Question

In a van de Graaff type generator, a spherical metal shell is to be a 15 x 10⁶ V electrode. The dielectric strength of the gas surrounding the electrode is 5 x 10⁷ Vm¹. What is the minimum radius of the spherical shell required? (You will learn from this exercise why one cannot build an electrostatic generator using a very small shell which required a small charge to acquire a high potential).

Answer 1

V = 15 x 10⁶ V, 

E = 5 x 10⁷ Vm^-1

r = ?