1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Fuse wires

  1. Feb 8, 2007 #1
    1. The problem statement, all variables and given/known data

    does the length of the fuse wire influence its cpacity? why?

    2. Relevant equations


    3. The attempt at a solution
    My teacher said no. I think it should because R depends on L

    Thanks for your time.
  2. jcsd
  3. Feb 8, 2007 #2

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    I think I would agree with your teacher. The fuse capacity (the largest current permitted to flow) depends on the temperature of the fuse wire. At a certain temperature, it melts and stops the current. Off hand, I would say that the temperature depends upon the power density being dissipated in the fuse wire (power / unit volume). The power dissipated is [itex]I^2R = I^2\rho L/A [/itex]

    Now, the power per unit volume is:

    [tex]P/Vol = P/LA = I^2\rho L/A(LA) = I^2\rho/A^2[/tex]

    So it appears to me that the L falls out and the temperature depends entirely upon the cross sectional area of the fuse wire.

  4. Feb 8, 2007 #3
    Thanks. I think your answer makes sense.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook