Date: Fri, 6 Aug 2010 10:54:50 -

Author: Keith Warren

Subject: Re: 5H15.10 - Field of Wire and Iron Filings

Post:

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Thanks Jerry. I just received my MFJ model 4035 power supply today. I
promptly open the box throwing packing material all over my office. Upon
seeing my excitement, the student who delivered it asked what was in the
box. I grinned really big and said a 30A power supply. He looked at me
like I was a nut and walked out of the door. I took the supply down to the
demo room and hooked it up to the field of a solenoid demo. I could only
find a large 1 ohm resistor laying around. I hooked it up and started to
draw about 12 amps. As I taped the demo, the filings lined up and I smelled
smoke. A quick check showed smoke coming out of the resistor. I laughed at
myself for not checking the power rating of the resistor and put a ballast
resistor on the order list.



Thanks for all the suggestions. This supply should help with many of our
demos.



-Keith

NCSU



From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On
Behalf Of Zani, Gerald
Sent: Friday, July 30, 2010 6:20 PM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] 5H15.10 - Field of Wire and Iron Filings



My experience shows that 15 amp is more than enough. The power supply has a
ballast resistor. I use an MFJ model 4035. It has 30 amp supply and I've
added an external 1/4 Ohm series ballast resistor to limit the current to
30 amps.



http://www.mfjenterprises.com/Product.php?productid=MFJ-4035MV



http://www.physics.brown.edu/physics/demopages/Demo/em/demo/5h1540.htm







On Wed, Jul 28, 2010 at 3:10 PM, Keith Warren wrote:

Hmmm. Now I need a 30A power supply. The best I have is 15A.


-----Original Message-----
From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On
Behalf Of Dale E. Stille
Sent: Wednesday, July 28, 2010 2:41 PM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] 5H15.10 - Field of Wire and Iron Filings

Keith,

If you have a hefty power supply, these that I have built have worked for me
for 25 years. They can also be used with the regular document cameras.
They are 9 inches square and 2.5 inches tall. The plate in the boxes is
raise to the middle so that wiring could be run underneath without being
torn up when storing. This also allows you to catch all the filings and
pour them back into the shaker. One hint, the new OH projectors only allow
you to place that plate in the boxes at less than
2 inches above the glass of the OH before they can't be focused anymore.
See: http://faraday.physics.uiowa.edu/em/5h15.10.htm for pictures.

Oh, the wire used was just solid # 12 we stripped the insulation off of.

Dale



Keith Warren wrote:
> We need to rebuild our field of wire and iron filings demo, 5H15.10.
> Does anybody have a version that works really well?
>
>
>
> -Keith
>
> NCSU
>
>
>






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Thanks =
Jerry. I just received my MFJ model 4035 power supply today. =
I promptly open the box throwing packing material all over my =
office. Upon seeing my excitement, the student who delivered it =
asked what was in the box. I grinned really big and said a 30A =
power supply. He looked at me like I was a nut and walked out of =
the door. I took the supply down to the demo room and hooked =
it up to the field of a solenoid demo. I could only find a large 1 =
ohm resistor laying around. I hooked it up and started to draw =
about 12 amps. As I taped the demo, the filings lined up and I =
smelled smoke. A quick check showed smoke coming out of the =
resistor. I laughed at myself for not checking the power rating of =
the resistor and put a ballast resistor on the order =
list. =
Thanks for =
all the suggestions. This supply should help with many of our =
demos. =
-Keith=
NCSU =
From:=
=
tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On =
Behalf Of Zani, GeraldSent: Friday, July 30, 2010 6:20 =
PMTo: tap-l@lists.ncsu.eduSubject: Re: [tap-l] =
5H15.10 - Field of Wire and Iron Filings My =
experience shows that 15 amp is more than enough. The power supply =
has a ballast resistor. I use an MFJ model 4035. It has 30 =
amp supply and I've added an external 1/4 Ohm series ballast resistor to =
limit the current to 30 amps. http://www.mfjenterprises.com/Product.php?productid=3DMFJ-4035MV&nbs=
p; http://www.physics.brown.edu/physics/demopages/Demo/em/demo/5h1540=
.htm On Wed, =
Jul 28, 2010 at 3:10 PM, Keith Warren =
wrote:Hmmm. Now I need a 30A =
power supply. The best I have is 15A.-----Original =
Message-----From: tap-l-owner@lists.ncsu.edu=
[mailto:tap-l-owner@lists.ncsu.edu=
] OnBehalf Of Dale E. StilleSent: Wednesday, July 28, 2010 2:41 =
PMTo: tap-l@lists.ncsu.eduSubject:=
Re: [tap-l] 5H15.10 - Field of Wire and Iron =
FilingsKeith,If you have a hefty power supply, these =
that I have built have worked for mefor 25 years. They can =
also be used with the regular document cameras.They are 9 inches =
square and 2.5 inches tall. The plate in the boxes israise to =
the middle so that wiring could be run underneath without beingtorn =
up when storing. This also allows you to catch all the filings =
andpour them back into the shaker. One hint, the new OH =
projectors only allowyou to place that plate in the boxes at less =
than2 inches above the glass of the OH before they can't be focused =
anymore. See: http://faraday.physics.uiowa.edu/em/5h15.10.htm =
for pictures.Oh, the wire used was just solid # 12 we =
stripped the insulation off of.DaleKeith Warren =
wrote:> We need to rebuild our field of wire and iron filings =
demo, 5H15.10.> Does anybody have a version that works really =
well?>>>> -Keith>> =
NCSU>>>
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