question_answer

  A wire of length L and resistance R is stretched so that its length is doubled and the area of cross-section is halved. How will its: (a) resistance change?               (b) resistivity change? Justify your answer in each case.

Answer:

                  (a) Here, length is doubled and area of cross-section is halved. Thus, a wire of length  and area of cross-section A becomes a wire of length  and area of cross-section Using                                           New resistance,                                                                                       i.e., resistance becomes four times (b) Resistivity of a substance does not depend on its length or area of cross-section. It depends on the nature of the material and temperature. Hence there is no change.