Fuse wires

  • Thread starter Vagrant
  • Start date
  • #1
195
1

Homework Statement



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

Homework Equations



R=pL/a

The Attempt at a Solution


My teacher said no. I think it should because R depends on L


Thanks for your time.
 

Answers and Replies

  • #2
Andrew Mason
Science Advisor
Homework Helper
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Homework Statement



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

Homework Equations



R=pL/a

The Attempt at a Solution


My teacher said no. I think it should because R depends on L


Thanks for your time.
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.

AM
 
  • #3
195
1
Thanks. I think your answer makes sense.
 

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