| Topic: |
Science > Physics |
| User: |
"gubernacullum" |
| Date: |
09 Dec 2005 04:30:02 AM |
| Object: |
physics1012707 |
what is the relationship between the amount of current input and light
emission from a conductor? is there a minimum and maximum threshold
level of current beyond which no light is emitted? what is the
difference between a direct and alternating current in this case?
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| User: "Dave" |
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| Title: Re: physics1012707 |
09 Dec 2005 01:34:16 PM |
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are you talking about light as in from a hot wire or lamp filament??
"gubernacullum" <gubernacullum@yahoo.com> wrote in message
news:1134124202.343329.108920@o13g2000cwo.googlegroups.com...
what is the relationship between the amount of current input and light
emission from a conductor? is there a minimum and maximum threshold
level of current beyond which no light is emitted? what is the
difference between a direct and alternating current in this case?
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| User: "PD" |
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| Title: Re: physics1012707 |
09 Dec 2005 01:40:16 PM |
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gubernacullum wrote:
what is the relationship between the amount of current input and light
emission from a conductor?
Depends on details of shape and material of conductor.
is there a minimum and maximum threshold
level of current beyond which no light is emitted?
No. Although not much light may be in the *visible* spectrum for some
values of current.
what is the
difference between a direct and alternating current in this case?
In which case?
PD
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| User: "gubernacullum" |
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| Title: Re: physics1012707 |
09 Dec 2005 04:40:17 PM |
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hi,
assume a long copper wire connected first to a dc supply and then to an
ac supply. is it not true that there would be a minimum and maximum
frequency of light produced in each case? does this not demonstrate the
limited range of frequencies with which natural and artificial light
permeates through the universe?
.
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| User: "Dave" |
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| Title: Re: physics1012707 |
09 Dec 2005 05:47:11 PM |
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"gubernacullum" <gubernacullum@yahoo.com> wrote in message
news:1134168017.159960.118030@z14g2000cwz.googlegroups.com...
hi,
assume a long copper wire connected first to a dc supply and then to an
ac supply. is it not true that there would be a minimum and maximum
frequency of light produced in each case? does this not demonstrate the
limited range of frequencies with which natural and artificial light
permeates through the universe?
no, it produces a broad spectrum according to blackbody radiation laws. even
a wire carrying a low current produces electromagnetic radiation, its just
mostly at too low a frequency for you to see with your eye. and when it
does get hot enough for you to see it, it is still producing the low
frequency stuff, but even more at higher frequencies that you can see as
'light'. and the hotter it gets the higher that frequency peak moves... at
least until the wire melts.
.
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| User: "gubernacullum" |
|
| Title: Re: physics1012707 |
10 Dec 2005 12:15:31 AM |
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From: "Dave" <n...@nowhere.com>
Newsgroups: sci.physics,sci.physics.electromag
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<1134168017.159960.118030@z14g2000cwz.googlegroups.com>
Subject: Re: physics1012707
Date: Fri, 9 Dec 2005 23:47:11 -0000
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"gubernacullum" <gubernacul...@yahoo.com> wrote in message
news:1134168017.159960.118030@z14g2000cwz.googlegroups.com...
hi,
assume a long copper wire connected first to a dc supply and then to an
ac supply. is it not true that there would be a minimum and maximum
frequency of light produced in each case? does this not demonstrate the
limited range of frequencies with which natural and artificial light
permeates through the universe?
no, it produces a broad spectrum according to blackbody radiation laws.
even
a wire carrying a low current produces electromagnetic radiation, its
just
mostly at too low a frequency for you to see with your eye. and when
it
does get hot enough for you to see it, it is still producing the low
frequency stuff, but even more at higher frequencies that you can see
as
'light'. and the hotter it gets the higher that frequency peak
moves... at
least until the wire melts.
-----------------------------------------------------------------------------------------------------------------------------------
i was trying to determine the mechanism of light production. with a dc
supply, the coductor would get hot and incandesce producing photons of
various frequencies up to its melting point. however, the conductor
will also generate an electromagnetic field. this field has a range
related to the voltage applied to the conductor. another conductor
moving through this field will experience induction and generate
electricity. if the first conductor is switched on and off, this will
generate an em wave which will induce current in the second conductor.
i am trying to determine wether a dc current or an ac current will
generate light more efficiently for communication purposes. and is the
range of frequencies produced not limited by the melting point of
materials? what is the lowest and highest frequencies currently
possible? also, if the range of the electric field is limited by
voltage then how are em waves broadcast over infinite distances of
space?
thanks.
.
