why +ve terminal only earthed in ESP? why not -ve terminal?

Question

In ESP, +ve Terminal is earthed for collecting the dust and -ve terminal is for charging the dust particles. Why +ve terminal only earthed?If -ve terminal is earthed what happens?

Answer 1

Whatever ESP is, if the markings are obvious, then - terminal is emitting electrons and the system by earthing + is being forced negative with respect to ground. If you ground both, it won't work and if you ground - but not + then I suspect you would see nearby dust particles leaping into the air with a static charge.