parallel Resistors

Discussion in 'General Electronics Chat' started by superway, Apr 29, 2010.

  1. superway

    Thread Starter Active Member

    Oct 19, 2009
    128
    0
    Hello,

    I want to connect 2 parallel resistors: 50 Ohm, 200W and 10 ohm, 40W to load at 60Vac. Does it affect anything for this setup due to different powers watts?
    Thanks.

    ken
     
  2. kkazem

    Active Member

    Jul 23, 2009
    160
    26
    Sorry man,

    You've got a problem here depending whether you put the resistors in series or parallel. If you put them in series, the voltage across the 10 OHM will be:
    60V*10/(50+10) = 10 volts. Now, 10 volts across a 10 Ohm resistor is 1 watt and you have a 10W part--no problem. But if you put them in parallel across the 60V, then you have 60^2/10 = 360 watts dissipated and you only have a 10 watt part. In short, it will fry almost immediately.

    Just to let you know, you should never use a resistor at more than 50% of its power rating on a continuous basis. For short periods of time like a few seconds or less, its OK to go up to the resistors power rating, but it is important not to exceed it as it will cause damage to the resistor.
    Good luck,
    Regards,
    Kamran Kazem
     
  3. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Can you sketch the circuit you are working with so that we can see the whole problem?

    hgmjr
     
  4. superway

    Thread Starter Active Member

    Oct 19, 2009
    128
    0
    Thanks for your help.
     
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