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Homework Help: Determine the equivalent resistance of the circuit

  1. Apr 5, 2010 #1
    1. The problem statement, all variables and given/known data

    a 3.0 ohm resistor an unkown resistor r and two ammeters a1 and a2 are connected with a 12 volt source ammeter a2 reads a current of 5.0 amperes

    1) detemine the equivalent resistance of the circuit
    2) caculate the current measure of ammeter a 1
    3) caculate the resistance of the unknown resistor r

    2. Relevant equations

    v= 12 v
    a2 = 5.0 a
    a1 = ?
    r1 = 3.0 ohm
    r2 =?

    this is a parallel circuit so

    do i use v/a to find equivalent resistance?

    for current do i use v/r to find a?

    and for the resistor is this equation right 1/req = 1/r1 + 1/r2

    3. The attempt at a solution

    i got 2.4 ohm for the equivalent resistance and 4 a for the current dont know if it right
  2. jcsd
  3. Apr 5, 2010 #2
    There's no way to answer this without seeing the circuit.
  4. Apr 6, 2010 #3
    oh here a picture of the diagram for the problem

  5. Apr 6, 2010 #4


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    Homework Helper

    The answers you have so far are correct. What exactly makes you doubt your solution?
  6. Apr 6, 2010 #5
    You are correct so far, so why not go on to find the resistance of the unknown resistor using the formula you have: [tex]\frac {1}{R_{eq}} = \frac{1}{R_{1}} + \frac{1}{R_{2}}[/tex]
  7. Apr 6, 2010 #6
    ok i got 12 r for the resistor using that equation
  8. Apr 6, 2010 #7
    Which is correct, apart from the units; the units of resistance are Ohms, [tex]\Omega[/tex].
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