![]() If it's not pointing north (aligning itself with the earth's magnetic field), the needle will feel a torque trying to rotate it towards north. What's a more practical, real world example? Consider a compass needle. The magnetic dipole moment is how much torque will try rotating the magnet to align with the MRI's field. Imagine placing a magnet inside a space that has a strong magnetic field, like the inside of an MRI machine. For example, if you turn a bolt with 2 ft long wrench, applying 10 lb of force on the end of the wrench, you would be turning the bolt with 10 x 2 = 20 ft lb of torque If you're metrically inclined, you might describe a 44.5 Newton force on a 0.61 meter wrench, yielding a 27.1 N m torque.īy definition, the magnetic dipole moment is the turning moment (the torque that's trying to rotate the magnet) that a magnet "feels" in a given magnetic field. Moment is an engineering term used to describe a torque value. We're often asked what the dipole moment of a given magnet is? What does this mean? What is the dipole moment? There's a lot more to learn than we'll go into here in a simple unit converter! If you dive into the physics and math of these properties, you'll find a lot more interesting, complex stuff going on. Since B = µH, it's a fair assumption if the material is air. There are times when saying that 1 oersted is like 1 gauss works out well. In some ways, you might argue that these things are really the same. The second half of our Magnet Grades article has a great step-by-step description about how these curves are measured. You can find BH curves for various magnet grades on our BH curves page. One axis of this curve is B (flux density expressed in gauss, comes from the magnet itself) and the other axis is H (the applied or external magnetic field in the magnetizing fixture, expressed in Oe). It describes how much field strength is required to magnetize a magnet, and more importantly for magnet users, how the magnet will perform. The demagnetization curve of a magnet material describes it magnetic properties. Historically and commonly, this field strength is expressed in A/m or Oe. The magnet is exposed to a magnetic field strong enough to magnetize the magnet. For a brief instant, a strong magnetic field is created by running a lot of electric current through the coil of wire. In practice, this means the magnet material is placed in a fixture, sitting inside a big coil of wire. When manufacturing permanent magnets, magnet material is magnetized by exposing it to an external magnetic field. Stick a magnetometer on the surface of this magnet and we'll measure magnetic flux (often called field strength). For example, a D82 disc magnet has a surface field of about 2,952 gauss. When we think about the "field strength" at the surface of a magnet (the Surface Field), we're looking for something expressed in gauss. How is this different than the flux density expressed in gauss or tesla? Why are there 2 different units? Are they the same thing? It is commonly expressed in amperes/meter (A/m) or oersted (Oe). There's another, somehow different unit for field strength. The magnetic field diagrams here at use color to indicate the strength of the flux density.The average flux density here on the surface of the earth is about 0.5 gauss, though it varies from 0.22 to 0.6 gauss. ![]()
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