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一、选择题 1.当导体中有________的电流时,在它的周围就会产生电磁波,无线电通信就是利用电磁波来传输信号的. 2.振荡电流每秒钟振荡的次数叫做电磁波的_______,电流每振荡1次,电磁波向前传播的距离就等于电磁波的________. 3.电磁波在空间是向各个方向传播的,它的传播速度和________一样,在真空中的传播速度
First, the multiple-choice questions 1. When the conductor has ________ current, it will have the electromagnetic waves around it, radio communications is the use of electromagnetic waves to transmit signals. 2. Oscillation current per second, the number of oscillations called electromagnetic waves _ ______, the current once every oscillation, the electromagnetic wave forward propagation distance is equal to the electromagnetic wave ________. 3. Electromagnetic waves in space is to spread in all directions, and its propagation speed and ________, in the vacuum propagation speed