At the Earth's surface, these tempests can be detected by changes in the strength of the Earth's magnetic field.
在地球表面,可以通过改变地球磁场强度来检测这些风暴。
Choose a device with the lowest SAR possible (SAR = Specific Absorption Rate, which is a measure of the strength of the magnetic field absorbed by the body).
选择一个尽可能的的最低吸收率设备(SAR=Specific Absorption Rate,是一个人体吸收磁场强度的计量单位)。
He also realised that varying the strength of an electric field would generate a changing magnetic field, even in empty space with no moving electric charges to speak of.
他同时认识到,变化电场强度将会产生一个变化的磁场,甚至在一个没有移动电子的空间中也是如此。
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