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ac instantaneous and rms value

AC Instantaneous  and  RMS Value:

 Instantaneous  Value: 
                 The  Instantaneous  value  of  an  alternating  voltage  or  current  is  the  value  of  voltage  or current  at  one  particular  instant.  The  value  may  be  zero  if  the  particular  instant  is  the  time  in  the cycle  at  which  the  polarity  of  the  voltage  is  changing.  It  may  also  be  the  same  as  the  peak  value, if  the  selected  instant  is  the  time  in  the  cycle  at  which  the  voltage  or  current  stops  increasing  and starts  decreasing.  There  are  actually  an  infinite  number  of  instantaneous  values  between  zero  and the  peak  value. 

RMS Value: 
               The  average  value  of  an  AC  waveform  is  NOT  the  same  value  as  that  for  a  DC  waveforms average  value.  This  is  because  the  AC  waveform  is  constantly  changing  with  time  and  the heating  effect  given  by  the  formula  (  P  =  I  2.R  ),  will  also  be  changing  producing  a  positive power  consumption.  The  equivalent  average  value  for  an  alternating  current  system  that  provides the  same  power  to  the  load  as  a  DC  equivalent  circuit  is  called  the  "effective  value".  This effective  power  in  an  alternating  current  system is  therefore  equal to: (  I2.R.  Average). As  power  is  proportional  to  current  squared,  the  effective  current,  I  will  be  equal  to  √  I  2  Ave. Therefore,  the  effective  current  in  an  AC  system is  called  the Root  Mean  Squared  or  R.M.S. 


                 

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