﻿870 
  Messrs. 
  luller 
  and 
  Grace 
  : 
  Effect 
  of 
  Temperature 
  

  

  centimetre 
  corresponds 
  to 
  a 
  voltage 
  o£ 
  maximum 
  value 
  '00416 
  

   applied 
  to 
  the 
  moving 
  coil. 
  

  

  The 
  induction 
  density 
  in 
  the 
  iron 
  disk 
  was 
  readily 
  calcu- 
  

   lated 
  from 
  the 
  maximum 
  voltage 
  measured 
  as 
  above, 
  the 
  

   dimensions 
  of 
  the 
  search- 
  coil 
  on 
  the 
  iron 
  being 
  known. 
  

  

  The 
  disadvantage 
  of 
  this 
  type 
  of 
  instrument 
  is 
  that 
  the 
  

   constant 
  part 
  of 
  the 
  deflexion 
  depends 
  on 
  the 
  cube 
  of 
  the 
  

   frequency, 
  so 
  that 
  the 
  speed 
  of 
  the 
  machine 
  must 
  be 
  very 
  

   exactly 
  regulated 
  for 
  a 
  constant 
  value. 
  The 
  E 
  M.F. 
  induced 
  in 
  

   the 
  coil 
  on 
  the 
  iron 
  varies 
  approximately 
  as 
  the 
  frequency, 
  and 
  

   so 
  the 
  torque 
  on 
  the 
  galvanometer 
  due 
  to 
  this 
  current 
  depends 
  

   on 
  the 
  square 
  of 
  the 
  speed. 
  It 
  was 
  found 
  better 
  in 
  practice 
  

   to 
  have 
  the 
  two 
  voltages 
  E 
  and 
  E, 
  in 
  opposition, 
  as 
  mentioned 
  

   above, 
  so 
  getting 
  a 
  deflexion 
  proportionate 
  to 
  E^ 
  — 
  E. 
  

  

  One 
  other 
  measurement 
  required 
  to 
  be 
  made, 
  namely, 
  

   that 
  of 
  temperature. 
  This 
  was 
  effected 
  by 
  means 
  of 
  a 
  

   Platinum- 
  Platinum-Rhodium 
  junction 
  (placed 
  close 
  to 
  the 
  

   specimen) 
  connected 
  to 
  a 
  suitable 
  galvanometer. 
  

  

  Fig. 
  3. 
  

  

  15.000 
  

  

  i4 
  

   13 
  

   \l 
  

   11 
  

  

  Is 
  

   I' 
  

  

  3 
  

   2 
  

  

  I 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  / 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  / 
  

  

  107° 
  

  

  c 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  / 
  

  

  / 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  / 
  

  

  / 
  

  

  ^ 
  

  

  ?20° 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  / 
  

  

  /x 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  / 
  

  

  / 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  / 
  

  

  / 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  r 
  

  

  v 
  

  

  

  y 
  

  

  ^ 
  

  

  

  340 
  

  

  ' 
  

  

  

  

  

  

  

  

  

  

  

  ) 
  

  

  y 
  

  

  

  / 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  (A 
  

  

  

  / 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  ^ 
  

  

  y 
  

  

  A 
  

  

  

  

  

  ■»-^ 
  

  

  

  

  

  

  

  

  

  

  

  

  

  >t> 
  

  

  ^ 
  

  

  

  

  

  

  

  \ 
  

  

  450 
  

  

  

  

  

  

  

  

  

  

  

  *^ 
  

  

  y 
  ■ 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  1 
  — 
  

  

  

  

  -—■ 
  

  

  x 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  -fT 
  

  

  

  

  

  

  s. 
  

  

  Sr 
  

  

  ^580 
  

  

  o 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  12 
  13 
  14- 
  15 
  16 
  17 
  18000 
  

   /.voocr/0/v 
  COS 
  urj/TS. 
  

  

  Curves 
  showing 
  relation 
  between 
  Hysteresis 
  Loss 
  and 
  Induction 
  at 
  

   different 
  Temperatures 
  in 
  a 
  sample 
  of 
  armature 
  iron 
  from 
  Messrs. 
  

   Sankey. 
  

  

  The 
  results 
  obtained 
  are 
  shown 
  in 
  figs. 
  3 
  and 
  4. 
  The 
  

   temperature 
  of 
  107° 
  C. 
  was 
  the 
  lowest 
  at 
  which 
  it 
  was 
  found 
  

   possible 
  to 
  make 
  any 
  measurements, 
  on 
  account 
  of 
  the 
  heating 
  

  

  