We'll start with quarter shrinking at first, because the physics apply to the other experiments as well. For starters, I will mention that wiring up a circuit and shrinking a quarter is quite easy, but the process behind it is much more complex than it first appears. To shrink a quarter, a coil must be constructed that is *just* larger in diameter than a quarter, and has around 10 turns or so of relatively light gauge wire (I've seen #18 work well). The quarter is then placed inside the coil, and a high-voltage capacitor is charged up using rectified AC from a transformer (diode placed in series with transformer output - watch the polarity). As soon as the capacitor is charged to the required voltage, it is then shorted into the small coil wrapped around the quarter. If a hand-operated switch is used to discharge the capacitor, the switch will be severely damaged, and the person operating it will most likely be injured. Use a spark gap or trigatron to do it. (A trigatron is basically a triggered spark gap...put HV on it and it fires). Now is a good time to list the numerous safety hazards posed by this experiment.
Shrapnel containment: The experiment should be be conducted inside a suitable metal or plastic enclosure to contain flying shrapnel. Polycarbonate (Lexan) is usually the preferred material because of its high strength and resistance to shattering.
Proper Ventilation: The high peak currents in the coil will cause it to flash into a cloud of smoke. Any insulation on the wire will burn or explode, releasing several highly toxic gasses into the air. Make sure there is proper ventilation to get rid of the fumes.
Hearing Protection: The resulting explosion from this experiment heats the air to extremely high temperature in a very small timeframe, resulting in the formation of a strong air pressure wave to be emitted. Distance yourself from the equipment, and wear earplugs.
Strong EMP Production: A strong magnetic field will radiate from the coil and wiring when the spark gap is shorted across. This field will induce a voltage in the wires of any electronic equipment in the vicinity, turning it useless after the experiment is performed. The field will travel through the walls, flooring, and cielings in your house or apartment, so beware. You don't want to pay for your neighbors stereo or television.
Lethal stored energy in capacitor: Capacitors are sometimes referred to as "energy storage devices". In this experiment, the coil and/or wiring may explode before the capacitor has time to release all of its energy, meaning that there will still be a significant voltage stored in the capacitor after the experiment has been performed. The capacitor *must* be discharged prior to working with it.
When the spark gap is shorted across, this completes the circuit and current will begin to flow through the coil. Now: Say for instance you took a capacitor the size of a car, and charged it to 12V. Now you short this capacitor into the quarter-shrinking coil, and it just turns into a lightbulb. But say you take a much smaller capacitor - say the size of a gallon of milk, and charge it to 15000 volts. And when you short it into the coil - you notice that it explodes, turning it into nothing more than a large puff of smoke. This is the current risetime that is doing the trick. Current rise-time is defined as being the time it takes for the current to change from one value to another (ex. 0A to 10,000A in one second). Higher voltages result in faster (denoting time) current risetimes. A lower voltage capacitor will drag out a small amount of current over a long period of time, but a high voltage capacitor will discharge the same amount of current in microseconds, resulting in the production of a super high peak current.
The purpose of the coil is to induce a current into the quarter. The coil and the quarter together act as a transformer - where the coil is the primary winding and the quarter is the (shorted) secondary winding. We know that the input and output currents in a transformer are related to the turns ratio:
First situation: Few primary turns and lots of secondary turns = a large primary current and a small secondary current.
Second situation: Lots of primary turns and only a few secondary turns = a small primary current and a large secondary current.
It's the second situation that we're looking at with quarter shrinking. If you put a massive amount of current into the primary (the coil), then you'll get a reallymassive current in the secondary (the quarter). We know that whenever there is current flowing through a conductor, a magnetic field will be present, and this field and current are both proportional to each other. So: wherever there is powerful current, there's a powerful magnetic field.
And vice versa! Whenever a powerful magnetic field is produced, there will be a powerful current flow induced into any nearby conductors. (the basics of transformer operation)
This is exactly how a quarter is "shrunk". The field around the coil opposes the field around the quarter, causing the two objects to physically "fight" against each other. (Just exactly like a north pole on a magnet will repel or fight a north pole on another magnet held close.) Of course, the coil is torn apart because of its weak physical construction, and the shape and size of the quarter is severely distorted. And given enough power, the quarter will be blown apart, also.
The powerful magnetic fields surrounding both the coil and quarter oppose each other, causing the quarter to physically fold into itself and the coil to be forced out away from the quarter (blown apart). The end result is a quarter that is a degree smaller than its original size. How much smaller depends on how strong the two fields were = how fast the current rise-time was = the V and C rating of the capacitor that was dumped into the coil. Basically, it all boils down to the electronics term called Work. Work is measured in Joules, and some capacitors have this as a faceplate rating.
Of course - the more work a capacitor can do (the larger the capacitor) the better! Also, the capacitor's voltage rating is very important also, because of the current rise-time factor mentioned earlier.
Keeping in mind that the coil will induce a current into *any* nearby conductor:
1. Wind a 10 turn coil around a soft drink can. The can will implode as it is forced away from the coil. With a large enough capacitor bank, the can will be crushed so rapidly as to cause the air inside to rip the can apart. With smaller capacitors, the can is only "crimped" in where the coil turns touch the side.
2. Construct a copper ring out of 3/8" copper tubing, and place it onto a tightly wound 12 - 15 turn coil made of 14 gauge wire. Make the ring diameter the same as the coil's diameter, so you can get a maximum coupling coefficient between the two inductors. The coil and copper ring will violently repel each other, resulting in two physical forces. 1.) The coil is smashed away from the ring into the ground, and 2.) The ring is shot upward into the air. Personally, I have achieved heights greater than 150 feet with only a 2kJ capacitor bank, charged to 5,000 volts.
Please email us if you have any questions or comments. Remember to be careful - big capacitors are truly dangerous. Start small and learn the basics first. Go to Walmart and ask for a few used disposable cameras...crack them open and play with the electrolytics inside. They're relatively low voltage (300V), a good size. Everyone I know started off with photoflash caps.
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