I can find equations to give the force of an electromagnet on a piece of iron when the iron touches the electromagnet. But what about when the iron is some distance from the electromagnet? ...
Imagine we have an induction coil which is strong enough to heat a sheet of metal. We can put a sheet of ferromagnetic metal close to the coil at distance $h_1$, and it gets heated to temperature ...
If you had a powerful electromagnet in the shape of a hollow sphere in which the top and bottom halves are the opposing poles, what can the magnetic filed at the center of the sphere be used for?
I invented a flying engine moving entirely by magnetic forces (such as the force related with magnetic field of the Earth). See http://porton.wordpress.com/2011/12/23/magnetic-vehicle/ The question ...
Do multiple permanent magnets aggregated together approach the same strength as a single magnet of the same size?
Here's an applied physics question. ;) If I buy some cube or sphere magnets like these, can I aggregate them together to create a stronger magnet (almost as strong as a single magnet)?