PHYSICS · Multi-part · CBSE · Physics · Thermal Properties of Matter · Thermal Properties of Matter
Problem
Three identical square metal plates, each of side length 20cm, are mounted in a laboratory so that they can freely radiate energy into a large, temperature–controlled vacuum chamber. Plate A is maintained at an equilibrium temperature of T. Plate B is identical to Plate A except that it is heated until its equilibrium temperature is 2T. Plate C is identical to Plate A except that its emissivity is only 0.20 of that of Plates A and B; Plate C is held at the same temperature T as Plate A.
Throughout this problem neglect any other form of heat transfer and assume that each plate emits uniformly from one side only.
(a) Determine by what numerical factor the rate at which Plate B emits thermal energy exceeds the rate for Plate A.
(b) Determine by what numerical factor the rate at which Plate C emits thermal energy differs from the rate for Plate A. State whether it is greater or smaller and justify your answer qualitatively.
(c) Explain why, for objects of the same size and surface properties, even a modest increase in absolute temperature can cause a large increase in radiated power.