Question

In case of a Van de Graaff generator, the breakdown field of air is:

• A. $2\times {10}^8$ V $m^{-1}$
• B. $3\times {10}^6$ V $m^{-1}$
• C. $2\times {10}^{-8}$ V $m^{-1}$
• D. $3\times {10}^4$ V $m^{-1}$

Answer 1

The correct option is B $3\times {10}^6$ V $m^{-1}$

Although air is normally an insulator but at a sufficient high voltage, it ionises and become partially conducting.

The electric field at which it occurs is called breakdown field of air and is nearly equal to $3\times {10}^{6}V/m$