Have always wondered this so maybe I can get an answer here: when a large industrial electromagnet is switched off and the electricity-produced magnetism ceases, is there a small amount of residual magnetism in the uncharged electro-magnet? If so, does it dissipate according to a established formula? If it exists, it is essentially free energy at that point, so could it be used for an alternate and lesser purpose before it dissipates thus saving the energy needed to produce it for this alternate use? I imagine the real question here is: if it exists, does it have any practical use before it dissipates? Or, if it exists, is it too small an amount to be of any alternate benefit? Thanks for all informed answers.