Approximate number of amps current to heat Ni Cr C wire to 315 C for AWG 10 through 30, according to table at http://cecs.wright.edu/balloon/images/2/22/Nichrome_Wire_Heating_Element_Design_Basics.pdf

ampsfor315C={23.3,19.2,16.1,13.6,11.6,10,8.7,7.5,6.5,5.8,5.1,4.3,3.7,3.3,2.9,2.52,2.14,1.84,1.61,1.41,1.19}

Resistance in ohms per foot at 20 degC for same wire type and gauges.

ohmsperft={0.06488,0.08151,0.1029,0.1302,0.1648,0.2078,0.2595,0.3333,0.4219,0.5208,0.6592,0.8310,1.055,1.322,1.671,2.107,2.670,3.348,4.252,5.286,6.750}

Length[ampsfor315C]

Length[ohmsperft]

Increase in resistance for Ni Cr C at 315 degC

deltaohms=1.052

Power dissipated by one foot of wire at 315 degC

powerat315C=deltaohms ohmsperft (ampsfor315C^2)

ListPlot[powerat315C,DataRange->{10,30}, PlotRange->{{10,30},{10,40}},GridLines-> Automatic,PlotMarkers->{•,Large},Frame->True,BaseStyle->{FontWeight->"Normal",FontSize->14},FrameLabel->{{"Power (W/ft)",""},{"Wire Size (AWG)","Power per foot for Ni Cr C Wire at 315 ˚C"}}]

If we use two feet of 24 AWG, we’ll dissipate about 30 W

p2ft24=2 powerat315C[[24-9]]

We can find the current and voltage for this drive level

a=ampsfor315C[[24-9]]

r=deltaohms ohmsperft[[24-9]]

v=a 2 r