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Electricity & EM energy


gaara
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hello

 

im trying to learn the fundamentals of electricity an im stuck already

 

"questions to understand electricity

 

#1 What is the stuff that flows through a light bulb and comes back out again through the other wire?

#2 What is the stuff that flows into a light bulb and gets changed entirely into light and heat? "

 

 

i can understand question 1, its electric charge... bla bla

 

but question 2 i dont get, i can understand where the b field and e fields come from .. but the site im learning from says

 

"THE ENERGY FLOW (POYNTING FIELD):

Electromagnetic energy flows out of the battery and into the empty space around the circuit. It flows parallel to the connecting wires, then it dives into the resistor. The field of energy flow is found by multiplying the e-field by the b-field (E x B vector cross-product.)"

 

So is it the electrons experiencing "friction" in the light bulb's filament that produces heat then light? or is it the EM energy? i dont get it... its too unclear ... an is it also why when you turn on the light it comes on instantly? cause the EM energy is travelling at the speed of light?

 

Ive searched the net for ages about electricity an these EM energy concepts but i cant find anything.. so if anyone konws a site that makes it clear just post the link please!

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hahahah i already read that.

i mentions nothing about EM energy...

 

so from giving me that link.. you are saying there is no EM energy flowing to the light bulb. your saying (the site is saying) the only reason the light lights up is because of the electrons.

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the photon leaving the atom after the electron drops? whats a photon? em energy. or the fact that it just gets really hot and emits light which again is EM energy. it mentions it alright

 

think he is linking light waves (photon) & EM energy, both results.

 

the power to create these or what was originally called ground (2 wire systems) is simple returning this power back to its source, the power company.

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the photon leaving the atom after the electron drops? whats a photon? em energy. or the fact that it just gets really hot and emits light which again is EM energy. it mentions it alright

 

yeah your right it mentions it.. im sorry..

 

What is the stuff that flows into a light bulb and gets changed entirely into light and heat? how stuff works.. doesnt mention anything but the electron input to create the light. an i understand that.. (or maybe i dont.. an thats why im asking stupid questions :) )

 

there are two concepts with electricity.. the electron flow and the other part. can someone explain to me the other part. (ie. the two questions from teh original post)

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yeah your right it mentions it.. im sorry..

 

What is the stuff that flows into a light bulb and gets changed entirely into light and heat? how stuff works.. doesnt mention anything but the electron input to create the light. an i understand that.. (or maybe i dont.. an thats why im asking stupid questions :) )

 

Electrons 'flow' into the light bulb. The reason they flow is a potential difference set up along the circuit by the energy source (battery). Moving electrons create a magnetic field. Look up potential difference on wikipedia.

 

there are two concepts with electricity.. the electron flow and the other part. can someone explain to me the other part. (ie. the two questions from teh original post)

 

Electrons have an electric field, they are effected by other E fields, see wikipedial for potential difference. Moving charges (electrons) create a magnetic field.

 

They will interact with the atoms in the light bulb using the EM fields, they wont actually touch anything as that doesn't really happen. This will result in an energy transfer. This will excite an electron in one of the atoms in the filament, eventually releasing a photon.

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the term is "ohmic heating" the filament is designed to get white hot, hence the tungsten.

 

metals have "delocalised electrons" these are responsible for holding the filament together via electrostatic charge. the voltage causes a few to leave from one end and be replaced at the other.

if you move the electrons, the metal ions will move because the structure shifts slightly.

the electrons do not move in straight lines rather they bounce around interacting with the metal atoms' feilds causing them to move in a random fashion. in kinetic theory, this is called heat.

 

when you heat something up, eventually, the kinetic energy finds it's way into the electron orbitals and is released in the form of a photon when the electron orbital moves back to the ground state.

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ok...

 

my thread.. isnt really supposed to be about lights... its more about the EM energy part....

 

so does EM energy flow from a power source out to all the components of the circuit? ie does the em wave first begin propagating from the power source?

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electrostatic charge, properly known as electromotive force.

like if you have a pipe full of water, you can push water in one end, the pressure builds and some comes out the other end.

if you shove electrons into a wire, the wire gets an electrostatic charge. if you then give the electrons a way out, they will go there.

the electrostatic charge propogates down the wire at the speed of light.

this can also be explained in terms of the hydraulics, if you shove more water into the pipe, the pressure propogates at the speed of sound in water.

except that the speed of sound in the case of electrons is C

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electrostatic charge, properly known as electromotive force.

like if you have a pipe full of water, you can push water in one end, the pressure builds and some comes out the other end.

if you shove electrons into a wire, the wire gets an electrostatic charge. if you then give the electrons a way out, they will go there.

the electrostatic charge propogates down the wire at the speed of light.

this can also be explained in terms of the hydraulics, if you shove more water into the pipe, the pressure propogates at the speed of sound in water.

except that the speed of sound in the case of electrons is C

 

The charge and the force are two separate things. In your analogy, the charge is the water molecule and the force is the pressure/flow of the water. The individual molecule does not have to travel down the hose before water gets out, it only has to move a little, and bump the next one along. It's the bumping that propagates quickly, even though the individual molecules move slowly.

 

In current flow, the drift speed of the electrons is a few mm/sec, but the force they exert propagates at an appreciable fraction of c (c in vacuum, but slower in a wire)

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yeah, charge in culombs, force in volts, i was tired.

 

the electrostatic charge is given by virtual photons (just the same as magnetic feilds) so it does propogate at c

the bumping effect is a given when you use the hydraulic analogy and a charge connected suddenly to a length of cable will propogate immeasurably close to c

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