Date: Thu, 15 Apr 2004 12:48:42 -0400

Author: "Brad Shue"

Subject: RE: Temperature-Spectrum demo

Post:

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Tappers,
The lamp dimmer switch uses a triac to clip the 60 Hz so that you never
fully energize the lamp. The control just sets the clipping voltage. Now a
ceiling fan dimmer might work because I think it maintains the full 60 Hz
wave or smoothes it out somewhat instead of chopping it abruptly. Anyone
who has tried using a lamp dimmer on a ceiling fan knows the BUZZ it will
give from the clipping not to mention the inductive feedback from the motor
that will travel all over your house circuits as noise. Yes, I made this
mistake before and burned out the dimmer and the fan was not happy with me
either.

Brad Shue
123 Idlebrook Rd
Statesville, NC 28677
704-528-7518
704-528-1084 FAX
-----Original Message-----
From: owner-tap-l@listproc.appstate.edu
[mailto:owner-tap-l@listproc.appstate.edu]On Behalf Of Roger Key
Sent: Thursday, April 15, 2004 10:55 AM
To: tap-l@listproc.appstate.edu
Subject: Re: Temperature-Spectrum demo


At 09:47 AM 4/15/2004 -0500, you wrote:

Have you tried a simple dimmer switch? Seems like the variac, being a
inductive thingy might not give you the right control for a resistive load.
(I should have stayed awake in my EE course.)


I have both the variac and the dimmer with socket in a small box - the
latter is lighter for road shows, but does not show the low end of the
energy spectrum as well, as it seems to have a "threshold" of some kind
before it will light the bulb - I'm using a straight filament 40 or 60 watt
bulb. Anyone care to speculate why it would work that way?

- Roger Key


Paul

On Thursday, April 15, 2004, at 09:28 AM, Matt Lowry wrote:


Howdy Tappers,

I recall seeing last year in Madison a demo whereby someone set up a
light bulb and varied the current to it. We then looked at the
continuous spectrum while the current was decreased. As the current
(and temperature of the filament) dropped, you could see the higher
energy blue light (and then green, etc) fall out of the spectrum.

Nice demo to show higher frequency light is more energetic.

Who did that demo? I'm trying to set something similar up with a
Variac, but - no kidding - I'm having a devil of a time getting it to
work. I'm wondering if the bulb puts too much load on the output of
the
Variac, and if so, what to do about it.

Cheers,

Matt Lowry
Lake Forest HS
Lake Forest, IL

=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=
Roger Key rogerk@csufresno.edu
California State University, Fresno phone 559-278-2728
Department of Physics MH#37 paper fax 559-278-7741
2345 E San Ramon Ave
Fresno CA 93740-8031

"It's not the mountain you face that wears you out,
it's the grain of sand in your shoe"

Physics Department Web Page: http://physics.csufresno.edu
Downing Planetarium Web Page: http://www.Downing-Planetarium.org
Physics Instructional Resource Association: http://www.pira.nu


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size=3D2>Tappers,

size=3D2>The=20
lamp dimmer switch uses a triac to clip the 60 Hz so that you never =
fully=20
energize the lamp.  The control just sets the clipping =
voltage.  Now a=20
ceiling fan dimmer might work because I think it maintains the full 60 =
Hz wave=20
or smoothes it out somewhat instead of chopping it abruptly.  =
Anyone who=20
has tried using a lamp dimmer on a ceiling fan knows the BUZZ it will =
give from=20
the clipping not to mention the inductive feedback from the motor that =
will=20
travel all over your house circuits as noise.  Yes, I made this =
mistake=20
before and burned out the dimmer and the fan was not happy with me=20
either.


size=3D2>
 

Brad Shue
123 Idlebrook Rd
Statesville, NC=20
28677
704-528-7518
704-528-1084  FAX


face=3DTahoma=20
size=3D2>-----Original Message-----
From:=20
owner-tap-l@listproc.appstate.edu=20
[mailto:owner-tap-l@listproc.appstate.edu]On Behalf Of Roger=20
Key
Sent: Thursday, April 15, 2004 10:55 AM
To:=20
tap-l@listproc.appstate.edu
Subject: Re: =
Temperature-Spectrum=20
demo

At 09:47 AM 4/15/2004 -0500, you wrote:

Have you tried a =
simple dimmer=20
switch?  Seems like the variac, being a inductive thingy might =
not give=20
you the right control for a resistive load.  (I should have =
stayed=20
awake in my EE course.)

I have both the variac =
and the=20
dimmer with socket in a small box - the latter is lighter for road =
shows, but=20
does not show the low end of the energy spectrum as well, as it seems =
to have=20
a "threshold" of some kind before it will light the bulb - I'm using a =

straight filament 40 or 60 watt bulb.  Anyone care to speculate =
why it=20
would work that way?

- Roger Key


Paul

On =
Thursday, April=20
15, 2004, at 09:28  AM, Matt Lowry wrote:


Howdy =
Tappers,

I recall=20
seeing last year in Madison a demo whereby someone set up =
a
light bulb=20
and varied the current to it.  We then looked at =
the
continuous=20
spectrum while the current was decreased.  As the =
current
(and=20
temperature of the filament) dropped, you could see the =
higher
energy=20
blue light (and then green, etc) fall out of the =
spectrum.

Nice=20
demo to show higher frequency light is more energetic.

Who =
did that=20
demo?  I'm trying to set something similar up with =
a
Variac, but -=20
no kidding - I'm having a devil of a time getting it =
to
work.  I'm=20
wondering if the bulb puts too much load on the output of =
the
Variac,=20
and if so, what to do about it.

Cheers,

Matt =
Lowry
Lake=20
Forest HS
Lake Forest, =
IL

   =20
=
=3D+=3D+=3D+=3D+=3D+=3D+=3D+=3D+=3D+=3D+=3D+=3D+=3D+=3D+=3D+=3D
 =
            &=
nbsp;           =20
Roger=20
=
Key           &nbs=
p; =20
rogerk@csufresno.edu
California State University,=20
=
Fresno           &=
nbsp;   =20
phone 559-278-2728
        =
Department of=20
Physics=20
=
MH#37            =
paper=20
fax=20
=
559-278-7741
         &nb=
sp;    =20
2345 E San Ramon=20
=
Ave           &nbs=
p;   =20
=

           &nb=
sp;  =20
Fresno CA=20
=
93740-8031          &nb=
sp;    =20


"It's not the =
mountain you face=20
that wears you out,
it's the grain of sand in your=20
shoe"

Physics Department Web=20
=
Page:           &n=
bsp;=20
eudora=3D"autourl">http://physics.csufresno.edu
Downing =
Planetarium Web=20
Page:      href=3D"http://www.downing-planetarium.org/"=20
eudora=3D"autourl">http://www.Downing-Planetarium.org
Physics=20
Instructional Resource =
Association:       =20
=
eudora=3D"autourl">http://www.pira.nu

>

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From reberg@physics.umd.edu Thu Apr 15 12:59:42 2004

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