2.Magnetic moment can be measured (with) by using the Helmboltz coil. Take a sintered Nd-Fe-B of 10×10×10 mm (SANMAG-N48M) for example, its magnetic moment could be 142.0  μWb×cm, and according to Ampere’s law the equivalent surface current should be 11.3 kA. To generate equal distant zone field strength, an electromagnet needs a square coil of 10×10×10mm loaded with a current of 11.3 kA. It is obvious that sintered Nd-Fe-B magnets are superior to electromagnets in application, especially in minitype devices with strong magnetic field.