You are designing capacitors for various applications. For one application, you want the maximum possible stored energy. For another, you want the maximum stored charge. For a third application, you want the capacitor to withstand a large applied voltage without dielectric breakdown. You start with an air-filled parallel-plate capacitor that has C₀= 6.00 pF and a plate separation of 2.50 mm. You then consider the use of each of the dielectric materials listed in Table 24.2. In each application, the dielectric will fill the volume between the plates, and the electric field between the plates will be 50% of the dielectric strength given in the table.

(a) For each of the five materials given in the table, calculate the energy stored in the capacitor. Which dielectric allows the maximum stored energy?

(b) For each material, what is the charge Q stored on each plate of the capacitor? 

(c) For each material, what is the voltage applied across the capacitor?

(d) Is one dielectric material in the table your best choice for all three applications?

Table 24.2

Dielectric Constant and Dielectric Strength of Some Insulating Materials Dielectric Dielectric Strength, E, (V/m) Material Constant, K 2.8 3.3 3 x 107 6 x 10' 7 x 107 2 x 107 1 x 107 Polycarbonate Polyester Polypropylene Polystyrene Pyrex glass 2.2 2.6 4.7