|MadSci Network: Physics|
Hi Jordan, You could measure the strength of an electromagnet by hanging small iron weights from the magnet. When the applied weight (force of gravity acting on the weights) exceeds the force of the magnet, the weights will fall off. Steel Flat washers of the same diameter as the coil would be inexpensive and simple to use. You can weigh several washers on a food scale and calculate the average weight of each washer. The equation for the magnetic field strength, H0, in Ampere-turns per meter for an empty (air) coil is: H0 = the applied voltage / (the number of turns of wire in the coil winding X Area within the coil winding X the permeability of air). The area is pie X D squared/4, where D is the diameter of the coil winding in meters. The permeability of air, , is 4 X pie X 10 to the - 7 henry/meter The Equation is for a direct current. An alternating current applied to the coil cannot be used for lifting magnetic objects. By substituting different numbers for the applied voltage, the number of turns of wire and the diameter of the coil, you can calculate how each parameter will effect the strength of the magnet. Electromagnets can be fun, however, keep them away from recorded tapes or they will erase the contents. Enjoy that project, Bob Novak Specialist, Process R&D Carpenter Technology
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