If the electron flow takes place in a vacuum, as in the case of electronic valve, the electrons will travel at considerable speed, since little resistance is offered the medium.
如果电子在真空里流动，比如电子真空管，那么电子的运行速度非常快，因为介质对电子几乎不产生什么阻力。
2
Open or close the valve stem travel relatively short, and very reliable cutting action, making this valve is suitable for medium and cutting off or regulating use.