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:

- resistance change?
- resistivity change?

Justify your answer in each case.

**Answer:**

- Here, length is doubled and area of cross-section is halved. Thus, a wire of length l and area of cross-section A becomes a wire of length 2l and area of cross-section A/2

i.e., resistance becomes four times - 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