity could be defined as "a flow of electrons"


The elctricity that we have at home or work or school is (with extremely rare exceptions) alternating current, i.e. the electrons are in constant (60 cycles per second in U.S.) back and forth motion, rather than in one direction.
renedox
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#5
Oct10-03, 05:43 AM
P: 29
Originally posted by mathman
The elctricity that we have at home or work or school is (with extremely rare exceptions) alternating current, i.e. the electrons are in constant (60 cycles per second in U.S.) back and forth motion, rather than in one direction.
Yes, the motion is Simple Harmonic.

However, AC current is wildly different from DC.
selfAdjoint
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#6
Oct10-03, 08:57 AM
Emeritus
PF Gold
P: 8,147
I think we have to add here that in metals there are electrons free of their atomic shells, conduction electrons, and these are the physical support for current in wires. The lack of these electrons in non-metals is the reason they don't conduct electricity.


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