Date: Thu Nov 2 13:40:27 2006

Author: Michael Timmins

Subject: Re: jumping rings "launcher" and load (fwd)

Post:
Do you know what type of breakers you are using? Are they thermal or magnetic
or a combination. I could be that your coil heats up before the breaker
reaches the temperature at which it "breaks".

Mike

On Thursday 02 November 2006 12:57, Dale Stille wrote:
> ---------- Forwarded message ----------
> Date: Thu, 2 Nov 2006 11:31:11 -0600 (CST)
> From: Dale Stille
> To: "John Cockman, Jr."
> Subject: Re: [tap-l] jumping rings "launcher" and load
>
>
> John and Mike,
>
> You got my curiosity going now.....so I did some real measurements on my
> coil. The demo we routinely do with this is to show this as an
> electromagnet with and without the coil. We routinely turn our variac up
> to about 80 volts for both of these demos. You can't do it for extended
> periods because the coil heats up pretty fast. So, when I measured the
> current when used without the coil it shows we are pumping 60 to 70 amps
> through this for the short time we use it. Curious, because the room
> circuit breakers are 20 amp breakers and the breaker on the variac is a 15
> amp breaker......and yet we have blown neither of these doing this demo in
> the 20 years I have been here. And before you say the breakers aren't
> working.....we know they are because we have other demos where we do break
> them on a routine basis. When we insert the coil and repeat the demo, then
> our current is down to 10 to 15 amps.
>
> According to your reports it shouldn't work......and yet it does. And it
> is also not just a single special coil that does this. I have built 4
> other coils of this design since I have been here and they all work the
> same.
>
> Later,
> Dale
> U of Iowa
>
> On Thu, 2 Nov 2006, John Cockman, Jr. wrote:
> > L = r^2*n^2/(9*r+10*l)
> >
> > r = radius of coil
> > l = length of coil
> > n = number of turns
> >
> > Inductive reactance XL = 2*pi*f*L, where f=60hz
> >
> > Impedence Z = (XL^2 + R^2)^1/2 where R is the resistance
> >
> > You probably want V/Z to be less than an amp.
> >
> > John
> >
> > ----- Original Message -----
> > From: Krishna Chowdary
> > To: tap-l@lists.ncsu.edu
> > Sent: Thursday, November 02, 2006 10:09 AM
> > Subject: Re: [tap-l] jumping rings "launcher" and load
> >
> >
> > I knew I was forgetting something obvious. Thanks to all who reminded
> > me about the inductive reactance of the solenoid+core itself contributing
> > to the overall impedance of the circuit.
> >
> > Followup question: clearly if the inductance is too small, I _would_
> > blow a fuse or melt something. The inductance is related to the number
> > of turns on the solenoid, solenoid geometry, and any conducting core
> > filling material. If I were to do this with just a simple air core
> > solenoid, does anyone have experience with dimensions, number of turns
> > per unit length, wire gauge, etc.to get a reasonable inductive load at 60
> > Hz? Again, my goal is to plug an air core solenoid into a wall outlet
> > safely.
> >
> > Again, thanks for your input.
> >
> > --
> > regards
> > -Krishna
> >
> > Krishna Chowdary
> > Department of Physics & Astronomy
> > Bucknell University

--
Mike Timmins

University of Virginia
email: mat3q@virginia.edu
phone: (434) 924-6800
mail address:
382 McCormick Rd
Charlottesville, VA 22904

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