PART 1
1. A rod of length L having coefficent of Linear expansion α is lying freely on the floor.it is heated so that temperature changes by ΔT .Find the longitidunal strain developed in the rod
a. 0
b. αΔT
c. -αΔT
d. none of the above
2.if a is coefficent of Linear expansion,b coefficent of areal expansion,c coefficent of Volume expansion.Which of the following is true
a. b=2a
b. c=3a
c. b=3a
d. a=2b
3.which is of them is not used as the measurable properties in thermometer?
a.Resistance of platinum ire
b.Constant volume of gas
c.Contant pressure of gas
d.None of the above
4.when a solid metalic sphere is heated.the largest percentage increase occurs in its
a.Diameter
b. Surface area
c. Volume
d. density
5.the density of the liquid depends upon
a. Nature of the liquid
b. Temperature of the liquid
c. Volume of the liquid
d. Mass of the liquid
6. A metallic sphere has a cavity of diameter D at its center.If the sphere is heated,the diameter of the . cavity will
a. Decrease
b. Increase
c. Remain unchanged
d. none of the above
7.A metallic circular disc having a circular hole at its center rotates about it axis passing through the center and perpendicular to it plane.when the disc is heated
a. Its speed will decrease
b. Diameter will increase
c. Moment of inertia will increase
d. its speed will increase
Solutions
Please take a look at Parts also
Conceptual Questions Part 2
Conceptual Questions Part 3
Conceptual Questions Part 4
Showing posts with label Thermal expansion. Show all posts
Showing posts with label Thermal expansion. Show all posts
Thursday, 14 February 2008
Friday, 18 January 2008
Problem on Thermal Expansion
Question
A circular hole of diameter 2.00 cm is made in an aluminium plate at 0 ° C .what will be the diameter at 100° C?
α for aluminium = 2.3 * 10-3 / ° C
Solution
A circular hole of diameter 2.00 cm is made in an aluminium plate at 0 ° C .what will be the diameter at 100° C?
α for aluminium = 2.3 * 10-3 / ° C
Solution
Thermal Expansion
- Increase in dimension of body due to increase in temperature is call thermal expansion
- Most of the solid material expand when heated
-Consider a rod of length L then for small change in temperature ΔT,the fractional change in length ΔL/L is directly propertional to ΔT
ΔL/L=αΔT --(2)
or ΔL=αLΔT --(3)
- constant α characterizes the thermal expansion properties of a particulaqr material and it is known as coefficient of linear expansion.
- for materials having no prefential direction,every linear dimension changes according to equation (3) and L could equally well represent the thickness of the rod,side lenght of the square sheet etc
-Normally metals expand more and have high value of α
- Agian consider the intial surface area A of any surface .Now when the temperature of the body is increases by ΔT ,the increase in surface area is given by
ΔA=αAAΔT ----(4)
where αA is the coefficient of area expansion
-Similary we can define coefficient of volume expansion as fractional change in volume ΔV/V of a substance for a temperature change ΔT
as ΔV=αVVΔT ----(5)
- K-1 is the unit of these coefficents expansions
- These three coefficent are not strictly constant for a substance and these value is depends on temperature range in which they are measured.
Relation between volume and linear coefficient of expansion for solid materail: Consider a solid parallopide with dimension L1,L2 and L3
then volume is
V= L1L2L3
when temperature increase by a amount ΔT then each linear dimension changes and then new volume is
V+ΔV=L1L2L3(1+αL )
V+ΔV=V(1+αLΔT)3
V+ΔV=V(1+3αLΔT+3αL2ΔT2+αL3ΔT3)
if ΔT is small the higher order can be neglected.Thus we find
V+ΔV=V(1+3αLΔT)
ΔV=3αLVΔT
Comparing this with equation (5) we find
αV=3αL
- Increase in dimension of body due to increase in temperature is call thermal expansion
- Most of the solid material expand when heated
-Consider a rod of length L then for small change in temperature ΔT,the fractional change in length ΔL/L is directly propertional to ΔT
ΔL/L=αΔT --(2)
or ΔL=αLΔT --(3)
- constant α characterizes the thermal expansion properties of a particulaqr material and it is known as coefficient of linear expansion.
- for materials having no prefential direction,every linear dimension changes according to equation (3) and L could equally well represent the thickness of the rod,side lenght of the square sheet etc
-Normally metals expand more and have high value of α
- Agian consider the intial surface area A of any surface .Now when the temperature of the body is increases by ΔT ,the increase in surface area is given by
ΔA=αAAΔT ----(4)
where αA is the coefficient of area expansion
-Similary we can define coefficient of volume expansion as fractional change in volume ΔV/V of a substance for a temperature change ΔT
as ΔV=αVVΔT ----(5)
- K-1 is the unit of these coefficents expansions
- These three coefficent are not strictly constant for a substance and these value is depends on temperature range in which they are measured.
Relation between volume and linear coefficient of expansion for solid materail: Consider a solid parallopide with dimension L1,L2 and L3
then volume is
V= L1L2L3
when temperature increase by a amount ΔT then each linear dimension changes and then new volume is
V+ΔV=L1L2L3(1+αL )
V+ΔV=V(1+αLΔT)3
V+ΔV=V(1+3αLΔT+3αL2ΔT2+αL3ΔT3)
if ΔT is small the higher order can be neglected.Thus we find
V+ΔV=V(1+3αLΔT)
ΔV=3αLVΔT
Comparing this with equation (5) we find
αV=3αL
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