Because of the steel's magnetic properties the current flowing threw the bolt as well as the steel around it will get hot because of induction.
Who said I was working with AC current?
And just about every electrical device made has steel as some part of the current path.
For that matter I can induce a current in any conductor and produce heat. Have you ever taken apart a "mechanical" speedometer. It is really an electrical device. There are permanent magnets in there, inside a little aluminum drum. The relative motion sets up a little induced current in the aluminum drum. The induced currents create a small magnetic field in the little drum and the thing acts like a little induction motor with a ton of slip. Increases the relative motion, the induced current in the little drum increases, the field increases, the torque increases, and it overcomes the spring and the needle moves.
We have magnetically induced current in things all the time. Somebody puts an electric motor together in the field and bangs the laminations a little bit and they short together, increase in eddy-currents and heat.
Why is it you think my vice grips are an engineering no-no, what are alligator clips made out of?
And I can tell you, after 40 some years of breaking my fingers in the field, I can tell you how they fail. The guys either don't clamp them tight, or they clamp them on something dirty The resistance from the loose/dirty connection heats them up to where the jaw loses it's strength. and they loosen up more, eventually the jaw loosens up enough for an arc to form and then,,,,,,,,,,,,,
But I can tell you this, they last about a million times longer than anything you can buy off the shelf, and that is just from empirical knowledge
Here is a little thing to try, Take an old squirrel cage motor, yank the rotor out of it, make up a jig to hold a piece of conductive material of your choice in the center of the armature, energize the armature, and watch whatever you are holding in the center get hot.
Don't burn your hands
That is the kind of stuff I did as a child, my mom said I had no interest in toys. Just books and things my grandfather and his friends gave me to take apart to see how it worked.
And you know how those old boys were, they let me smash fingers, bust knuckles, get minor shocks, and burns. Thank God they did.
These are clamps for emergency power hook ups, and for welder's ground clamps. NASA is not involved