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| User: "Dave" |
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| Title: Re: physics1012707 |
10 Dec 2005 07:02:16 AM |
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"gubernacullum" <gubernacullum@yahoo.com> wrote in message
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From: "Dave" <n...@nowhere.com>
Newsgroups: sci.physics,sci.physics.electromag
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<1134168017.159960.118030@z14g2000cwz.googlegroups.com>
Subject: Re: physics1012707
Date: Fri, 9 Dec 2005 23:47:11 -0000
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"gubernacullum" <gubernacul...@yahoo.com> wrote in message
news:1134168017.159960.118030@z14g2000cwz.googlegroups.com...
hi,
assume a long copper wire connected first to a dc supply and then to an
ac supply. is it not true that there would be a minimum and maximum
frequency of light produced in each case? does this not demonstrate the
limited range of frequencies with which natural and artificial light
permeates through the universe?
no, it produces a broad spectrum according to blackbody radiation laws.
even
a wire carrying a low current produces electromagnetic radiation, its
just
mostly at too low a frequency for you to see with your eye. and when
it
does get hot enough for you to see it, it is still producing the low
frequency stuff, but even more at higher frequencies that you can see
as
'light'. and the hotter it gets the higher that frequency peak
moves... at
least until the wire melts.
-----------------------------------------------------------------------------------------------------------------------------------
i was trying to determine the mechanism of light production. with a dc
supply, the coductor would get hot and incandesce producing photons of
various frequencies up to its melting point. however, the conductor
will also generate an electromagnetic field. this field has a range
related to the voltage applied to the conductor. another conductor
moving through this field will experience induction and generate
electricity. if the first conductor is switched on and off, this will
generate an em wave which will induce current in the second conductor.
i am trying to determine wether a dc current or an ac current will
generate light more efficiently for communication purposes. and is the
range of frequencies produced not limited by the melting point of
materials? what is the lowest and highest frequencies currently
possible? also, if the range of the electric field is limited by
voltage then how are em waves broadcast over infinite distances of
space?
thanks.
first, an electromagnetic field is not limited by voltage or current, it
propagates outward forever at the speed of light. only the magnitude is
controlled by the current and voltage. the way the electromagnetic waves
are started by the current in the wire is much different than the
incandescent black body radiation, but the resulting waves once they leave
the wire propagate and interact with other materials exactly the same way.
as for the difference between ac and dc in generating heat in the wire,
there is no difference unless the wire is very thin or the frequency of the
ac is very low in which case you will generate a pulsing light as the wire
heats and cools as the current changes.
.
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| User: "operator jay" |
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| Title: Re: physics1012707 |
10 Dec 2005 09:35:29 AM |
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"Dave" <noone@nowhere.com> wrote in message
news:4vudneVigfx-TAfenZ2dnUVZ_sWdnZ2d@crocker.com...
first, an electromagnetic field is not limited by voltage or current, it
propagates outward forever at the speed of light. only the magnitude is
controlled by the current and voltage. the way the electromagnetic waves
are started by the current in the wire is much different than the
incandescent black body radiation, but the resulting waves once they leave
the wire propagate and interact with other materials exactly the same way.
as for the difference between ac and dc in generating heat in the wire,
there is no difference unless the wire is very thin or the frequency of
the
ac is very low in which case you will generate a pulsing light as the wire
heats and cools as the current changes.
With a thick wire and high frequency you may have more luck heating the
surface thanks to skin effect.
j
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| User: "Don Kelly" |
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| Title: Re: physics1012707 |
10 Dec 2005 08:47:08 PM |
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----------------------------
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Subject: Re: physics1012707
Date: Fri, 9 Dec 2005 23:47:11 -0000
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"gubernacullum" <gubernacul...@yahoo.com> wrote in message
news:1134168017.159960.118030@z14g2000cwz.googlegroups.com...
hi,
assume a long copper wire connected first to a dc supply and then to an
ac supply. is it not true that there would be a minimum and maximum
frequency of light produced in each case? does this not demonstrate the
limited range of frequencies with which natural and artificial light
permeates through the universe?
no, it produces a broad spectrum according to blackbody radiation laws.
even
a wire carrying a low current produces electromagnetic radiation, its
just
mostly at too low a frequency for you to see with your eye. and when
it
does get hot enough for you to see it, it is still producing the low
frequency stuff, but even more at higher frequencies that you can see
as
'light'. and the hotter it gets the higher that frequency peak
moves... at
least until the wire melts.
-----------------------------------------------------------------------------------------------------------------------------------
i was trying to determine the mechanism of light production. with a dc
supply, the coductor would get hot and incandesce producing photons of
various frequencies up to its melting point. however, the conductor
will also generate an electromagnetic field. this field has a range
related to the voltage applied to the conductor. another conductor
moving through this field will experience induction and generate
electricity. if the first conductor is switched on and off, this will
generate an em wave which will induce current in the second conductor.
i am trying to determine wether a dc current or an ac current will
generate light more efficiently for communication purposes. and is the
range of frequencies produced not limited by the melting point of
materials? what is the lowest and highest frequencies currently
possible? also, if the range of the electric field is limited by
voltage then how are em waves broadcast over infinite distances of
space?
thanks.
You appear to have an ambiguity with respect to current and voltage.
Note that the magnetic field producing induction depends on the current in
the wire, not the voltage applied. Applying a high voltage at DC or low
frequency to an open conductor will not induce a voltage in a parallel
conductor. At higher frequencies capacitive coupling (electric field) will
occur but this is not "induction"
--
Don Kelly @shawcross.ca
remove the X to answer
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