Physics-
General
Easy

Question

Two circular discs A and B with equal radii are blackened. They are heated to some temperature and are cooled under identical conditions. What inference do you draw from their cooling curves?

  1. A blankand B have same specific heats    
  2. Specific heat of A blankis less    
  3. Specific heat of B is less    
  4. Nothing can be said    

The correct answer is: Specific heat of A blankis less


    According to Newton’s law of cooling, rate of cooling is given by
    open parentheses fraction numerator negative d T over denominator d t end fraction close parentheses equals fraction numerator e A sigma over denominator m c end fraction left parenthesis T to the power of 4 end exponent minus T subscript 0 end subscript superscript 4 end superscript right parenthesis
    Where c is specific heat of material.
    or open parentheses fraction numerator negative d T over denominator d t end fraction close parentheses proportional to fraction numerator 1 over denominator c end fraction
    i e. comma blankrate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.

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