The gas in the precipitator behaves in a highly non-Ohmic manner--indeed, the current is proportional to the third power of the electric field! This means that the effective resistance of the gas depends strongly on the applied field. After a layer of dust has accumulated on the ground plate, the effective resistance of the gas is . Once a layer of dust has accumulated, the effective resistance rises to . What is the magnitude of the electric field between the plates when there is a layer of dust