The dashed straight line corresponds
to eqn (4.2) with Eb D 26.6 kV/cm, a value which agrees well with
measured breakdown field intensities in atmospheric air under normal conditions
(temperature 20°C; pressure 101.3 kPa; humidity 11 g/m3) for a uniform
field D 1. The highest breakdown voltage of the gap Vb D 26.6 ð 10 D
266 kV can also be found in Chapter 5,