TOUR OF BUDWEISER PLANT IN JACKSONVILLE, FL
SAT 03/01/2008
DEPART: 8AM
RETURN: SAT AFTERNOON/EVENING.
===============================
IF YOU HAVE SIGNED-UP TO GO (OR IF YOU DIDN'T SIGN UP, BUT YOU NOW WANT TO GO) ON THE JACKSONVILLE FIELD TRIP (BUDWEISER PLANT), PLEASE CONTACT DOUG JONES AT ONCE. I MUST GET THE NAMES SUBMITTED BY YESTERDAY AT 4:30 PM.... BUT NOBODY RESPONDED TO MY EMAIL.
EMAIL ME AT
jonesd@tcc.fl.edu
OR CALL ME AT 850-201-8120.
WE'LL LEAVE AT 8AM (REVISED TIME) FROM THE FACULTY PARKING LOT BEHIND (TO THE IMMEDIATE NORTH OF) THE SCIENCE & MATH BUILDING.
WE'LL TRAVEL IN THE TCC FORD 350 13-PERSON VAN.
AND WE'LL RETURN THE SAME DAY (SAT).
PLEASE, PLEASE, PLEASE CONTACT ME ASAP
Friday, February 29, 2008
Tuesday, February 26, 2008
Friday (2/29) meeting and tour
There will be an Engineering Club meeting on Friday, 29 February. The meeting will be short so we can go on a tour of the the parking ramp under construction on our campus.
The meeting will be in SM260 as usual. We will leave for the tour about 3:30.
The meeting will be in SM260 as usual. We will leave for the tour about 3:30.
Sunday, February 24, 2008
Compressing a Quarter
After compared to Before ...
A standard quarter is electromagnetically compressed to the size of a dime in, literally, the blink of an eye, a flash of light, and a loud crack.
The forces on the coin are produced by an estimated 100 kA current in a 10-turn copper solenoid winding. The induced current (about 1 MA) in the outer edge of the copper core of the quarter interacts with an estimated 58 T magnetic field produced by the solenoid, compressing the quarter radially. The peak field last for about a millionth of a second because the coil is vaporized by that current.
The energy needed (about 4600 J) is delivered by a 178 uF capacitor charged to 7200 V. The capacitor, which contains about 1.28 coulombs of charge, takes several minutes to reach its final voltage. A display next to the demonstration included a page on the principles of operation of a quarter shrinker from "Stoneridge Engineering", the Teslamania web site of Bert Hickman that gave additional details for a system similar to the one we saw. My independent calculations at the bottom of this article roughly confirm what is on that page and the display at the magnet lab.
Side comment. You would get 4600 J of energy if you dropped 47 kg (about 100 pounds) a distance of 10 m (about 33 feet). Now imagine all of that energy concentrated int the small area of a quarter. Splat.
Tools of the trade:
An assembled coil is in the background. The coil itself (left foreground) is about 10 turns of 14 gauge wire (wire that would normally carry no more than 15 A in commercial use, and will melt if used with 166 A). The quarter is sandwiched between two cylinders of G10 fiberglass (right background) to center it within the coil. (Wood had been used in the past, but the G10 survives and can be reused from year to year.) Tape holds it all in place.
Centering the quarter and ensuring it is perpendicular to the magnetic field is crucial to making sure the forces compress the coin rather than twist it. Oh, yes, and the vial contains fragments of copper coils used in past experiments. The lighter colored pieces are probably stainless steel chipped off of the box that is used to contain the explosion of the coil.
This last photo shows the interior of the box used to contain the explosion of the magnet coil. You can see the copper from the used coils embedded in it. I also notice that the stainless steel panels on those three sides appear to have been added after the fact to the inside of Lexan panels that appear to have been the original design plan.
The Physics Details:
I collected a lot more details this year than I managed to get last year, correcting some of the information I used for back-of-the-envelope example in PHY2049 this year and last. [I had remembered the 1 MA current, but not that it was the induced current in the coin or the number of turns, and did not have enough info to estimate the R or L of the circuit being used here.] I now know he used 14 AWG 200C copper magnet wire with 10 turns in the coil. That info, and my estimate that the coil has an inner diameter of 2.4 cm (to fit around a quarter) and a length of between 1.7 cm (absolute minimum for the wire diameter) and 2 cm, are essential to a qualitative understanding of what is going on.
The length of the coil plus 10 cm for each lead is about 1 m, so we can estimate its resistance at about 0.008 ohm. All other conductors are large bus bars and will contribute little to the resistance of the circuit.
