KCET 2021 Physics Solved Paper

given, resistance, R1=3Ω
If l is the original length of the wire, then after stretching the length of wire is
l′=2l
From the relation, resistance of a wire,
R=ρ

1

A

where, ρ is the resistivity and A is cross-sectional area.
R∝

l

A

⇒ R∝

l2

V

[∵A=

Volume

Length

]
⇒

R1

R2

=

l12

V

×

V

l22

Here, l1=l,l2=2l
⇒

3

R2

=

l2

4l2

or R2=3×4=12Ω