An electric current of 0.25 A flows through a 5-ohm electrical resistor placed in an evacuated chamber. The resistor is a 30-mm-long cylinder with a diameter of 5 mm. Estimate the steady-state surface temperature of the resistor if it has an emissivity of unity (i.e., is black) and the temperature of thechamber walls is 300 K. Neglect any conduction heat transfer through the lead wires.
(this is the setup for the real problem below)
Consider the same situation except that now air at 300 K fills the chamber. Does the steady-state temperature of the resistor increase or decrease? Explain. Estimate the temperature of the resistor if the average convective heat-transfer coefficient is 2.5 W/m^2 * K.