The coil that produces the magnetic field is too short to be correctly modeled as a solenoid. If we do that anyway, however, we require about 92 kA to produce 58 T, while 65 kA (see below) produces 41 T. These numbers assume 10 turns and a 2 cm length. Only 78 kA is needed to make 58 T (or 48 T from 65 kA) if the solenoid is 1.7 cm long. We always want the coil as tightly wound as possible!
We also get an inductance L = 2 uH for a 2 cm coil. An on-line calculator (of unknown reliability) says those dimensions would give 1.8 uH, while 1.7 cm gives 2.0 uH. I will use L = 2 uH as a conservative value. Notice that a shorter length makes the inductance bigger, which is a bad thing.
The RC time constant of 1.4 us (micro seconds), with an initial current of 900 kA, tells us what would happen if there was no coil (inductance) in the circuit. Unfortunately, the coil does not like a rapidly rising current. It would take 250 us (0.25 ms) for the current to reach 570 kA if we had just the coil with an ideal 7200 V battery. However, this is actually an un-driven LCR circuit, with all three elements playing a role. The circuit has an inductive time constant of 500 us and a natural frequency of about 53,000 rad/s. The solution to this problem says a peak current of 65 kA will be reached after 19 us. A smaller inductance makes the current bigger, by the way. The estimated inductance is a critical quantity. Reducing the inductance to 1.8 uH will increase the current to 78 kA. Notice that this is just what we need to produce 58 T in a 1.7 cm coil.
Faraday's Law says the large dB/dt produces a large EMF around the edge of the coin, which acts like a single turn in a 10:1 transformer. This leads to a rough estimate of an induced current of 650 kA (perhaps 780 or 920 kA) around the edge of the coin.
Even with "only" I = 65 kA and B = 41 T, the compressive force due to the 650 kA current induced in the outer edge of the coin would be something like 2 MN. If we really have I = 78 kA and B = 58 T, the force increases to 3.4 MN.
This force only acts for a micro second or so at the peak of the sine function that describes the current (before the coil is torn apart by the equal and opposite repulsive force of the field on the coil). The total impulse is not very large, although the total energy is significant even if a lot of it is wasted.
A standard quarter is electromagnetically compressed to the size of a dime in, literally, the blink of an eye, a flash of light, and a loud crack.
The forces on the coin are produced by an estimated 100 kA current in a 10-turn copper solenoid winding. The induced current (about 1 MA) in the outer edge of the copper core of the quarter interacts with an estimated 58 T magnetic field produced by the solenoid, compressing the quarter radially. The peak field last for about a millionth of a second because the coil is vaporized by that current.
The energy needed (about 4600 J) is delivered by a 178 uF capacitor charged to 7200 V. The capacitor, which contains about 1.28 coulombs of charge, takes several minutes to reach its final voltage. A display next to the demonstration included a page on the principles of operation of a quarter shrinker from "Stoneridge Engineering", the Teslamania web site of Bert Hickman that gave additional details for a system similar to the one we saw. My independent calculations at the bottom of this article roughly confirm what is on that page and the display at the magnet lab.
Side comment. You would get 4600 J of energy if you dropped 47 kg (about 100 pounds) a distance of 10 m (about 33 feet). Now imagine all of that energy concentrated int the small area of a quarter. Splat.
Tools of the trade:
An assembled coil is in the background. The coil itself (left foreground) is about 10 turns of 14 gauge wire (wire that would normally carry no more than 15 A in commercial use, and will melt if used with 166 A). The quarter is sandwiched between two cylinders of G10 fiberglass (right background) to center it within the coil. (Wood had been used in the past, but the G10 survives and can be reused from year to year.) Tape holds it all in place.
Centering the quarter and ensuring it is perpendicular to the magnetic field is crucial to making sure the forces compress the coin rather than twist it. Oh, yes, and the vial contains fragments of copper coils used in past experiments. The lighter colored pieces are probably stainless steel chipped off of the box that is used to contain the explosion of the coil.
This last photo shows the interior of the box used to contain the explosion of the magnet coil. You can see the copper from the used coils embedded in it. I also notice that the stainless steel panels on those three sides appear to have been added after the fact to the inside of Lexan panels that appear to have been the original design plan.
The Physics Details:
I collected a lot more details this year than I managed to get last year, correcting some of the information I used for back-of-the-envelope example in PHY2049 this year and last. [I had remembered the 1 MA current, but not that it was the induced current in the coin or the number of turns, and did not have enough info to estimate the R or L of the circuit being used here.] I now know he used 14 AWG 200C copper magnet wire with 10 turns in the coil. That info, and my estimate that the coil has an inner diameter of 2.4 cm (to fit around a quarter) and a length of between 1.7 cm (absolute minimum for the wire diameter) and 2 cm, are essential to a qualitative understanding of what is going on.
