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What is the field strength and when does a situation like this occur?

  1. Mar 22, 2009 #1
    Please help me with the following:

    What is the field strength needed to achieve a current density of 5 x10^4 [Am^-2] in a conductor of resistivity 5 x 10^-8 [Ω m]

    The answer I got was 2.5 x 10^-3 N C^-1

    using the equation J = σ E

    But then I was wondering when a situation like this occurs and this i do not know.

    Thank you for any help
  2. jcsd
  3. Mar 22, 2009 #2
    Thank you for using mks units. because an ohm is one volt per amp, we can multiply 50,000 amps per square meter and 5 x 10^-8 ohm meters (pure copper is 1.72 x 10^-8) and get 0.0025 volts per meter. Suppose 100 amps is run in a conductor 0.01 m by 0.01 m. The resistance would be 5 x 10^-4 ohms per meter. The voltage drop would be 0.05 volts per meter, and the power dissipation would be 5 watts per meter.
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