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Homework Help: Graph of V and I against time in AC

  1. May 12, 2006 #1
    While revising on A.C, I came across the graph of V and I across a resistor plotted against time on the same axis. The book is Serway's College Physics 7th edition. Both curves are sinosoidal and are in phase which I understand, but why does the curve of I is always at a higher amplitude than V? As I know, V = IR, wouldn't the voltage curve have a higher amplitude, that is the peak value of voltage would correspond to a lower peak current for a given resistor? Why in this case is it the other way round?

    Thanks for any inputs.
  2. jcsd
  3. May 12, 2006 #2
    look at the units on that scale. They are not the same. Your question is meaningless. You will see what I mean once you figure out the solution.
    Last edited: May 12, 2006
  4. May 12, 2006 #3


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    Homework Helper

    As Cyrus said, when different units are plotted on the same axis, comparison is meaningless without a scale.

    But even if the axis is specifically drawn such that 1A (one ampere) and 1V (one volt) have the same segment length on the vertical axis, the I curve can be higher than the V curve. Think about what happens when you have a resistance that is less than one ohm.
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