﻿Roioland 
  and 
  Penniman 
  — 
  Electrical 
  Measurements. 
  47 
  

  

  Substituting 
  the 
  value 
  of 
  Cs;^"^^ 
  in 
  equation 
  (1) 
  and 
  simplify- 
  

   ing, 
  it 
  becomes 
  

  

  Therefore 
  the 
  deflection 
  is 
  proportional 
  to 
  

  

  DaC^C3 
  cos 
  (c^3(^J 
  = 
  C^' 
  '- 
  p^.y_^^.j^.^, 
  — 
  '—^ 
  

  

  where 
  D 
  is 
  the 
  deflection. 
  Therefore 
  the 
  condition 
  for 
  zero 
  

   deflection 
  is 
  

  

  -5^LMRV-^^L"Mr(R+r) 
  = 
  

  

  • 
  * 
  • 
  L" 
  — 
  R" 
  

  

  The 
  condition 
  therefore 
  of 
  zero 
  deflection 
  is 
  independent 
  of 
  

   M. 
  But 
  M 
  is 
  one 
  of 
  the 
  factors 
  of 
  the 
  electromotive 
  force 
  in 
  

   the 
  R^^ 
  circuit, 
  and 
  on 
  it 
  therefore 
  depends 
  the 
  sensitiveness, 
  as 
  

   it 
  determines 
  the 
  current 
  through 
  the 
  H" 
  circuit. 
  In 
  the 
  first 
  

   figures 
  of 
  this 
  method 
  the 
  fixed 
  coils 
  are 
  in 
  the 
  R^^ 
  circuit, 
  and 
  

   the 
  hanging 
  coil 
  in 
  the 
  R 
  circuit, 
  but 
  this 
  is 
  not 
  necessary, 
  as 
  

   the 
  fixed 
  and 
  hanging 
  coils 
  can 
  be 
  reversed. 
  The 
  choice 
  of 
  

   which 
  of 
  the 
  above 
  arrangements 
  should 
  be 
  used 
  depends 
  on 
  

  

  