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Homework Help: Electricity - Series and Parallel Circuit

  1. Feb 12, 2010 #1
    1. The problem statement, all variables and given/known data

    A 22-ohm resistor and a 33-ohm resistor are connected in series and placed across 120-V potential difference.

    1. what is the equivalent resistance of the circuit?

    2. what is the current in the circuit?

    3. what is the voltage drop across each of resistor?

    4. What is the voltage drop across the two resistors together?

    2. Relevant equations

    R = RA + RB
    I = V source / RA + RB
    VA = IRA
    VB = IRB

    3. The attempt at a solution

    1. what is the equivalent resistance of the circuit?
    R = RA + RB
    R = 22-ohm + 33-ohm
    R = 55-ohm

    2. what is the current in the circuit?
    I = Vsource/ RA + RB
    I = 120/ 55 = 2.2 A

    3. what is the voltage drop across each of resistor?

    VA = IRA
    = 48.4 V

    VB = IRB
    = 70.4 V

    4. What is the voltage drop across the two resistors together?
    - Ok, they are asking for the voltage drop across the two resistors together. I think you would have to add the two resistors but then should i divide it by the number of volts. But I know you would have to add the total of resistors.
     
  2. jcsd
  3. Feb 12, 2010 #2

    rock.freak667

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    Homework Helper

    Yes you would just add them. Ideally, the sum voltage drops would be the same as the source voltage. (Kirchoff's 2nd law for circuits)
     
  4. Feb 13, 2010 #3

    ehild

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    Homework Helper

    Recalculate I*RB.
    The voltage drop across the two resistors together is the sum of voltages on each resistor.

    ehild
     
  5. Feb 13, 2010 #4
    Yes to ^. With the source voltage being the 120 V.
     
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