The following symbols are used throughout this recommended practice and are defined as follows. A = ampere (coulombs per second). Electric current; the quantity of charge passing per second through a given point. C = capacitance (farads), d = diameter (meters), e = 2. 718 [base of Napierian (natural) logarithms], E = V/m = electric field strength (volts per meter), ε = dielectric constant of a material, 0 = 8. 845x10-12 farads per meter (electrical permittivity of a vacuum), ε₀ = electrical permittivity of a material (farads per meter), Is = streaming current (amperes), К = liquid conductivity (picosiemens per meter), µ = ion mobility (square meters per volt-second), µm = micrometers (microns) = 10-6 meters, -m = electrical resistivity (ohm-meter), P = pressure (millimeters of mercury), Q = quantity of electrical charge (coulombs), R = electrical resistance (ohms), ρ = volume resistivity (ohm-meters), S = electrical conductance (siemens), t = elapsed time (seconds), μ = charge relaxation time constant (seconds), v = flow velocity (meters per second), V = electrical potential difference (volts), W = energy or work done (joules)