Question

A thin copper wire of length L increase in length by
1% when heated from temperature T, to Tg. Whe
is the percentage change in area when a thin
copper plate having dimensions 2L x L is heated
from T, to T?
(A) 1%
(B) 2%
(C)3%
(D) 4%​

Answer 1

Answer

Given:

ΔT=100−0=100°C

ΔL/L=length=L=1%=1/100=0.01

ΔL=αLΔT

ΔL/L=αx100

0.01=αx100

α=0.01/100=1×10

−4

Given Area of copper plate =2LxL=2L

2

By thermal expansion theory,

ΔA=βAΔT

ΔA/A=βΔT

but,

β=2α

ΔA/A=2αΔT

=2×1×10

−

4×100

=2×10

−

2

ΔA/A×100=2×10

−2

×100=2%

Hence,

option (B) is correct answer

Answer 2

(B) 2%
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