当金属物体接触到一个交变的电磁场时，涡流会使这个物体加热。
When metallic objects are exposed to an alternating magnetic field, eddy currents cause such objects to heat up.
当振管垂直立于磁场环境中时，在交变磁场的作用下产生磁致伸缩，即沿振管的轴向作简谐振动。
Vibration tube in the magnetic field vertically brings about magnetostriction under the effect of alternate magnetic field, that is axis resonance.
在雷电电磁场的理论计算方面，提出了两种方法，即时域中的偶极子方法和频域中的时变场方法。
About theoretic calculation for lightning electromagnetic field, two analytical methods are raised, which are dipole method in time domain and time-varying field method in frequency domain.
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