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Changing Resistance

  1. Jul 9, 2007 #1
    1. The problem statement, all variables and given/known data
    You have a tungsten wire with a certain length and cross-sectional area. This wire has a resistance R. If you wanted to make a new wire with a SMALLER resistance, which of the following changes would accomplish that objective?
    True False use a piece of copper wire instead, with the same length and cross-sectional area
    True False increase the temperature of the wire
    True False use a thicker piece of tungsten wire, with the same length
    True False use a longer piece of tungsten wire, with the same cross-sectional area
    True False decrease the voltage between the ends of the wire


    2. Relevant equations
    V=IR
    R=p(L/A)


    3. The attempt at a solution
    My answers are in bold, atleast one of them is wrong, but i do not know which one, can anyone help out?

    Reason for answers:
    1. Copper wire has a lower p so the R will be lower
    2. Increasing Temp, increases the R
    3. Increases A, which decreases R
    4. Increases L which increases R
    5. R=V/I so a lower V would mean a smaller R

    I cant figure out which answer is wrong, any help?
     
  2. jcsd
  3. Jul 10, 2007 #2
    Anyone know what im doing wrong?
     
  4. Jul 10, 2007 #3

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Think really hard about 5) again. Decreasing V decreases I, not R.
     
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