Thermodynamics Questions and Answers Part-11

1. The specific heat of a substance at constant volume is defined as the rate of change of ___ with respect to ___
a) specific internal energy, temperature
b) work, pressure
c) specific internal energy, pressure
d) heat, temperature

Answer: a
Explanation: cv=∂u/∂T at constant volume.

2. Specific heat of a substance at constant volume is a property of the system.
a) true
b) false

Answer: a
Explanation: Since T,v and u are the properties of the system, specific heat at a constant volume is a property of the system.

3. Heat transferred at constant _____ increases the _____ of a system.
a) pressure, increases
b) volume, increases
c) both of the mentioned
d) none of the mentioned

Answer: c
Explanation: At constant pressure, (dQ)=dh and at constant volume, Q=Δu

4. The specific heat of a substance at constant pressure is defined as the rate of change of ___ with respect to ___
a) work, pressure
b) enthalpy, temperature
c) enthalpy, pressure
d) heat, temperature

Answer: b
Explanation: cp=∂h/∂T at constant pressure.

5. The heat capacity at constant pressure Cp
a) m/cp
b) cp/m
c) mcp
d) none of the mentioned

Answer: c
Explanation: Cp=(mass*specific heat at constant pressure).

6. Specific heat of a substance at constant pressure is a property of the system
a) true
b) false

Answer: a
Explanation: cp is a property of a substance just like cv.

7. When there is mass transfer across the system boundary, the system is called
a) isolated system
b) closed system
c) open system
d) none of the mentioned

Answer: c
Explanation: Basic definition of an open system.

8. If a certain mass of steam is considered as the thermodynamic system, then the energy equation becomes
a) Q=ΔKE + ΔPE – ΔU + W
b) Q=ΔKE + ΔPE – ΔU – W
c) Q=-ΔKE – ΔPE + ΔU + W
d) Q=ΔKE + ΔPE + ΔU + W

Answer: d
Explanation: Q=ΔE + W and E=KE + PE + U.

9. The surface of the control volume is known as the control surface.
a) true
b) false

Answer: a
Explanation: This is same as the system boundary of the open system

10. Steady flow means that the rates of flow of mass and energy across the control surface
a) varies
b) remains constant
c) depends on the control surface
d) none of the mentioned

Answer: b
Explanation: In a steady flow rate of flow remains constant.