| MadSci Network: Physics |
Hi David, Most materials expand when heated. The coefficients for metals can be found in the Handbook of Chemistry and Physics, which most libraries should have. The shere, when heated uniformly, will expand at the same rate in all directions, so the volume at the center will decrease. The coefficient of expansion for iron is 12 parts per million per degree centigrade, so the change in volume that results from heating the sphere will be very small. Caution! This experiment could be very dangerous. A one foot diameter sphere will not heat uniformly without very special equipment. As the temperature gradient builds up within the sphere it creates a stress gradient. Some metals can actually explode when the thermal stress exceeds the tensile strenght of the material. A more pronouned change in the inside of the sphere will result from heating of the gas at the center. The change in pressure is directly related to the change in temperature. The pressure will increase very quickly as the sphere is heated! Bob Novak Specialist, Process R&D Carpenter Technology
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