1.频率的概念就是从机械旋转运动来的,ω=ddθt定义为角速度,对于周期运动,角速度也就是角频率。通常θ以反时针为正,因此转动的正频率是反时针旋转角速度,负频率就是顺时针旋转角速度。这就是它的物理意义,正、负号不影响它的物理意义。2.电的单位向量(电压或电流)围绕原点的? 1. The concept of frequency is from the mechanical rotation of the movement, ω = dd θt is defined as the angular velocity, for periodic motion, the angular velocity is the angular frequency. Normally, the counterclockwise θ is positive, so the positive rotation frequency is the anti-clockwise rotation angular velocity and the negative frequency is the clockwise rotation angular velocity. This is its physical meaning, positive and negative sign does not affect its physical meaning. 2. Electricity unit vector (voltage or current) around the origin?