# Voltage for NiChrome?

Will 2.5 volts be enough to heat a small segment of NiChrome wire up to/over 100 C? If it helps, the power is coming from a 8.1 kJ 2.5v 2600 F super capacitor which can unload very quickly.

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steveastrouk6 years ago
2.5 Volts, into 1.4 Ohm, is 2.5^2/1.4 W, or 4.4W., or 4.4J/sec. That will last a fair time - 2600 J/ 4.4 J/sec= 590 seconds, or 10 seconds shy of 10 minutes.

How HOT it will get is complicated, but if you assume its completely lossless - you can work out how long it will take to warm up, if you know the thermal mass, which is the mass x specific heat capacity, and you assume a rise in temperature of 100 C then Joules needed = mass x SHC x 100.

Steve
lemonie6 years ago

Yes.
But if you want to know "how long is a piece of wire" then you'll have to tell us what wire it is. Also - for how long, and how much heat do you want to take out of it?

http://www.aircraftmaterialsuk.com/data/electronic/alnicr.html

L
LiquidLightning (author)  lemonie6 years ago
About 1cm long, 18 gauge, NiChrome, about 3-4 seconds, and 2.6 kJ.
6 years ago
Should be quite achievable in energy terms, if I read the wire gauge right it'd be ~1.4 ohm per metre, giving you 0.014 ohm for 1cm.
But that means you'd need to limit current or it'll get too hot very quickly (or will it? for a single-use ignition it'd work)
Maybe some constant-current supply, but at low voltage I don't know.

L
LiquidLightning (author)  lemonie6 years ago
The wire won't be bare, it would be in a small amount of water.
6 years ago

That makes a difference. You're really asking about heating water then -
How much water?

L
LiquidLightning (author)  lemonie6 years ago
No, I'm not asking about heating water, I need the actual wire to get hot, but not above 100 C. The water is just there as a coolant for it to not exceed 100 C.
6 years ago

Water has a high heat-capacity, in terms of how hot things get with current water makes a big difference.
What's it for?

L
6 years ago
The "2.6kJ" is almost irrelevent, because thermal mass here is insignificant.

Steve
Kiteman6 years ago
It depends how thick the wire is.

LiquidLightning (author)  Kiteman6 years ago
18 gauge.
frollard6 years ago
depends on the resistance = amps = watts = energy, which can be used to determine the temperature change of a given weight of wire at a certain heat capacity.

ohms law