An air heater may be fabricated by coiling Nichrome wire and passing air in cross flow over the wire. Consider a heater fabricated from wire of diameter 1mm, electrical resistivity 10-6 O m, k=25 W/m K and e=0.2. The heater is designed to deliver air at a temperature of 50°C under flow conditions that provide a convective coefficient of 250 W/m2K for the wire. The temperature of the housing that encloses the wire and through which the air flows is 50°C if the maximum allowable temperature of the wire is 1200°C, what is the maximum allowable electric current I? If the maximum available voltage if 110 V, what is the corresponding length of the wire that may be used in the heater and the power rating of the heater? Assume negligible temperature variations within the wire.