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Using Ohm’s Law

  1. Feb 11, 2010 #1
    1. The problem statement, all variables and given/known data

    Using Ohm’s Law as a check: V = IR, where V = emf in loop, what is the ratio of the current in the loop of radius 20 cm compared to the loop of radius 40 cm?

    (It should be the same as the ratio of the emfs!) Treat the loop as a solid circle and remember the formula for the area of a circle is A = π r2. So if the radius is halved, what does this do to the area? Does this agree with the ratio of the two peak voltages that you calculated? Record your observations and explain.

    2. Relevant equations
    V = IR,

    m = (y2-y1) / (x2-x1)

    3. The attempt at a solution

    I gathered all my data (which is the first part of the question):

    Table 1:
    Loop Radius (cm) Peak Voltage (V)
    10 0.138
    20 0.553
    30 1.244
    40 2.211
    50 3.454

    The data in table 1 is suggesting that as the radius increases, so will the peak voltage.

    So my instructor wants me to check it using Ohm's Law, How exactly would I do that? Here is the question again:

    Using Ohm’s Law as a check: V = IR, where V = emf in loop, what is the ratio of the current in the loop of radius 20 cm compared to the loop of radius 40 cm?

    We have:
    I = V / R = 0.553 / 20 = 0.27650;
    And:
    I = V / R = 2.211 / 40 = 0.55275;

    My instructor is saying that it should be the same as the ratio of the emf's
     
    Last edited: Feb 11, 2010
  2. jcsd
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