A long wire of diameter D = 1 mm is submerged in an oil bath of temperature T∞ = 25 C. The wire has an electrical resistance per unit length of R'e = 0.01 ohms/m. If a current of I = 100 A flows through the wire and the convection coefficnt is h=500 W/m2 K and steady-state temp of the wire of 88.7 C? From the time the current is applied, how long does it take for the wire to reach a tempature that is within 1 C of the steady-state value?
Properites:
density = 8000 kg/m3 ; c = 500 j/kg K ; k = 20 W/m K.