question_answer

                                     The resistivity of iron is\[1\times {{10}^{-7}}\,ohm-m\]. The resistance of a iron wire of particular length and thickness is 1 ohm. If the length and the diameter of wire both are doubled, then the resistivity in \[ohm-m\] will be                          [CPMT 1983; DPMT 1999]

A)                    \[1\times {{10}^{-7}}\]

B)            \[2\times {{10}^{-7}}\]

C)                    \[4\times {{10}^{-7}}\]     

D)            \[8\times {{10}^{-7}}\]