﻿Pressure 
  Effect 
  in 
  Corona 
  Discharge. 
  

  

  267 
  

  

  In 
  positive 
  discharge 
  the 
  value 
  of 
  the 
  ratio 
  is 
  consistently 
  

   higher 
  than 
  that 
  in 
  negative. 
  This 
  may 
  be 
  simply 
  ex- 
  

   plained 
  in 
  the 
  following 
  way. 
  If 
  a 
  circulation 
  of 
  air 
  is 
  to 
  be 
  

   set 
  up, 
  air 
  dragged 
  from 
  the 
  neighbourhood 
  of 
  the 
  wire 
  by 
  

   discharge 
  must 
  be 
  returned 
  to 
  it 
  by 
  other 
  paths. 
  The 
  greater 
  

   the 
  uniformity 
  of 
  discharge 
  along 
  the 
  length 
  of 
  the 
  tube 
  the 
  

   less 
  easily 
  can 
  this 
  occur. 
  Now 
  the 
  uniform 
  nature 
  of 
  

   the 
  positive 
  corona 
  implies 
  that 
  the 
  discharge 
  in 
  this 
  case 
  is 
  

   sensibly 
  uniform 
  along 
  the 
  whole 
  length 
  of 
  the 
  tube; 
  whereas 
  

   in 
  the 
  negative 
  corona 
  the 
  glow 
  is 
  concentrated 
  in 
  a 
  number 
  

   of 
  small 
  beads 
  on 
  the 
  wire. 
  Consequently, 
  the 
  circulation 
  

   is 
  more 
  restricted 
  in 
  positive 
  discharge 
  and 
  the 
  cooling 
  

   action 
  of 
  the 
  wall 
  of 
  the 
  tube 
  less 
  effective 
  than 
  in 
  negative. 
  

   This 
  is 
  less 
  noticeable 
  at 
  higher 
  currents 
  when 
  the 
  wind 
  

   pressure 
  gradient 
  causing 
  circulation 
  is 
  steeper 
  ; 
  hence 
  the 
  

   decrease 
  in 
  the 
  value 
  of 
  the 
  ratio 
  under 
  these 
  conditions. 
  

  

  The 
  degree 
  of 
  circulation, 
  other 
  conditions 
  being 
  the 
  same, 
  

   will 
  no 
  doubt 
  depend 
  upon 
  the 
  size 
  of 
  the 
  tube, 
  and 
  this 
  will 
  

   have 
  its 
  effect 
  upon 
  the 
  value 
  of 
  the 
  ratio 
  obtained 
  and 
  

   its 
  dependence 
  upon 
  discharge 
  current. 
  

  

  The 
  results 
  of 
  discharging 
  from 
  the 
  wire, 
  and 
  heating 
  it 
  

   simultaneously, 
  are 
  shown 
  in 
  Table 
  II. 
  (a) 
  for 
  positive 
  and 
  

   Table 
  II. 
  (b) 
  for 
  negative 
  discharge. 
  " 
  w^' 
  and 
  " 
  w" 
  are 
  

   the 
  watts 
  dissipated 
  in 
  discharge 
  and 
  heating 
  current 
  re- 
  

   spectively; 
  u 
  W 
  " 
  is 
  the 
  total 
  watts. 
  As 
  before, 
  " 
  pi—po" 
  is 
  

   the 
  initial 
  rise 
  of 
  pressure. 
  

  

  Table 
  II. 
  

  

  Pi-Ps- 
  

  

  w. 
  

  

  (Pi-J»o)/W. 
  

  

  Observed. 
  

  

  Calculated 
  

   from 
  Table 
  I. 
  

  

  (a) 
  

  

  •18 
  

  

  071 
  

  

  031 
  

  

  •102 
  

  

  1-75 
  

  

  1-66 
  

  

  

  •26 
  

  

  •103 
  

  

  •084 
  

  

  •178 
  

  

  1-46 
  

  

  1-44 
  

  

  

  •38 
  

  

  •158 
  

  

  •137 
  

  

  •295 
  

  

  1-28 
  

  

  1-25 
  

  

  

  •43 
  

  

  •204 
  

  

  •213 
  

  

  •417 
  

  

  1-15 
  

  

  116 
  

  

  

  •56 
  

  

  •263 
  

  

  •256 
  

  

  •519 
  

  

  108 
  

  

  1-12 
  

  

  (b) 
  

  

  •17 
  

  

  •091 
  

  

  •093 
  

  

  •184 
  

  

  •95 
  

  

  •92 
  

  

  

  •28 
  

  

  •157 
  

  

  •138 
  

  

  •295 
  

  

  •94 
  

  

  •90 
  

  

  

  •52 
  

  

  •240 
  

  

  •338 
  

  

  •578 
  

  

  •92 
  

  

  •86 
  

  

  

  •78 
  

  

  •242 
  

  

  •573 
  

  

  •815 
  

  

  •96 
  

  

  •84 
  

  

  (c) 
  

  

  •24 
  

  

  

  •045 
  

  

  •045 
  

  

  55 
  

  

  

  

  •48 
  

  

  

  •094 
  

  

  •094 
  

  

  51 
  

  

  

  

  •66 
  

  

  

  •137 
  

  

  •137 
  

  

  4-8 
  

  

  

  

  119 
  

  

  

  •330 
  

  

  •330 
  

  

  36 
  

  

  

  

  1-98 
  

  

  

  •66 
  

  

  •66 
  

  

  30 
  

  

  

  