U = 1 / (2muo) x B2 x V .............. (1)
Where muo is the magnetic permittivity of the vacuum.
Common permanent magnets channel energy. If we can use them to get unlimited power like the Bearden's MEG, then the Earth's magnetic field across an air core coil can achieve the same result.
Now we can do a comparison between a permanent magnet and a coil oriented to the Earth's magnetic field to get the same energy levels.
Let's consider a powerful permanent magnet, as used in a MEG, of 5,000 gauss and dimensions of 50 mm x 20 mm x 10 mm. According to the equation (1) above, the energy stored in the permanent magnet will be:
U = 1 / (8 x pi x 10-7) x (0.5)2 x (5 x 10-2) x (2 x 10-2) x (10-2), so
U = 0.995 Joules - that is to say, roughly 1 Joule of energy.
Devices like the MEG with permanent magnets don't get too many kilowatts, the reason is because that magnetic energy is constant. If we close that magnetic field in a core or magnetic circuit and we pulse that field we get 1 7 - 49
joule of energy at any desired time rate because the permanent magnet stores that energy unlimited and so if we want a power output of 1 KW as the power P we calculate:
P = dU/dt
For P = 1 KW , we need pulse 1 joule of energy for only 1 millisecond.
In the same way, if we can get power of the same levels from Earth's magnetic field, we must calculate the volume of the air core coil. By using the same equation, we see that
(0.5)2 x (5 x 10-2) x (2 x 10-2) x (10-2) = (10-4)2 x V
V is the volume of the coil we need for get the same magnetic energy levels, and in this case, V = 250 m3
That is to say, a coil of 6.3 m diameter and 6.3 m length, placed parallel to the Earth's magnetic field, can store the same energy as that little 5,000 gauss permanent magnet which we considered for a MEG device.
But it is not necessary build a huge coil, we can use a smaller coil. The enclosed magnetic energy will be lower, but as P = dU/dt we must raise the frequency of the pulses to obtain the same power level coming from a bigger coil. For example, an air core coil of 1 meter diameter and 1 meter length according to equation (1), stores an energy of:
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