536 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1954 



NOTATION 



a Arc radius or equivalent characteristic length of cross section 



c Local capacitance at the contacts 



e Electron charge 



la Current densit.y in the arc 



ith Thermionic emission current density 



ing Normal glow current density 



tag Abnormal glow current density 



(^^sLimit) Limiting glow current density preceding glow-arc Limit transi- 

 tion 



k Boltzman constant 



I Local inductance at the contacts 



m Alass of contact metal atom 



n Number of consecutive arcs in otic breakdown 



r Resistance of the local contact circuitry 



s Separation between the contacts 



/ Time 



ich Charging time between breakdowns 



tdei Deionization time following an arc 



tg Glow duration 



Us Velocity of contact separation 



Uch Charging velociy defined as s/tch 



Uat Velocity of the metal atoms 



V Arc voltage 



Vn Residual voltage at the contacts following a breakdown of n- 

 consecutive arcs 



z Impedance {l/cf^ 



A Constant in the thermionic equation 



Aa x\rea of arc spot 



C Circuit capacitance 



E Battery voltage 



F Field strength 



/ Current 



Ig Current in a glow discharge 



Im Minimum arcing current 



Jo Liitial closed circuit current 



L Circuit inductance 



R Circuit resistance 



T Absolute temperature 



T h Absolute boiling temperature 



