temperature and resistance of fuses

[danaeris]

tired. achey. bed time.

I wanted to write a question relating temperature and current for a fuse, but it doesn't work out. Are fuses non ohmic?

R is proportional to Temperature, and inversely proportional to current. so then temperature should be inversly proportional to current.

But fuses blow when the temperature is high and the current is high... which does not at all imply inverse proportionality.

I tried to look it up online and had no luck. Bah humbug.

I feel so defeated -- by my own weakness. I did nothing other than going to dinner with a friend today (ok, and I watched four episodes of anime), and I still managed to only write a bit less than half a chapter test.

I think I need to stop thinking about having to get things done and just try to enjoy the work itself and do my best job. If I let myself focus on the work and not the time passing by, maybe I'll start enjoying it and thus my focus will improve and the work will go faster.

I fall down go boom.

Comments

So.

[earthdragon.livejournal.com]

Resistance, tends to increase with temp. but in nornal ranges, not dramatically so. In normal situations, it is treated as a constant. I've never seen a situation where R was driven using Ohms law.

Power is what turns into heat and generates a temp. figuring out the exact relationship requires knowing the situation and some thermo, but can be aproximated as k(T_hot - T_Ambient).
So Temp ~ K Power + C = K(i^2R)+ C = KRi^2 + C.
So Temp is roughly perportional to i^2, and when there is too much current, the fuse melts and does the right thing.

BTW, fun demo, get a Kit-Kat wraper, cut our the middle leaving a small, (1/8th of an inch, 3-4mm wide, 1/2 inch long or 1 cm long) bridge connecting the whole of the two sides. Now wire each end of the wraper to a decent batteery(it might take a few, its been a while), and watch the fuse Flashmelt.