May 2011
Beginner
492 pages
14h 16m
English
Q 1. Two substances P and Q are kept in evacuated vessels maintained at temperatures of 27 °C. Temperatures of P and Q are 627 °C and 227 °C, respectively. Find the ratio of the rates at which heat is lost from the two substances.
Ans. We know that the rate of loss of heat = σ(T 4 − T4o)
where σ = Stefan's constant, T = temperature of hot body, To = temperature of surroundings.
Q 2. A black body of 300 °C is allowed to cool inside an evacuated enclosure surrounded by melting ice at the rate of 0.35 °C/s. lf the mass, specific heat and surface area of the body are 82 gm, 0.01 and 8 sq cm, respectively, calculate Stefan's ...
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