1: (25 Points) An electric heater with a total surface area of 0.25 m2 and emissivity 0.75 is in a room where the air has a temperature of 20 oC and wall temperature of 10 oC. When the heater consumes 800 W of electric power, its surface has a steady temperature of 150 oC.
a. Determine the temperature of the heater surface if the heater consumes 1200 W (negligible the radiation).
b. Determine much ermine electrical power the heater consumes when the heater surface has a temperature 200 oC, (Taking radiation in the consideration).