例句與造句

1. In many problems of plasma physics, it is not useful to calculate the electric potential on the basis of the Poisson equation because the electron and ion densities are not known " a priori ", and if they were, because of quasineutrality the net charge density is the small difference of two large quantities, the electron and ion charge densities.
2. It's difficult to find net charge density in a sentence. 用net charge density造句挺難的