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Homework Help: Voltage and Resistance Exercise, please help.

  1. May 12, 2007 #1
    Please help with the following exercise:

    Given 2 resistors in series R1=10 ohms, R2= 30 ohms, determine the current flowing through the resistors and the voltage across each resistor, if the potential difference across the wire is V=12V.

    This is how I solved it:

    The total resistance Req= R1+R2= 40 ohms

    R = V / i
    i = V/R = 0.3 A

    V(R1) = -R1*i = -10*0.3= -3V
    V(R2) = -R2*i = -30*0.3= -9V

    Is it correct? Can the voltage be negative? Please help.

    Thank you.
  2. jcsd
  3. May 12, 2007 #2
    Voltage can be negative because it is a relative measurement.

    I don't think you did yours right though. Draw the circuit out, and sum the voltages. They should sum to zero because of energy conservation, or otherwise known as Kirchoff's Voltage Law.
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