This is the high voltage vaporisation of an Easter Bunny’s aluminium wrapper. If you are sqeamish, look away now. The Easter bunny meets 50,000 A might be a suitable title.
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Here the cap bank is charged to 5.8 kV (3.5 kJ). A little steel wool on each end to sparkle up the display and away we go.
The flash and bang is huge but most of the energy is directed outwards and the damage is surprisingly small. Interestingly much of the paint is blown off the aluminium foil. The explosion photo is taken just after sunset with a 2.5 second exposure to allow me time to pull the switch and for reasonable spark length. I had to back off the f stop to 13 to reduce total light pickup.
Note that 3500 joules is barely enough to melt 100 g of chocolate or heat water for a cup of coffee. It is just one 2000 watt electrical kettle for 2 seconds after all. This power is underwhelming when delivered slowly. But deliver it in 30 us and the instantaneous power rises to 116 MW (megawatts). Think of a power station output for that time. In that time frame things happen fast and furious. Local heating doesn’t have time to escape and things vaporize, magnetic fields due to the huge currents are intense and rapidly changing. These fields can tear a drink can in two, shrink a metal coin or tear a copper coil into high velocity pieces.
Currents are limited by the characteristics of the inductance of the capacitors (small) and copper bus bars (larger) but are typically up to perhaps 50 kA for my setup. It should still be within ratings at 200 kA as I have only ever run it at 1/4 capacity.
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Photo Date: April 5, 2007