A series motor has a 230 V supply and draws 108 A when running at 555 rpm. The armature resistance is 0.12 Ω and the resistance of the series field winding is 0.04 Ω. For 108 A, consider the flux per pole to be 0.022 Wb and for 46 A, consider it to be 0.017 Wb. (a)Calculate the emf generated when the current is 108 A.

(b)Knowing that E α n* Φ , calculate the new emf generated and the new speed when the motor operates at 46 A.

Steel balls 12 mm in diameter are annealed by heating to 1150 k and then slowly cooled to 400 k in an air att 325 k and h -20 w/m2 k. assume the properties of the steel to be k- 40 w/m k,p 7800 kg/m3, and cp 600 j/kg k. a. determine whether lumped system method can be used to analyze this problem and if so why" b. determine the time required for the cooling process. c. determine the total amount of heat lost from each ball to the ambient air