In a Van de Graaff type generator, a spherical metal shell is to be a \(15\times10^6~\text V\) electrode. The dielectric strength of the gas surrounding the electrode is \(5\times 10^7~\text{Vm}^{-1}.\) What is the minimum radius of the spherical shell required to avoid electrical breakdown of the gas?
1. \(0.1~\text m\)
2. \(0.3~\text m\)
3. \(0.5~\text m\)
4. \(3.0~\text m\)

 
Potential difference, V = 15 x 106 V
Dielectric strength of the surrounding gas = 5 x 107 V/m
Electric field intensity, E = Dielectric strength = 5 x 107 V/m
Minimum radius Of the spherical shell required for the purpose is given by, r=VE=15×1065×107=0.3m=30cm
Hence, the minimum radius of the spherical shell required is 30 cm.