Question

Here's a cool example: Permanent magnets. If B are produced by currents, then what's up with permanent magnets? You don't have to plug them in, they just work. What's the current? One idea is that it could be the e' orbiting the nucleus. A charge moving in a circular loop is a sort of current. (You'll calculate this in Problem 30.6) Let's estimate the speed of the e' using Newton's Laws: the only force is the Coulombo attraction, and we'll use centripetal ZF= F2 = mye key mouse, so v (circular) acceleration: Now, for a hydrogen atom, risxiohm, so vž 2.3 xboms. And you found (will find?) the Current from this orbiting e is Ok, so a simple orbiting e' has a magnetic dipole moment st 2ur Mas Id- ex. rrezevr = 9.2x10**a! 2 Now, as a "toy" model, let's suppose this is how magnets work - maybe in magnetic materials there's an outer valence e' that doesn't get canceled out, or whatever (not really, the "real" prcture is more complex ...) Then a small, 63.5g iron magnet might be predicted to have a lu - Miten Nations (I picked 63.5g = I mole) > M=(9x1024_x)(6X10atom) i ogole) -5,44m2 - Now I'll get a real magnet and test this ! 25 Z3 at mote'