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Maximum Voltage

  1. Mar 31, 2010 #1
    1. The problem statement, all variables and given/known data
    Three 100ohm resistors are connected as shown. The maximum power that can safely be dissipated in any one resistor is 25W

    What is the maximum potential differencethat can be applied between points A and B.


    2. Relevant equations
    Ohms Law, V=IR
    P=V^2/R

    3. The attempt at a solution
    I simplified the circuit down until I had one single resistor of 150ohm then used P=V^2/R, so 25= V^2/150, rearranged and got V=61V however this is incorrect.
     

    Attached Files:

  2. jcsd
  3. Mar 31, 2010 #2
    That's not quite right. What you're doing is finding the potential across the equivalent resistor. The equivalent resistor doesn't have the same power rating. You should find the max current that can go through the first resistor because it will be what limits you.

    P=I^2R

    So now you know the max current, and you can find the voltage that goes between the equivalent resistor.

    V=IR

    Does that make sense to you?
     
  4. Mar 31, 2010 #3
    Okay the max. current that will go through X is 0.5A.The equivalent resistor is 150ohms so 150*.50 = 75V. Thankyou! the answer is right
     
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