Resistance of fuse wire?

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However as we know, in houses everything is connected in parallel.

Not your fuses (or circuit breakers)! They instead are wired in series with the rest of the load on that circuit. The point of a fire or circuit breaker is to cause the current through the circuit to go to zero in the case of excessive current draw. That wouldn't work if the fuse was wired parallel to the load.

Your intuition that a fuse must have a low resistance is correct. Your confusion results from the incorrect assumption of fuses being wired in parallel with the load (which makes no sense).

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The East Wind
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The East Wind

Updated on March 11, 2020

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  • The East Wind
    The East Wind over 3 years

    Qs. Fuse wires have ______________ melting point and ______________ resistance.

    Fill in the blanks with high and low.

    ----> Well according to me the melting point part is obvious. It will be low melting point as when the temp. increases the fuse melts thus breaking the circuit. The problem arises in the resistance part. I have two logics for this :-

    1) IF the resistance is HIGH, then there will be more obstruction to the passage of current , which would ultimately mean more heat produced in the wire, which would lead to it's melting.

    2)However as we know, in houses everything is connected in parallel. So in this case heat produced is equal to $\dfrac{V^2t}{R}$, i.e. inversely proportional to R. So if the fuse wire has low resistance then automatically the heat generated will be more thus breaking the wire. Also as we know in parallel the current going through the branch is inversely proportional to its resistance. So more current will go through the fuse wire of less resistance, thus generating more heat.

    Confused, I googled the question found it like on 25 websites, but guess what even there there was confusion between people about whether the answer will be low or high resistance. There were like 53% people in favor of high, but i don't know why I think the answer will be LOW. I personally think that the statement

    "more obstruction to the passage of current, which would ultimately mean more heat produced in the wire, which would lead to its melting"

    which i just typed is a bit vague, but i am not sure about this. Also the second logic seems to me to be more mathematically biased, and I trust my Maths more than my Physics.

    Pls give me a definitive answer to this, whether HIGH or LOW, not an answer which can be interpreted in both ways. I have an exam tomorrow, and would want to know what should i mark as the asnwer.

  • The East Wind
    The East Wind over 6 years
    Well no. So i take it that my answer of low resistance is correct, right??