# Investigating Fuses

1. Mar 3, 2008

### O_oSam

I have just started a Physics project which I have already missed the deadline for >_<

I have a very minimal set of results, I basically took a power supply>smoothing unit and put them in a circuit with a component holder and two resistors (in parrallel so I didnt blow the ammeter) and took readings.

Was wondering if I could get some helpful information etc. on fuses. Can anyone give me a detailed explanation of why fuses melt, I was hoping to tie in Electrical resistivity [I'm aware it changes as fuse heats] and possible thermal conductivity?

Does the thermal expansion of a wire have any relevance?

Thanks

Sam

2. Mar 4, 2008

### chaoseverlasting

Im not sure if I should tell you this, because its obviously something you should do yourself.

Fuses melt because the heat generated in them increases the temperature of the fuse wire beyond the melting point. The heat generated is equal to $$dh=i^2Rdt$$ and R is related to resistivity by the expression $$R=\rho \frac{l}{A}$$, where A is the cross sectional area, $$\rho$$ is the resistivity and l is the length of the wire under consideration.