need help

Discussion in 'General Electronics Chat' started by the teacher, Mar 25, 2008.

  1. the teacher

    Thread Starter New Member

    Mar 25, 2008
    5
    0
    wich one of the following a.c values has the same heating effect as the equivalent d.c value


    A. effective value
    B. average value
    c. peak value
    d. peak-to-peak value
     
  2. sudharshan

    Member

    Mar 3, 2008
    11
    0
    It is P=VAcos(Pi)
    Called as True power
     
  3. the teacher

    Thread Starter New Member

    Mar 25, 2008
    5
    0
    cheers for that answer
     
  4. recca02

    Senior Member

    Apr 2, 2007
    1,211
    0
    An Rms value has the same heating effect as the equivalent d.c value.
    http://www.kpsec.freeuk.com/acdc.htm
    search for RMS on the above site.
    Rms is a type of average value of AC calculated over one cycle.

    True power is something else..It is the active power provided to a load.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
    I was looking for RMS, and didn't see it in the choice list. It varies acording to waveform, but for a sine wave it is 1/square root (2). 120VAC is an RMS value, the peak to peak value would be 120 VAC * Square root(2) * 2, or 336V P-P. The 2 is in the equation because without it we would be talking peak voltage, or one side of the sine wave only.
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Last time I checked, cos(pi) was negative one... Effective (aka RMS) value is peak*sqrt(2), as has already been noted.
     
  7. surbhi

    New Member

    Mar 26, 2008
    5
    0
    A Root Mean Square (RMS) voltage gives the same heating effect as a DC voltage of the same value.
     
  8. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,157
    RMS = effective.

    After all,

     
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