power through a resistor question

Discussion in 'General Electronics Chat' started by hunterage2000, May 12, 2010.

  1. hunterage2000

    Thread Starter Active Member

    May 2, 2010
    400
    0
    Can someone tell me how to find power in different resistors once you have the total power?
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Depends on the particular circuit you are considering - do you have something specific in mind?
     
  3. hunterage2000

    Thread Starter Active Member

    May 2, 2010
    400
    0
    lets say 4 parallel resistors R1 = 5 R2 = 7 R3 = 10 R4 = 20 and V = 10.
     
  4. Bosparra

    Member

    Feb 17, 2010
    79
    3
    You need to calculate the current through every resistor and multiply with the voltage across it.
     
  5. sage.radachowsky

    Member

    May 11, 2010
    241
    38
    Current is V/R, and then you're multiplying by V to get power, so you can simplify it to V^2 / R.

    For the 5 Ohm for example, (10 V ^2) / 5 Ohms = 20 W
     
  6. guru200773

    Member

    Apr 26, 2010
    94
    1
    you are wrong Mr.sage.radachowsky.. U have to find out the voltage drop on each resistor in order to use that V^2/R formula not the source voltage..Whatever the formula u want use u need the current.. so I=V/R(eq). R(eq)=R(1)+R(2)+R(3)+R(4)=5+7+10+20=42
    therefore.. I=10/42=0.238A.. Use P=I^2*R formula i.e
    power on R(1) = 0.2822, power on R(2)=0.3965, power on R(3)=0.5664 power on R(4) =1.1328 Add the all power in each resistor then total power is P(t)=2.3779--------------------- eq(1)

    another of finding total power is P(t)= V(source)*I=10*0.238=2.38-------------------- eq(2)
    both eq(1) and eq (2) are equal [eq(1)sightly varies because of rounding off of decimal points in calculations....:):):)]


    If u know the total power and source Voltage.. find current by using I=P(t)/V
    then use formula I^2/R to find the power drop on resistor.....
     
    Last edited: May 12, 2010
  7. sage.radachowsky

    Member

    May 11, 2010
    241
    38
    ... but he said the resistors are in parallel...
     
  8. guru200773

    Member

    Apr 26, 2010
    94
    1
    oh i am extremely sorry dude.. i didnt notice that and Me only wrong.... ITS PARALLEL circuit so what Mr.Sage.radachowsky is absolutely correct sorry dude pls pardon me....:( :(
     
Loading...