Magnetic Fields From Power Lines

As we know, a magnetic field emanates from a wire carrying an electric current. The field radiates out at right angles from the direction of the current. This principle is the basis for electromagnets and electric motors.

Opposing magnetic fields will cancel each other out. Thus, a double wire carrying a direct current from a power source to a load, such as a light bulb, and back again will manifest essentially no magnetic field because the magnetic fields produce by each of the two parallel wire will be opposite and will cancel out.

For large power plants, alternating current has an advantage over direct current in that it can be easily transformed from one voltage to another by the common device known as a transformer. Alternating current, or AC, operates as a sine wave. The wave starts at zero, goes to a peak, returns to zero and then goes to a negative peak before returning to zero.

This means that alternating current must have a certain frequency. The U.S. and Canada use a system that produces 60 hertz, or cycles per second. The signal for the electrons to move travels at the speed of light along the wire, but the electrons do not actually move this fast. So, the wavelength of alternating current will be the speed of light, 300 million meters per second, divided by the frequency. This would give North American alternating current a wavelength of 5,000 km.

The thought that occurred to me is that the longer the AC circuit, the more difference there will be in the point on the sine wave in the two parallel wires at any given point on the cable. In other words, the AC waves in a parallel wire will not be exactly the same when opposite each other and so will not completely cancel out.

This must mean that the cable will manifest a magnetic field alternating at the same rate as the current. Notice that when listening to an AM radio station when driving, high-tension power lines overhead will interfere with the signal while the local electric lines do not. The high voltage is not the only reason. The high-tension lines are used for long distance power transmission, meaning that the circuit is much longer than the local circuits and the parallel magnetic fields produced by current in the cables does not completely cancel out.

The point of this is concern about how these synthetic magnetic fields affect the earth's natural magnetic field. Earth's field spans the north and south magnetic poles but high-tension lines go in all directions. This means that in some places, the synthetic magnetic fields must be reinforcing earth's field and in other places weakening it.

This affects the Van Allen Belts around earth that shield us from charged particles coming in from space. In some places, particles may be blocked that would otherwise have gotten through while in other places, particles will get through that would otherwise have not gotten through.