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Calculating resistance from voltage drop

  1. May 1, 2010 #1
    On a test in college I was asked to find the current flowing through a resistor and lightbulb on a simple circuit with a battery, resistor and lightbulb. I was told the resistance of the resistor and was given a voltmeter so I measured the voltage across each of the components but when it came to calculating the current I couldn't because I didn't know the resistance of the lightbulb. I'm assuming I could have calculated its resistance since I knew the voltage drop caused by the resistor since I knew the resistance of the resistor. How would you go about calculating the resistance of a component when you know the voltage drop caused by it?
  2. jcsd
  3. May 1, 2010 #2


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    Ohm's law.

    R = E/I
  4. May 1, 2010 #3
    Measure the voltage across the resistor, then I = E/R. Now you know the current through the circuit if it is a series circuit. Measure the voltage across the light bulb, then apply R= E/I.
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