Thermal expansion: solid or liquid expand when heat is applied to them. The expansion of any material both liquid and solid depend on the nature of the substance.
Thermal expansion question and answer 1
Define the followings
(a) Linear expansity os solid can be defined as increase in length per unit length, per unity rise in temperature. It is given as
(b). Cubic or volume expansivity, is defined as the increase in volume of a liquid per a unit volume per unit rise in temperature. It is given as
(c). Superficial of area expansivity is defined as increase in area of a substance per unit area per unit rise in temperature. The formula is also given as
thermal expansion question and answer 2
A brass of length 100m increases to 100.5m, when heated from 50oc to 100oc. Calculate it linear expansivity
But (Ѳ2-Ѳ1) = 100oc – 50oc = 50oc, L1-L2 = 100.5 = 100 = 0.5m, L1 = 100m, and α= ?
Linear expansivity α = 10-4K-1
thermal expansion question and answer 3
An iron rod of linear expansivity 24 x 10-6K-1 and L1 = 60m, expands when heated through 100oc, calculate (a) increase in length and (b) final length.
L1 =60m, Ѳ=100oc, α = 12 x 10-6K-1 and ( L2-L1 )=?
L2-L1 = 12 x10-6 x60 x 100 = 0.072
The increase in length = 0.072m
(b). Final length = increase in length + original length , that is
60 + 0.072 = 60.072m
Thermal expansion question and answer 4
Mercury in glass thermometer has a bulb of volume 0.4cm3 and a tube of 20 x 10-5cm2. Calculate
(a). the apparent increase in volume of the mercury when the temperature rises from 0oc to 100oc
(b). the distance between the fixed points
V2-V1 = γaV1(Ѳ2-Ѳ1) where V1= 0.4cm, (Ѳ2-Ѳ1) = 100oc -0oc = 100oc, γa = 12 x 10-6c-1
V2-V1 = 12 x 10-6 x 0.4 x 100 = 48 x 10-5
Increase in volume = 48 x 10-5cm3
(b). to calculate the distance between fixed point, consider calculating the volume of the tube that is
20 x 10-5cm2 x h = 48 x 10-5
0.00002h = 0.00048
The distance between the fixed point = 2.4cm