The insulation property of air breaks down at E= 3x 106 volt per metre. The maximum charge that can be given to a sphere of diameter 5 metres is approximately

Electric field on the surface of sphere =14πε0×qr2Its maximum value may be 3 x 106 v/m because after this value, the insulation property of air breaks.∴3×106=9×109×q/(2⋅5)2q=3×106(2⋅5)29×109=2×10−3C