a 4. When conduction occurs in the radial direction in a solid rod or sphere, the heat flux must be zero at the center (r= 0) in order for a finite temperature to exist there. Hence, an appropriate boundary condition is: dT = 0 at r = 0 dr Consider a solid sphere of radius R with a fixed surface temperature, Tr. Heat is generated within the solid at a rate per unit volume given by g = 1; +Tyr; where I and r, are constants. (a) Assuming constant thermal conductivity, use the conduction equation to derive an expression for the steady-state temperature profile, T(), in the sphere. (b) Calculate the temperature at the center of the sphere for the following parameter values: R=3 m =20 W/m Tr=20 C -0.5 W/(mK) Ty=10 W/m