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Calculate radius of a copper wire

Discussion in 'Electronics Homework Help' started by Mark Wambua, Oct 2, 2016.

  1. Mark Wambua

    Mark Wambua

    5
    1
    Oct 2, 2016
    Calculate the radius of a copper wire dissipating heat of 100mW given the volume of the conductor is 20mm cubed and is carrying a current of 40nA. Resistivity of copper is 0.0000172.
     
  2. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    A please and thank you wouldnt go a miss, we are human and do this for free you know. Why do people think they can just post a thread like this and get help.
    Adam
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Because we (the world generally) owe them an answer, and because being polite adds a few keystrokes and takes a few seconds that they'll never get back. The same argument applies to why they fail to read the bold print indicating what we will and will not do in this section.
     
  4. duke37

    duke37

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    Jan 9, 2011
    There must be some units for resistivity. I tend to use basic S.I. units for calculations
    Derive an equation for the resistance of a circular wire of nominal length and diameter, Calculate its volume.

    Power dissipated is I*I/R so you can calculate the resistance and solve the equation you derived
     
  5. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Very True Steve.
     
  6. Mark Wambua

    Mark Wambua

    5
    1
    Oct 2, 2016
    Peace guys!
    Am so sorry for lacking courtesy
    Will try to be courteous from now hence forth
    Thousand apologies!
     
    Arouse1973 likes this.
  7. Mark Wambua

    Mark Wambua

    5
    1
    Oct 2, 2016
    would someone hel[ me Calculate the radius of a copper wire dissipating heat of 100mW given the volume of the conductor is 20mm cubed and is carrying a current of 40nA. Resistivity of copper is 0.0000172 ohms mm.
     
  8. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Are you sure it's nA and not mA. That's going to need to be very large in resistance. Also as this is homework, how far have you got yourself. Can you show us your work so far?
    Adam
     
  9. Mark Wambua

    Mark Wambua

    5
    1
    Oct 2, 2016
    [​IMG] I have done a bit and got stuck. It is nA Adam. See attached screen shot.
     
    Last edited: Oct 4, 2016
  10. davenn

    davenn Moderator

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    Sep 5, 2009
    screen shot not showing try uploading again
     
  11. Mark Wambua

    Mark Wambua

    5
    1
    Oct 2, 2016
    Okay
    reattached again.
     

    Attached Files:

  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
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    Jan 21, 2010
    Currently you've gone one step too far. You want the equation describing the resistance in terms of the wire's diameter and length.

    Also, given the power and current, can you calculate resistance?

    Putting these together you'll have an equation with 2 unknowns.

    Do you have sufficient information to state either diameter or length in terms of the other?
     
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