Question

If length of a wire is doubled and areas is halved what will be change in specific resistance ?

Answer 1

Answer:

Explanation:

Imagining a circular wire of length l and radius r

R∝lπr2

Therefore,

R2R1=l2l1(r1r2)2

We have r2=r12 and l2=2l1

R2=8R1

New resistance is 8 times the old resistance.

Answer 2

Resistance R=α l/A

α is specific resistance, l is length and A is area

Specific resistance doesnt depend upon dimensional factors and if length and cross sectional area is changed the resistivity remains constant unless the material is changed.