What makes a compass needle spin?

I've been thinking about the Earth and how it's inner cores work. I'm thinking it works in similar ways that a DC or a AC motor works. That would mean that the Earth has to be hollow. You cannot have spinning motion with a solid ball of rock and metal.

Or a very strong magnetic field. There are certain spots on the globe that cause computers and radios to stop working, like the Zone of Silence in Mexico. There is one story I like, where the government was testing new missiles and they said that when it came anywhere near the Zone of Silence, the missile would be pulled into it and then hit the ground miles off course. Some people say that meteors have been pulled into it from orbit.