﻿50 
  Rowland 
  and 
  Penniman 
  — 
  Electrical 
  Measurements. 
  

  

  Correction 
  due 
  to 
  hanging 
  coil. 
  The 
  self-inductance 
  ='0164 
  

   henry 
  of 
  the 
  fixed 
  coils 
  gives 
  a 
  correction 
  of 
  —14-55 
  ohms, 
  

   therefore 
  the 
  self-inductance 
  '0007 
  henry 
  of 
  the 
  hanging 
  coil 
  

   gives 
  a 
  correction 
  of 
  —'62 
  ohms 
  to 
  the 
  R-f^ 
  circuit. 
  Apply- 
  

   ing 
  these 
  corrections, 
  the 
  results 
  obtained 
  for 
  the 
  several 
  coils 
  

   under 
  various 
  conditions 
  are 
  given 
  below. 
  The 
  results 
  are 
  

   given 
  in 
  the 
  following 
  order. 
  

  

  First. 
  The 
  values 
  are 
  calculated 
  using 
  double 
  leads 
  in 
  the 
  

   circuits 
  but 
  open 
  resistances 
  as 
  far 
  as 
  possible. 
  

  

  Second. 
  The 
  variation 
  of 
  the 
  apparent 
  value 
  of 
  the 
  self- 
  

   inductance 
  of 
  one 
  of 
  the 
  coils 
  with 
  different 
  positions 
  of 
  the 
  

   coil, 
  resistances, 
  and 
  different 
  kinds 
  of 
  leads. 
  

  

  Third. 
  Short 
  leads 
  separated 
  about 
  6 
  inches 
  and 
  crossed, 
  

   used 
  with 
  all 
  the 
  coils 
  except 
  B^. 
  

  

  Fourth. 
  Open 
  leads 
  and 
  open 
  resistances 
  in 
  the 
  determina- 
  

   tions. 
  In 
  the 
  table 
  ^" 
  was 
  open 
  resistance 
  plus 
  the 
  resistance 
  

   of 
  coil 
  B, 
  and 
  fixed 
  coils 
  of 
  instrument. 
  R-t-^^ 
  was 
  made 
  up 
  of 
  

   the 
  small 
  coil 
  and 
  open 
  resistance 
  plus 
  the 
  amount 
  in 
  the 
  Queen 
  

   ordinary 
  resistance 
  box. 
  

  

  After 
  all 
  the 
  inductive 
  effect 
  of 
  the 
  leads 
  was 
  removed 
  and 
  

   the 
  ordinary 
  resistance 
  box 
  used 
  as 
  little 
  as 
  possible, 
  there 
  was 
  

   a 
  different 
  value 
  obtained 
  for 
  the 
  ratio 
  of 
  the 
  self-inductances 
  

   dependent 
  on 
  the 
  position 
  of 
  the 
  reversing 
  commutator 
  A^ 
  

   With 
  all 
  the 
  coils 
  used 
  the 
  greater 
  value 
  occurred 
  with 
  the 
  

   same 
  position 
  of 
  A^ 
  This 
  was 
  due 
  to 
  the 
  electrostatic 
  action 
  

   between 
  the 
  coils 
  B, 
  and 
  B^, 
  for 
  if 
  the 
  terminals 
  of 
  the 
  coil 
  B^ 
  

   and 
  the 
  commutator 
  A^ 
  were 
  reversed 
  at 
  the 
  same 
  time, 
  there 
  

   was 
  no 
  change 
  in 
  the 
  value 
  of 
  the 
  ratio 
  of 
  the 
  inductances. 
  

   This 
  showed 
  that 
  it 
  was 
  dependent 
  on 
  the 
  coil 
  itself 
  and 
  not 
  on 
  

   the 
  leads 
  and 
  it 
  could 
  therefore 
  not 
  be 
  eliminated. 
  

  

  It 
  is 
  to 
  be 
  noticed 
  that 
  the 
  values 
  obtained 
  for 
  the 
  lower 
  

   number 
  of 
  alternations 
  are 
  always 
  greater 
  than 
  those 
  found 
  

   with 
  the 
  higher 
  number 
  of 
  alternations. 
  This 
  was 
  caused 
  by 
  

   the 
  electrostatic 
  action 
  of 
  the 
  turns 
  of 
  the 
  coil 
  on 
  each 
  other. 
  

   In 
  the 
  case 
  of 
  the 
  coil 
  P2 
  this 
  effect 
  would 
  be 
  caused 
  by 
  suppos- 
  

   ing 
  a 
  capacity 
  of 
  '0007 
  microfarads 
  shunted 
  across 
  the 
  terminals. 
  

  

  The 
  results 
  are 
  now 
  given 
  comparing 
  the 
  different 
  coils 
  with 
  

   Bj 
  as 
  a 
  standard 
  and 
  equal 
  to 
  1 
  henry. 
  

  

  Double 
  Leads 
  of 
  Bell 
  Wire 
  and 
  Opex 
  Resistances. 
  

   r 
  = 
  106 
  ohms, 
  n 
  = 
  45 
  complete 
  periods 
  per 
  second. 
  

  

  

  

  

  

  

  

  Cor- 
  

  

  Aver- 
  

  

  Com. 
  

  

  

  Coils. 
  

  

  R". 
  

  

  Correc. 
  

  

  

  Queen. 
  

  

  R-hr. 
  

  

  rec. 
  

  

  age. 
  

  

  A'. 
  

  

  Ratio. 
  

  

  Pi-hP^ 
  

  

  

  

  

  

  

  

  

  

  

  + 
  

  

  901-6 
  

  

  -14-55 
  

  

  887-05 
  

  

  292 
  

  

  2300-2 
  

  

  -•62 
  

  

  2304-9 
  

  

  1 
  

  

  2-5983 
  

  

  

  

  u 
  

  

  

  310 
  

  

  231 
  10 
  

  

  

  

  2 
  

  

  

  c 
  

  

  

  u 
  

  

  

  19 
  

   22 
  

  

  11583 
  

   1161-2 
  

  

  

  1159-0 
  

  

  1 
  

   2 
  

  

  1-3099 
  

  

  + 
  P, 
  

  

  

  u 
  

  

  

  103 
  

  

  1659- 
  

  

  

  1661-2 
  

  

  1 
  

  

  1-8727 
  

  

  u 
  

  

  

  (1 
  

  

  

  109 
  

  

  1664-8 
  

  

  

  

  2 
  

  

  

  