(a) What total (excess) charge q must the disk in Figure have for the electric field on the surface of the disk at its center to have magnitude 3.0 x 106 N/C, the E value at which air breaks down electrically, producing sparks? Take the disk radius as 2.5 cm, and use the listing for air in Table 22-1.
(b) Suppose each surface atom has an effective cross-sectional area of 0.015nm2. How many atoms are needed to make up the disk surface?
(c) The charge calculated in (a) results from some of the surface atoms having one excess electron. What fraction of these atoms must be so charged?