witricity -- I'd like some opinions Witricity is the name of a company that hopes to sell wireless power transfer. I question their basic physics, and I'd appreciate any comments. I have no commercial interest in any of this -- it's purely an academic exercise. Also, I'm not trying to rip this company -- I'm just using the name for a reference. I would be glad to be proven wrong. One of the main folks at this company is from MIT, and I've seen some of his papers -- more math than I'm comfortable with, but I still disagree. (perhaps foolishly). The concept that they espouse is resonant coils. The transmitting and receiving coils are resonant, and they are claiming that this boosts the efficiency of the transfer. One of the examples that they sometimes use is the shattering of glass via a specific sound frequency. I disagree based on the following: 1. The receiver resonance is degraded when power transfer becomes significant. The 'Q' of a resonant circuit is related to the resistance in that circuit. In this case, it would seem to be a parallell LC circuit with the power drawn being represented by a low value resistance -- also in parallel. For any serious power transfer, I believe that the parallel resistance would essentially degrade the resonant effect, until it was negligible. 2. The glass shattering example would not seen to be applicable. This is a short term event, and does not really represent continuous power transfer. If I understand it correctly, sonic waves at the resonant frequency of a glass object will be more easily sustained. There is no power being drawn from this system, the glass is merely vibrating at its natural frequency. At some point, the vibrations cause enough physical shifting to overcome the structural bonds. There is efficient coupling of the sonic energy to the glass. However, there is no output from the glass, except for the brief amount when the glass shatters. A better example might be one showing how mechanical power could be derived by exciting a tuning fork with the appropriate sonic energy. Again, I welcome all responses.