Class 12 NEET Physics Current Electricity Questions Part 1

Resistance of wire =ρ

l

A

R∝

l

A

=

l

πr2

When length and radius are both doubled
R1∝

2l

π(2r)2

⇒R1∝

1

2

R
The specific resistance of wire is independent of geometry of the wire, it only depends on the material of the wire.