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5C30.20-2 - Killer Capacitor

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​5C30.20-2 - Killer Capacitor

Title5C30.20-2 - 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.

Assembly Instructions

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.


Setup Time5
Operation Time5
Preview Time10
Operation Instructions

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.**

Demo on DimeNo
PIRA 200Yes
Export Instructions (if different)
HazardsExposed High Voltage - DC Current

Killer Capacitor Coil Construction
1.       Cut 48” of solid 10 or 12 gauge magnet wire
2.       Insulate length of wire with heat shrink tubing
3.       Spray white plastic winder form and inside of aluminum outer form ring with Teflon mold release
4.       Install Teflon tape to wide section of the white plastic winder form
5.       Apply ~2 layers of fiber glass cloth strips to the white plastic winder form
a.       Use double sticky tape or a piece of tape folded over on itself to fix the fiber glass cloth in place.  You do not want the tape visible from the outside.
6.       Lay out 3, 9” long pieces of string at 90 degrees to the winding form, across the fiber glass cloth
7.       Wind the insulated length of wire to 3.75-4.3 turns around the fiber glass tape on the winding form
8.       Using the pieces of string, tie the coils together so they are compressed tightly and make sure the strings are snug
9.       Using another piece of string, tie the string so to hold the two coil ends from unwinding
10.   Place a piece of Teflon tape on the inner rim of the aluminum ring of the casting form
11.   Place the Teflon tape bottom pad on the blue casting form base and align with the central hole
12.   Place the aluminum ring with Teflon tape around the inner ring onto the blue casting base
13.   Screw down the entire white plastic winder form with attached wound wire onto the blue casting base with the aluminum ring in place
14.   Tighten down the assembly
15.   Stuff the inside of the casting form, between the wire and aluminum ring, loosely with fiber glass cloth
a.       This acts like rebar in concrete
16.   Center the form on the wood base and clamp down the lever assemblies
17.   Mix the Epoxy – 55 grams of Resin, 60 grams of Hardener, stir vigorously for at least 2 minutes
18.   Use large syringe to apply epoxy to inside casting form
a.       Make sure it is evenly distributed throughout the casting area
19.   Allow epoxy to harden for approximately 18-24 hours
20.   Unscrew inner form central restraining bolt
21.   Tap the form from the bottom to remove the central form from the assembly
22.   Remove the outer aluminum ring with a screwdriver by prying it open from the relief slot cut in the ring
23.   Remove all Teflon tape
24.   Cut away all stray stringer from casting
25.   Check that a pop can will fit inside the coil
26.   Measure, cut off excess heat shrink , bend and form the wire leads
27.   Flatten the lead ends with hammer on anvil
28.   Remove all varnish from connector leads
29.   Install new coil to Killer Capacitor assembly
30.   Test that the new coil works
Category5 Electricity and Magnetism
Subcategory5C - Capacitance
Keywordsdischarge, energy storage in a capacitor
Construction Information
killer capacitor
aluminum ring projectile - solid ring
aluminum ring projectile - split ring
aluminum foil strips - for bridging split ring
pop can
blast shield - circular