High wattage resisters from resistance wire.

[Screech]

Can the wire from 240 Volt, 1200 watt hair dryers make high watt resistors?
The wire looks like a 1/4 inch diameter coil spring. It'a about 2 feet long.
It drops about 1 ohm per centimeter.

If i made resisters out of it, how much power can they handle?
or is it an amp thing?
1200/240=5amps?

 

[Nigel Goodwin]

Can the wire from 240 Volt, 1200 watt hair dryers make high watt resistors?
The wire looks like a 1/4 inch diameter coil spring. It'a about 2 feet long.
It drops about 1 ohm per centimeter.

If i made resisters out of it, how much power can they handle?
or is it an amp thing?
1200/240=5amps?

Yes, you can use the wire to make high wattage resistors, the wattage is very simple to work out - the full element is rated at 1200W, half of it would be rated at 600W - you simply work it out like that!.

Obviously, it may not be desireable for the resistor to get red hot, and you could derate it accordingly - however, the rating of commercial resistors certainly gets the resistors far too hot to touch as well.

I actually use a piece of fire element as a polystyrene cutter, it's about 2 feet long and gets hot enough to cut polystyrene but doesn't glow red off a 24V AC supply.

 

[Screech]

Cool, It will work.
Thanks Nigel.

 

[stevez]

Realize that the heater element handles 1200 watts because it is cooled with a forced flow of air. If you rely on natural convection or elect to enclose the material the amount of heat you can dissapate will be profoundly affected. Note also that if the temperature of the material changes a great deal then the resistance of the material will change significantly. None of this means that you can't use the material as you would like - actually it's a good thought. Experimenting will reveal what you can do with it.

I was lucky enough to find a spool of ni-chrome wire, 28 ga or so, maybe 1000 ft, for $1 at a flea market. Apparently used at some point in applicance repair or for making resistors.

Don't overlook plain old copper wire - or possibly iron (such as a farmer would use in a fence). I recently built a meter shunt so I could get a 5 amp range out of a 500 ma meter. I initially imagined this 100 ft coil but after doing the math I only needed 10 inches. At 5 amps the wire was warm but not hot. You might find that the longer lengths needed, as compared to high resistance wire, allow for better heat dissapation.

 

[Nigel Goodwin]

Realize that the heater element handles 1200 watts because it is cooled with a forced flow of air.

Yes, very true - I didn't notice 'hair dryer' - I was thinking of a radiant fire element which isn't forced air cooled.

 

[pike]

I think nichrome wire would be a better option. It is used mostly for this kind of application (heating elements). It has a much higher resistance. i think it was something like 13 ohms a metre on 18 AWG.