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Nearly 125 years late, wireless recharging arrives by subbywan2008-08-22 08:58:19
  Wireless recharging is easy. by AndyA2008-08-22 09:14:33
    75%-90% isn't a bad start. (n/t) by subbywan2008-08-22 09:17:44
      At three feet. by bwkaz2008-08-22 09:35:23
        Directional "antenna" maybe by Menetlaus2008-08-22 09:46:59
          It'll still be inverse square. by bwkaz2008-08-22 09:51:53
            How's that? by Menetlaus 2008-08-22 11:54:12
Assuming you have a perfect source with no dispersion, my understanding is that the power density would never decrease as the area beam would not change (not possible, unless you accept my initial assumption). In this case the efficiency would not diminish based on distance. Density = Power/Area (both P and A remain constant)

OTOH if the same amount of power is released in all directions then the power is dispersed across the area of a sphere (A = 4 * (pi) * r^2) so as the radius increases the power density drops exponentially. Double the radius and the area quadruples, so power density drops by a factor of 4. Density = Power/[4 * pi * d^2]

So something between these two, with the property that the area doubles as the distance doubles (A = 2 * d) then the loss would be the inverse of the distance. Density = power/[2 * d]

Then again... I've been wrong before and will be wrong again.
[ Reply ]
              It's not inverse-square, or plain inverse. by bwkaz2008-08-22 12:23:56
                It is inverse square if you are far enough away by hej2008-08-22 14:25:31
                  Shouldn't the near version be a line, rather than by bwkaz2008-08-22 15:43:50
                    The near version I talked about is even closer. by hej2008-08-22 16:37:28
                      Ah, I get it. Thanks! (n/t) by bwkaz2008-08-22 16:56:12
                      Lasers by weedwacker012008-08-22 20:48:04
                        Doesn't work. by hej2008-08-24 11:27:17

 

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