Wire Breaking in Elecrtical Circuit

[Nameo]

Why does a fuse wire break as the current increase? I understand why it would heat up, but what causes the wire to break?

[xrayspecs]

The wire heats up to the point where it just desintegrates. it doesn't break in the accepted sense of the word.

[Gef]

It gets hot enough to melt.

[rojash]

As Gef says: take some metal, heat it up, it melts. It doesn't break and it doesn't disintegrate, it just plain melts.

[xrayspecs]

Rojash - disintegrates, melts, what is the difference it still stops working!

[stanleyman]

Actually it can disintegrate if it has been run hot for long periods of overload, it gets thinner until it breaks. That's why fuses sometimes fail for no apparent reason.

[Gef]

Stanleyman, I understand your answer but surely a fuse should "nor run hot for long periods of overload". If that is the case then the wrong rating of fuse is being used which is dangerous.

[stanleyman]

I quite agree Gef that it shouldn't happen but it does sometimes. Excessive overloading of circuits with the right fuse for the cable can happen to cause this as well as fitting too small a fuse especially in plug tops. Cables and fuses are designed to enable quite a large overload for certain periods but if frequently run close to the limit it will weaken the fuse resulting in a premature failure even though well within its capacity at the time.