6 Electromagnetic & Acoustic Science Demonstrations at Harvard University
I visited Harvard University over my spring break and met with Daniel Davis, who showed me 6 incredible natural science demonstrations which you can learn in-depth about on his department's website!
https://sciencedemonstrations.fas.har...
It really is an invaluable resource you all have access to. I hope you enjoyed the video!
Thanks again, Daniel!
0:00 Introduction
0:05 Eddy currents in Cu block
1:01 Eddy currents in Cu block at LN2 temp
2:22 Quasi-static levitation of a magnet
6:20 Meissner Effect and flux pinning
7:17 Rijke Tube
9:16 The Eternal Flame
10:23 Explosive Capacitor Discharge
Eddy current at LN2 Temp https://sciencedemonstrations.fas.har...
Eddy current levitation: https://sciencedemonstrations.fas.har...
Earnshaws theorem: https://sciencedemonstrations.fas.har...
Meissner Effect: https://sciencedemonstrations.fas.har...
Rijke tube: https://en.wikipedia.org/wiki/Rijke_tube
Eternal flame (Theory):
Hydrogen, which is less dense than air, leaks out of the hole at the top of the copper vessel. The flame initially burns gently like a candle because at first there isn't enough oxygen within to combust, so only the hydrogen emerging from the tip burns. As the hydrogen in the vessel is used up by the flame and the pressure in the vessel drops, air is pushed into the vessel from the bottom to equilibrate the pressure, and the ratio of air to hydrogen increases until the stoichiometric ratio is reached, at which point the gas mixture in the vessel explodes.
The tiny hole at the top acts like a closed end, while the other end of the vessel is open. Like a bottle that makes a sound when you blow across the top, the vessel has a characteristic "resonant" frequency that is inversely related to the (square root) of the density of the gas mixture within.
This is why the audible frequency drops over time: the density of the gas in the vessel is increasing and therefore decreasing the resonant frequency of the vessel. This means that your ears are technically acting as a crude air:fuel ratio sensor! Fun fact: The starting frequency of the siren was a C note at 440 Hz and an A at 260 Hz right before the explosion.
Explosive Capacitor Discharge: https://sciencedemonstrations.fas.har...
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@backmacsci