How can I distinguish between three identically shaped bars of permanent magnet, soft iron and copper, NON-DESTRUCTIVELY and WITH MY EYES CLOSED??
One isn't attracted to anything. Now you have the CU. One is attracted to steel, while the other isn't. I hope you have more than just the three bars. Do you have a reference metal, like a desk leg which will respond to a magnet? If you have a way to check position on a nearly frictionless surface, the permanent magnet will always try to align itself with Earth's magnetic field while the other will not.
no answer i just wanted to say thanks for the answer
The copper won't stick to either other bar statically. However, if you move the magnet past the copper bar, it'll move a little (Faraday's Law effect), but moving the steel bar past the copper bar won't do anything. So, once you know the copper bar, you can use it to figure out which other bar is the magnet. Edit: You should still be able to feel the eddy-current-induced forces when moving the copper and magnet past each other. I think this is the answer they're looking for.diamagnetic effects are too small to notice (trust me, we've been trying to work out a diamagnetism lab exercise off and on for years, and it's just too subtle an effect for intro course equipment). The key here is to try each pair statically and then dynamically. The magnet and iron will always stick together. The magnet and copper will only stick together when moving past each other. The copper and iron will never stick together. Each bar gets tried twice as you combine three items two at a time. However, I brought this up to some non-physics friends and in the course of discussion we came up with a few other options. 1) Smell. Copper has a distinctive smell, which I'm told even paint can't mask. Most people can recognize this smell, as it smells somewhat like blood. So pick the two that don't stick together and smell 'em. 2) Heft. Copper and iron have different densities. This one is harder to pull off, though, since it's a small difference. Again, find the two that don't stick together and test. Mind you, this one could be foiled by having the denser bar include hollow spaces inside. 3) Heat. Copper and iron have different heat conductivities and heat capacities. Let both non-sticking bars reach room temperature, one will feel colder. 4) Sound. Flick each non-sticking bar with a fingernail. Copper rings while soft iron thuds, in general.
