A thin copper wire of length l increases its length by 1% when heated from temperature T1 to T2. What is the percentage change in area when a thin copper plate having dimensions 2l×l is heated from T1 to T2?
2%
We know that, Δl=αlΔT
⇒1100l=αl(T2−T1)
⇒α(T2−T1)=0.01
Now, coefficient of area expansion, β=2α
So, increase in area, ΔA=βAΔT=2αA(T2−T1)
⇒ΔAA=2α(T2−T1)=0.02
Hence, percentage increase in area is 2% and the correct option is (b).