Does the core size in an electromagnet affect the amount of weight lifted?

Answer 1

It can. If the core isn't large enough for the number of windings and the amount of current flowing through those windings, the field can saturate the core. If the core is saturated, driving more current through the windings to increase the field strength will fail to achieve that increased field strength. The current is "wasted" that way. Let's look at saturation first. Picture a horseshoe for our core shape. When direct current flows through the windings in an electromagnet, it sets up a magnetic field in the core. (The windings are wound around the core like fishing line on a fishing reel.) The lines of force go through the core material, and, since we are using a horseshoe magnet, the lines of force will travel all the way though the core and will "emerge" from one end of the horseshoe to "jump the gap" across the open end of the magnet to "get back into" the other pole. That way the magnetic field can have a "closed circuit" from the point of view of the magnetic lines of force. Magnets will always have lines of force emerging from one pole and taking some path to get to the other pole to go back into the core. And just like a pipe can allow only so much water to flow through it because of its size, the same can be said to be true with the core of an electromagnet. There is a limt as regards the number of magnetic lines of force that can pass through a core of a given size (material considerations aside). Only so many of the lines of force can pass through before saturation occurs and no more can be included. That's a function of the size of the core (as well as a couple of other factors). A bigger core will allow us to increase the lifting capacity when we increase the current in the windings. That way we can avoid saturating the core. Let's pretend we have an electromagnet that will lift, say, a ton, and it uses, say 100 amps of DC current to do that. We want to lift a ton and a half, so we try to drive 150 amps through the windings. But let's say that the core saturates at 110 amps. That means that the core won't support more magnetic lines of force than will be flowing when the current is at 110 amps. We can continue to drive more current through the windings in the electromagnet, but the lifting power won't continue to increase. The saturated core has limited the amount of weight we can get the electromagnet to lift. The core is too small to work at the elevated current we want it to work at. Electromagnets are usually designed with a specific load limit in mind. It is possible to "overdrive" the electromagnet a bit to increase load capacity, but there will be a limit to what can be done to make the magnet pick up a heavier load. The size of the core is one of the factors that will limit the capacity of the electromagnet.