The length of the coil plus 10 cm for each lead is about 1 m, so we can estimate its resistance at about 0.008 ohm. All other conductors are large bus bars and will contribute little to the resistance of the circuit.
The coil that produces the magnetic field is too short to be correctly modeled as a solenoid. If we do that anyway, however, we require about 92 kA to produce 58 T, while 65 kA (see below) produces 41 T. These numbers assume 10 turns and a 2 cm length. Only 78 kA is needed to make 58 T (or 48 T from 65 kA) if the solenoid is 1.7 cm long. We always want the coil as tightly wound as possible!
We also get an inductance L = 2 uH for a 2 cm coil. An on-line calculator (of unknown reliability) says those dimensions would give 1.8 uH, while 1.7 cm gives 2.0 uH. I will use L = 2 uH as a conservative value. Notice that a shorter length makes the inductance bigger, which is a bad thing.
The RC time constant of 1.4 us (micro seconds), with an initial current of 900 kA, tells us what would happen if there was no coil (inductance) in the circuit. Unfortunately, the coil does not like a rapidly rising current. It would take 250 us (0.25 ms) for the current to reach 570 kA if we had just the coil with an ideal 7200 V battery. However, this is actually an un-driven LCR circuit, with all three elements playing a role. The circuit has an inductive time constant of 500 us and a natural frequency of about 53,000 rad/s. The solution to this problem says a peak current of 65 kA will be reached after 19 us. A smaller inductance makes the current bigger, by the way. The estimated inductance is a critical quantity. Reducing the inductance to 1.8 uH will increase the current to 78 kA. Notice that this is just what we need to produce 58 T in a 1.7 cm coil.
Faraday's Law says the large dB/dt produces a large EMF around the edge of the coin, which acts like a single turn in a 10:1 transformer. This leads to a rough estimate of an induced current of 650 kA (perhaps 780 or 920 kA) around the edge of the coin.
Even with "only" I = 65 kA and B = 41 T, the compressive force due to the 650 kA current induced in the outer edge of the coin would be something like 2 MN. If we really have I = 78 kA and B = 58 T, the force increases to 3.4 MN.
This force only acts for a micro second or so at the peak of the sine function that describes the current (before the coil is torn apart by the equal and opposite repulsive force of the field on the coil). The total impulse is not very large, although the total energy is significant even if a lot of it is wasted.
Tesla at the Magnet Lab
"Conducting" Electricity
The large Tesla coil shown here was producing about 250 kV at 200 kHz. The presence of an aluminum rod nearby alters the spark pattern because the current being carried off by the sparks is drawn to the grounded conductor rather than something like the overhead lights up by the ceiling.
The sparks look purple because of the emission lines from nitrogen gas. (The spark results when air molecules, mostly nitrogen, get ripped apart by the high voltage. The current is carried by a plasma.) A bare hand works almost as well as an aluminum rod, since your body is a conductor.
At high frequencies (such as 200,000 Hz), the current flows over the surface of the body. The only risk is from a burn at the point of contact. Based on the reaction of one other demonstrator, you can definitely feel it. This photo was really spectacular. The yellow spots you see are where it is burning his hand.
Important Note:
Frequency is the difference between life and death. A low frequency (such as 50 or 60 Hz) Alternating Current would be fatal at those voltages. That would go through your body and, partly because it is so well matched to the frequency our nervous system operates at, would stop the heart. In contrast, we easily get 200 kV from a van de Graaff generator in lecture demos, but the resulting small Direct Current only produces a painful shock.
Musical Reindeer
The sparks emanating from a small stuffed reindeer sitting on a smaller Tesla coil produced music. (Click the photo for a much bigger version.)
What was happening was that the air gets heated by the glowing discharge you see in the photo. If the intensity of the sparks varies at 5000 times per second (too fast to see or photograph), you get a sound wave of 5000 Hz produced in the air instead of the crackling sound of the sparks. They modulating the amplitude of the voltage delivered to the coil (and putting wires in the stuffed animal to produce many sharp points for spark production) with a music source, and you hear music.
The music went away, or was altered, if a rod was used to draw off the current in a single spark rather than the discharge you see here. Very nice.
The large Tesla coil shown here was producing about 250 kV at 200 kHz. The presence of an aluminum rod nearby alters the spark pattern because the current being carried off by the sparks is drawn to the grounded conductor rather than something like the overhead lights up by the ceiling.
