Materials like iron are composed of tiny magnetic domains, which each behave like tiny magnets. The domains themselves are composed of even tinier atoms, which are themselves microscopic magnets, lined up within the domain. Normally the domains cancel each other out. But in magnets, like a compass needle, more of the domains are lined up in the same direction, and so the material has an overall magnetic field.
Earth’s core is mainly iron and nickel, so could its magnetic field be caused the same way as a compass needle’s? No—above a temperature called the Curie point, the magnetic domains are disrupted. The earth’s core at its coolest region is about 3400–4700°C (6100–8500°F), much hotter than the Curie points of all known substances.
But in 1820, the Danish physicist H.C. Ørsted discovered that an electric current produces a magnetic field. Without this, there could be no electric motors. So could an electric current be responsible for the earth’s magnetic field? Electric motors have a power source, but electric currents normally decay almost instantly once the power source is switched off (except in superconductors). So how could there be an electric current inside the earth, without a source?
The great physicist Michael Faraday (a creationist) answered this question in 1831 with his discovery that a changing magnetic field induces an electric voltage, the basis of electrical generators.
Imagine the earth soon after creation with a large electrical current in its core. This would produce a strong magnetic field. Without a power source, this current would decay. Thus the magnetic field would decay too. As decay is change, it would induce a current, lower but in the same direction as the original one.
So we have a decaying current producing a decaying field which generates a decaying current … If the circuit dimensions are large enough, the current would take a while to die out. The decay rate can be accurately calculated, and is always exponential. The electrical energy doesn’t disappear—it is turned into heat, a process discovered by the physicist James Joule (a creationists) in 1840.
This is the basis of Dr Barnes’ model.