Metal rods of length 20m each are laid end to end to form a bridge at 25oC. What gap will be provided between consecutive rails for the bridge to withstand 75oC?
[Linear expansivity of the material = 2.0 x 10-5K-1
-
A.
0.20m -
B.
0.22m -
C.
0.25m -
D.
0.02m
Correct Answer: Option D
Explanation
Safety gap = expansion of the rod
= (alpha times L_0 times Delta t)
where (alpha) = linear expansivity of the material
(L_0) = Initial length of the material
(Delta t) = Change in temperature
(therefore) The safety gap = (2 times 10^{-5} times 20 times (75 – 25))
= (2 times 10^{-5} times 10^3)
= (2 times 10^{-2} m)
= 0.02 m