Hi. I want to calculate the energy requirements and temperature increase of 3 inches (75mm) of 22AWG Nichrome wire.

Referring

here. 3" of 22AWG Nichrome, requires approx 0.5 amps to increase its temperature by 20C (68F). The resistance through the wire is ~0.25R, and increase in R due to heating up to 20C very small - assuming zero.

E = IR

E = 0.5*0.25= 0.125v, is the voltage required to provide 0.5amps to a wire with a resistance of 0.25R and heat it 20C (68F) from 0C (32F). In which case given the very small R values in question, raising the temperature of the wire by 20C from any other temperature state, will require the same current and voltage.

P = IE

P = 0.5*0.125 =

~~0.0625~~ ~~Joules~~ 0.0625watts.

It makes sense that the energy required to heat 3" of 22AWG wire will be quite small. I'm wondering if my calculations are correct? Not included, is the additional energy to warm a small flat glass component, 22mm x 15mm x 0.8mm to which the Nichrome will be attached.

The plan is to schedule power using PWM switching a logic level mosfet.