A new mathematical model for the electrical conditions in wire‐duct electrostatic precipitators is described. The model is based on the solution of Maxwell’s equations for the electric field components and offers several advantages over numerical solutions of Poisson’s equation. The model is used to calculate the effects of back corona on (1) the voltage‐current characteristic, (2) the current‐density distribution at the collector plate, and (3) particle collection for five simple mechanisms describing the generation of back corona. Each mechanism is capable of simulating theV‐Icurves characteristic of precipitators operating in back corona, but two in particular are identified as potential back corona mechanisms on the basis of generating hysteresis in theV‐Icurves or characteristic current density variations. These mechanisms are consistent with limited experimental data. This method of calculation is useful and can be extended to more complex mechanisms for back corona generation.