# fuse blown up

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I connected a piece of nichrome wire( heating element) the one u'll find in old electric stoves ~4cms (don't know its resistance exactly) to Ac current. when I switched on, fuse was blown up in my home. Does the fuse blown due to

1. short circuit or

If what I did (connecting ni-cr wire directly) was wrong then are there any circuits for connecting it AC mains. Any suggestions

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don't go near anything electrical, you're not there yet...

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I'm no expert on fuses but here's what I know (or think I know : ) )

A fuse is like a light bulb. If it's overdriven with current...it heats up, melts and/or oxidizes? . That's the burn out. P=I^2R where R is the fuse element. R increases with temperature like most conductors. When P is sufficient for making the fuse element reach the melting temperature ..it blows.

Your fuse blows because it can't sustain the current for your circuit. D from BC

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Um, its important to know the resistance. The resistance tells you how much current is going to be pulled and hence you then can determine if the breaker will blow/fuse will go.

Since the voltage in AC mains is ~120Vrms AC, by ohms law

120Vrms / R = I

So if R = 0.001ohm then your pulling 120k Amps. The average outlet in a house only lets about 15A through.

If R = 1 ohm, then I = 120 Amps and this is still to large.

I believe most electrical stoves run in houses run on a seperate branch that allows more current(which means they must have larger wires or better insulated wires) to pass.

In any case you need to measure the resistance.

If the resistance is large enough(say > 10 ohms) then it should be ok. Make sure you don't have any other current hungry devices connected on the same branch though. If you have a two friges, a stove, a TV, 2 lamps, a computer, etc... all connected to the same socket then your going to trip the breaker or burn down your house.

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Look at it this way. Suppose the full length of the nichrome wire was 40 cm. You cut off 4 cm of that. If the whole 40 cm draws 5 amps, then your 4 cm was trying to draw 50 amps.

Tam

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How can you know what the resistance is going to be after it gets hot until you've tried it? Maybe a variac would help, but measuring the cold resistance doesn't reveal much.

```--
zero, and remove the last word.```
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Are you sure that it was not blown *down* ?? Methinks that wire was rather short, and most definitely drew at least 3 times the fuse rating.

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Stoves in the US do take a lot of current; they run off of 220V to decrease cut current loading on the power line.

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With a short piece, that would be an excellent way to ruin the variac, if it is not fuse protected.

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And if the fuse did not blow, that short piece of nichrome would have gone blooey, spitting a few drops of molten nichrome in the process. Or the wires to that piece of nichrome might have done that instead. This experiment sure sounds like a fire hazard to me!

If you use 1/10 the length of a heating element, you will be dissipating into it 10 times the amount of power that the full length takes (give or take due to variation of resistance with temperature). 100 times rated power per unit length (or whatever in this ballpark it turns out to be) is going to blow *something*!

- Don Klipstein ( snipped-for-privacy@misty.com)

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Something I found on the NET for all to look at on this subject..

```--
"I\'d rather have a bottle in front of me than a frontal lobotomy"
http://webpages.charter.net/jamie_5```
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The OP never exactly said if he used the whole 120V length or not.

```--
zero, and remove the last word.```
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It doesn't matter. Resistance doesn't decrease with temperature so it will pull max current when cold. Also, Nichrome has a very small coefficient so there is very little change.

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Yes he did - he stated a 4cm length.

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Yes - if you do any more experiments, video the event and post on youtube with the link here.

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skrev i en meddelelse news: snipped-for-privacy@s12g2000prg.googlegroups.com...

Replace wimpy Fuse with Nail Try Again Perhaps try bigger nail