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# Thermodynamics conceptual questions along with solutions

## Multiple Choice Questions

1. A rod of length L having coefficient of Linear expansion $\alpha$ is lying freely on the floor.it is heated so that temperature changes by $\Delta T$ .Find the longitudinal strain developed in the rod
a. 0
b. ?T
c. -?T
d. none of the above

2.if a is coefficient of Linear expansion,b coefficient of areal expansion,c coefficient 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. Constant pressure of gas
d.None of the above

4.when a solid metallic 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

8. Given below are two statements

Statement I: If heat is added to a system, its temperature must increase
Statement II: If positive work is done by the system in a thermodynamics process, its volume must increase

a. Statement I is true but statement II is false
b. Both the statement I and II are true
c. Both the statement I and II are false
d. Statement I is false but statement II is true

9.In a given process on a ideal gas , dW=0 and dQ < 0, then for the gas

a. the temperature will decrease
b. the volume will increase
c. the pressure will remain constant
d. the temperature will increase

10. Heat is given to an ideal gas in an isothermal process
A. Internal energy of the gas will decrease
B. Internal energy of the gas will increase
C. Internal energy of the gas will not change
D. The gas will do positive work
E. The gas will do negative

Choose the correct answer from the options given below

a. A and E only
b. B and D only
c. C and E only
d. C and D only

11. In which of the following process, convection does not takes place primarily

b. Boiling of water
c. Heating air around a furnace
d. warming of glass of bulb due to filament

12. The thermodynamic process in which internal energy of the system remains constant

a. Isochoric
b. Isothermal
d. Isobaric

13. In thermodynamics , heat and work are

a. Point functions
b. Extensive thermodynamics state variables
c. Path functions
d. Intensive thermodynamics state variable

14. Given below are the two statements
Assertion : if dQ and dW represent the heat supplied and work done on the system respectively, then according to the first law of thermodynamics
dQ= dU – dW
Reason: First law of thermodynamics is based on law of conservation of energy

a. A is correct but R is not correct
b. A is not correct but R is correct
c. Both A and R are correct and R is the correct explanation of A
d. Both A and R are correct but R is not the correct explanation of A

Solutions

1. (a)
There was no restriction for it expansion. So no tensile or compressive force developed. Longitudinal strains happens only when tensile or compressive force developed in the rod. So answer a
2.(c)
3.(d)
4.(c)
5. (a),(b)
6.(b)
7.(a),(c)
Due to thermal expansion, the diameter of the disc as well of the hole will increase. therefore the moment of inertia will increase resulting in a increase in the angular speed.
8. (d)
9. (a)
10. d
11. d
12. b
13. c
14. c

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