5C30.20-2 - Killer Capacitor
By charging and shorting a capacitor, a big noise can be produced and additionally, induced currents can be produced by a strong momentary magnetic field launching an aluminum ring or ripping a pop can in half, which illustrates how much energy the capacitor can store.
The killer capacitor is a self-contained unit. Make sure that the switch is closed and the unit is off before placing any attachments on the coil or placing the hand or any body part near the coil. Be sure to clean the Killer Cap if necessary as it can get really dusty during storage. Place the aluminum rings, pop cans, and blast sheild on top for storage, or nearby on a desk for classroom use.
Ear Protectors (Ear muffs) are provided for user safety. A low voltage equal capacitor is also provided to show a comparison of energy stored and thickness of dielectric materials in each.
The Killer Capacitor is three 6.7 microFarad capacitors in parallel. The total capacitance is 20 microFarads. The maximum voltage we run it at is 10.5 KV.
Remind instructors: **DO NOT TOUCH THE KILLER CAPACITOR IF IT IS CHARGED**
A closed aluminum ring can be launched using induced currents from a 4 turn coil mounted in the front of the unit through which the discharge current flows. After plugging it in, place the aluminum ring in the holder, and set the blast sheild around it. Then, pull the white string on the side to open the switch. Flip the on/off switch to on and let the gauge charge to 4, 6, & 8 kV. The voltage factor of 2 & 3 charging voltage can be quickly used to show conversion of potential energy into kinetic energy and then relate electrical potential to the maximum height potential energy by E = 1/2CV^2, (although an exact correlation is difficult to explain due to coupling efficiency and various other losses). Then release the switch and watch the ring shoot up in the air. Observe the heights relative to each charging voltage.
The procedure for the open ring, split ring, or pop can are fairly similar to the closed ring demo describe previously. When the killer cap is not charged and safe to touch, a split ring or an open ring with aluminum foil fuse, can be set ontop of the coil and blast sheild set around it. Pull the white string to set the knife switch and then carefully switch on killer cap to begin charging. Once enough charge is stored, TURN OFF THE CHARGING CIRCUIT, then pull the string to close the knife switch which instantaneouly discharges the capacitor bank through the coil. The split ring will do nothing as no currents can flow a broken circuit. For the open ring with aluminum fuse, the fuse should vaporize and also react to the coil due to the induced currents, though not as high as the solid ring. The soda can will need the maximum voltage 10.5 kV to work and the blast shield is crucial for safety. This is also much louder than the rest, so make sure to tell your audience to cover their ears. Be sure to load the can prior to any charging of the system. The can, during disharge, should collapse in the middle and blow out both the top and bottom of the coil in opposite directions.
**A possible question to ask the students: Under closer investigation, the top and bottom of the can will look slightly different. Why is the top of the can still crushed inwards while the bottom of the can has a flaired out opening? Answer: Because during the constriction, the air inside the can heats up and expands. In the top portion of the can, there is a hole for the heated air to escape from, but in the bottom portion of the can, the only opening is the one made after the constriction, so the only place it can go is out of the part that was just constricted, causing it to flair back out.**