A spherical steel ball of 12mm diameter is initially at 100K. It is slowly cooled in a surrounding of 300K. The heat transfer coefficient between the steel ball and the surrounding is 5W/m2K. The thermal conductivity of steel is 20 W/mK. The temperature difference between the centre and the surface of the steel ball is
(a) large because conduction resistance is far high than the convective resistance.
(b) large because conduction resistance is far less than the convective resistance.
(c) small because conduction resistance is far high than the convective resistance
(d) small because conduction resistance is far less than the convective resistance