2 metals: one an electro magnet, the other a metal plate; when joined by welding, does it retain its magnetic power?
Assumming the plate is ferrous, similar in permeability to the core of the electromagnet, it will redistribute the lines of flux a bit, which instead of leaving the end poles of the core, will follow the plate out some distance then go through air to get to the other pole . This may be desireable or not, depending on your application, in particular where you want the lines of flux to flow though. Think of flux flow as similar to current flow, where ferrous and other magnetic materials are a very low resistance, and air and all other materials as a very high resistance. Your plate, if ferrous, provides a small amount of parallel low-resistance pathway for the flux, increasing the total flux for a given magnetic force. Flux density at the opposite end, the end not welded to a plate, will increase slightly. If the plate is non-ferrous, brass, whatever, the magnetic field will not be affected, since such materials have the same low permeabilty (high resistance to flux flow) as air. You don't mention your goal. If it's simply for mounting purposes, I'd say use a non-ferrous plate to avoid altering the the magnetic properties.
I only use the remote panic device to scare little children
Force is proportional to flux density. Flux density will be reduced if area is increased. Hence the decrease in force.
HelloI read Gary H's answer and agree but wanted to add just a tad to it.The electromagnets capacity is a ratio of iron core to copper windings a flux field can be easily seen in the iron filing experiment and there are mathematical ways of determining the lifting strength of these. However if you connect the iron core by welding to another plate like a base plate of steel you can only be sure of the magnets capacity on the side opposite the base. Assuming that there is no redistribution of flux density the distance and magnitude of lines cut are decreased and therefore reduce considerably the effect of the magnet(on the plate side) The fact that the copper windings are in close proximity to the base might induce a small current in the plate and actually lower the output of your device. Before welding this thing up you might want to experiment with positional layouts. As an example the magnet has two distinct ends and since it is toroid has an outer side(s).In building the magnet , if that is the plan, you might let the core extend beyond the windings(reducing induction) on one end this would aid in the attachment process and would not affect the capacity as it is out of the flux field (relatively).From the E.
Who do you think invented the remote panic alarm? *big grin*