The sparks look purple because of the emission lines from nitrogen gas. (The spark results when air molecules, mostly nitrogen, get ripped apart by the high voltage. The current is carried by a plasma.) A bare hand works almost as well as an aluminum rod, since your body is a conductor.
At high frequencies (such as 200,000 Hz), the current flows over the surface of the body. The only risk is from a burn at the point of contact. Based on the reaction of one other demonstrator, you can definitely feel it. This photo was really spectacular. The yellow spots you see are where it is burning his hand.
Important Note:
Frequency is the difference between life and death. A low frequency (such as 50 or 60 Hz) Alternating Current would be fatal at those voltages. That would go through your body and, partly because it is so well matched to the frequency our nervous system operates at, would stop the heart. In contrast, we easily get 200 kV from a van de Graaff generator in lecture demos, but the resulting small Direct Current only produces a painful shock.
Musical Reindeer
The sparks emanating from a small stuffed reindeer sitting on a smaller Tesla coil produced music. (Click the photo for a much bigger version.)
What was happening was that the air gets heated by the glowing discharge you see in the photo. If the intensity of the sparks varies at 5000 times per second (too fast to see or photograph), you get a sound wave of 5000 Hz produced in the air instead of the crackling sound of the sparks. They modulating the amplitude of the voltage delivered to the coil (and putting wires in the stuffed animal to produce many sharp points for spark production) with a music source, and you hear music.
The music went away, or was altered, if a rod was used to draw off the current in a single spark rather than the discharge you see here. Very nice.
Tuesday, February 19, 2008
Lecture Schedule for Mag Lab Open House
I got an e-mail today with the details for the special lectures that will be given in conjunction with the open house at the Magnet Lab on Saturday. Click the picture to see a bigger version.
The open house runs from 10 AM to 3 PM on Saturday, February 23. These are the only events that have a specific schedule. Everything else is self-guided with small presentations taking place every 15 to 30 minutes at various locations along the tour.
The open house runs from 10 AM to 3 PM on Saturday, February 23. These are the only events that have a specific schedule. Everything else is self-guided with small presentations taking place every 15 to 30 minutes at various locations along the tour.
Schedule for Wednesday Town Hall Meeting
Click on the image below to see the schedule for Wednesday evening's Town Hall meeting at The Brogan Museum. The program runs from 7:00 to 8:30 with (free) registration from 6:00 to 7:00 and a reception in the museum from 8:30 to 9:30. (The lunar eclipse is total from about 10:00 to 10:50, so there is plenty of time to leave the program and watch the eclipse. Telescopes will be set up at the gazebo on Lake Ella, in the science quad at TCC, and next to the Keen building at FSU if you want a close up view.)
"The Brogan" is located on Kleman Plaza downtown, behind City Hall and just NW of the Capitol. Parking is availble (for a fee) in the Kleman Plaza parking ramp as well as (for free) at meters along some nearby side streets.
"The Brogan" is located on Kleman Plaza downtown, behind City Hall and just NW of the Capitol. Parking is availble (for a fee) in the Kleman Plaza parking ramp as well as (for free) at meters along some nearby side streets.
Monday, February 18, 2008
Ion Sancho to lead voter education forum at TCC
[[ Although this is NOT Engineering information per se, the topic is of great interest to all citizens of a representative democracy; therefore, I post it. DJ. ]]
As part of its Black History Month celebration, Tallahassee Community College will host a voter education forum from noon to 1 p.m. on Tuesday, February 19 in the College’s Student Union Ballroom.
With Floridians now looking ahead to November’s general election, the College will offer students, faculty and staff the opportunity to learn about the importance of voting as well as voter’s rights.
Ion Sancho, Leon County Supervisor of Elections, will serve as the forum’s keynote speaker. Sancho is a highly sought-after speaker in the area of voter’s rights and voting protocol. On Tuesday, he’ll educate attendees on the importance of voting and how it relates to what is sure to be an historic 2008 presidential election.
Tom Dinh, TCC’s Student Government Association President, and representatives from TCC’s College Democrats and College Republicans are also slated for Tuesday’s agenda. A brief question and answer session is also scheduled, time permitting.
TCC will offer additional opportunities during the remainder of the month of February to celebrate the accomplishments of African-Americans who have made significant contributions worldwide.
For more information on Black History Month events at TCC, contact Cherry Alexander at (850) 201-8396 or email alexandc@tcc.fl.edu.
Subscribe to:
Posts (Atom)
