Testing the TK Tar Baby

[MileHigh]

Well...

In scenario 1 the energy is 0.5 Joules but in scenario 2 the energy is 0.25 Joules.  What gives?

[hoptoad]

snip...

Then I read the humbugger work on the other forum. This, plus looking at the NERD video again, made me realize that it was the layout, not the mosfets themselves, that was likely responsible for the oscs.... so I cut random wires and soldered them onto my mosfets, and placed them on some larger heatsinks, not so much for heat transfer but for capacitance. Bingo et voila! Massive Robust Feedback caused by inductance and capacitive coupling in the leads. Sensitive to motion and exact placement.

snip...

LOL - So it may be bird droppings you're looking for after all, since you had to build a birds nest for best results!! 


Cheers

[TinselKoala]

Well...

In scenario 1 the energy is 0.5 Joules but in scenario 2 the energy is 0.25 Joules.  What gives?

How do you figure that?

Mv initial = mv final. (CofM).
Scenario 1: 1 kg moving at 1 m/s = 1 kg-meter/second. Energy  = 1/2 (mv^2) or 0.5 Joules.

Scenario 2: 1 kg mass moving at 1 m/s = 2 kg mass moving at x meters per second. (CofM) Solving for x, we have x = 0.5 m/s.
Solving for energy, we have E = 1/2 (mv^2) or 1/2 (2 x 0.5 x 0.5) = 0.25 Joules... therefore aliens.

But.... you've made a trick. The simple Energy Conservation law applies to _elastic_ collisions. The part about the two weights sticking together and moving off together in the same direction means that your collision is inelastic. Conservation of momentum still applies simply. But the CofE part now needs to take into account the energy lost to sticking together, deformation, heat and so on. The fact that energy does NOT appear to be conserved in the easy naive calculation is the indication that the collision you are looking at is inelastic, and energy is lost to the moving system. If you could account for all the losses (by enclosing the whole shebang in a perfect calorimeter, for example) you would see that energy is still conserved.

This is sort of like all the little resistances and radiations that will suck the energy out of the batt-cap-switch system. A perfect inductor is sometimes easier to understand because we have "touchy feely" experience with storage of energy in a magnetic field and its conservative return, using permanent magnets. We don't have this same fingers-on experience with the electric field energy storage that happens in capacitors, so they seem especially mysterious. It's just another kind of spring, that's all, with its own set of losses that suck energy out of the spring's motion until eventually it's all gone, lost as heat.

[MileHigh]

Awesome TK, you got it!

The moral of the story is that when you short one charged capacitor to a discharged capacitor and lose one-half of your energy it's identical to an inelastic collision between a moving mass and a stationary mass.

In both cases you produce heat and that accounts for the 'missing' energy.

MileHigh

[TinselKoala]

But how do the systems know to lose exactly half their energies to heat, and keep half in KE or capacitance?