A blacksmith heated a metal whose cubic expansivity is 6.3 x 10^-6K−¹. The areal expansivity is?

A. 2.0 x 10^-6K^-1
B. 2.1 x 10^-6K^-1
C. 4.2 x 10^-6K^-1
D. 6.3 x 10^-6K^-1

Correct Answer:

Option C = 4.2 x 10^-6K^-1

Explanation

If the lineal expansivity = ∝
=> area expansivity β= 2∝.
And cubic expansivity δ = 3∝.
=> 6.3 x 10^-6 = 3∝
∴ ∝ =

∴ ∝ =	6.3 x 10^-6	= 2.1x 10^-6
	3

∴ Area = 2∝ = 2 x 2.1×10^-6
= 4.2 x 10^-6K^-1