Question

Assertion (A) :When the radius of a copper wire is doubled, its specific resistance increases
Reason (R) :Specific resistance is independent of cross-section of material used

• A. Both A & R are true and R is the correct explanation of A
• B. Both A & R are true and R is not a correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Answer 1

The correct option is D A is false but R is true

Specific resistance is the inherent property of A material , it is defined as a resistance offered by unit length and unit cross section area of the material when a known voltage is applied at the ends.

hence it is a fixed value for a same material of different dimensions.

$\therefore$ unless the material is not changed ,the specific resistance( also called resistivity ) of the material will not change.

Hence, specific resistance is independent of radius and length of wire or conductor.