NEET 2020 Model Question Paper 4

Young's modulus,
Y=

FL

AΔL

=

4FL

πD2ΔL

or ΔL=

4FL

πD2Y

Where F is the force applied, L is the length, D is the diameter and A is the extension of the wire respectively. As each wire is made up of same material therefore their Young's modulus is same for each wire.
For all the four wires, Y, F(= tension) are the same.
∴ΔL∝

L

D2

In (a)

L

D2

=

200cm

0.2cm2

=5×103cm−1
In (b)

L

D2

=

300cm

0.3cm2

=3.3×103cm−1
In (c)

L

D2

=

50cm

0.05cm2

=20×103cm−1
In (d)

L

D2

=

100cm

0.1cm2

=10×103cm−1
Hence, ΔL is maximum in (c)