Resistance Wire and AC/DC Electrics.

[pjl83]

I've been working on a project that I posted on here a while ago. I was looking at using resistance wire to make a heated stirring attachment.

 

I am now ready to build a tester to try out my theory.

 

Using W=V2/R I worked out that using 230v I would need 6.3 ohm/metre to achieve my 100 watt target based on the total length of the wire needed.

 

However, I found examples of this equation being used accurately with DC electrics. Would the resistance wire behave the same with AC ?

 

If not, then how do I work out this equation using AC?

 

Any thoughts would help on this......................

 

Thankyou in advance!

[Cap'n Refsmmat]

If your wire does not have any inductance or capacitance (if it's regular copper wire, it likely has negligible amounts), the equations behave the same way. However, since the voltage varies with time, you'll get an average power.

 

I'm not entirely sure about that, though.

[pjl83]

Thanks,

 

It's ni-chrome resistance wire. If the equation is the same then I could calculate the wattage using the RMS value from a voltmetre at supply then maybe?

[Cap'n Refsmmat]

Yes, you'd have to use the RMS value of the voltage. I think that should work.

 

My experience with AC has been a few weeks of class a month or two ago, so I might be wrong, of course.

[swansont]

If the wire is coiled as in toaster heating elements, you might have to worry about the inductance.

[pjl83]

it will be wound approx. 3mm diametre with each coil around 4mm apart, this was what I was basing my length measurement on.

 

Do you think this may cause problems with inductance? there will be and insulator through the middle of the coils and insulated on the utside too.

 

What do you guys think?

 

thanks

[Externet]

At 50 Hertz and no core, difference will be negligible. Variations from mains voltage are greater factor than what such minuscule inductance can affect.

If you are really trying to eliminate inductance, make half the windings clockwise and half counterclockwise.

[Newbies_Kid]

CR of copper and AL wires can be found in IEC 228