where ρ_v is the space charge density and ε_0 is the dielectric permittivity of free space. Since most ion collector application
involve aerosol concentration lower than 〖10〗^6 particles/cm3, and with low particle charge level, the space-charge effect on the electric field is neglected (ρ_v = 0). The electric potential is derived from the electric field intensity E and it is given by