A thin porcelain disc of diameter 500 mm and having a smoothly rounded edge carries a semiconducting glaze. At the centers of top and bottom surfaces there are 20 mm diameter metal terminals making good electrical contact with the glaze surface. With 10 kV applied between the terminals a current of 1 mA is required to flow. If the resistivity of the glaze is 600Ω m calculate the necessary glaze thickness at the electrode edges and how the thickness must be graded to ensure a constant voltage gradient along the radii.
Estimate the steady state surface temperature above that of the air ambient assuming a rate of loss of heat of
and comment on how this might affect performance in a polluted atmosphere