# Thermodynamics Questions and Answers – Energy

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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Energy”.

1. Energy is a
a) point function
b) property of the system
c) extensive property
d) all of the mentioned

Explanation: Energy has a definite value for every state of the system.

2. The specific energy, e=E/m is an extensive property.
a) true
b) false

Explanation: The specific energy is an intensive property.

3. (m*V*V)/2 gives the
a) macroscopic kinetic energy
b) microscopic kinetic energy
c) macroscopic potential energy
d) microscopic potential energy

Explanation: The formula gives the macroscopic kinetic energy of the fluid element by virtue of its motion.

4. (m*g*z) gives the
a) macroscopic kinetic energy
b) microscopic kinetic energy
c) macroscopic potential energy
d) microscopic potential energy

Explanation: The above formula gives the macroscopic potential energy of the fluid element by virtue of its position.

5. Which of the following types of energy can be present in molecules?
a) translational and rotational kinetic energy
b) electronic energy and vibrational energy
c) chemical energy and nuclear energy
d) all of the mentioned

Explanation: The molecules may be subjected to rotation as well as vibration due to a collision.

6. The total internal energy of the system is given by
a) U=N/ɛ
b) U=Nɛ
c) U=ɛ/N
d) none of the mentioned

Explanation: U=Nɛ where N is the total number of molecules in the system and ɛ represents the energy of one molecule.

7. In an ideal gas there are no intermolecular forces of attraction and repulsion, and the internal energy is a function of temperature only.
a) true
b) false

Explanation: For an ideal gas U depends only on T.

8. Which of the following is true in regard to the energy of an isolated system?
a) dQ≠0
b) dW≠0
c) E=constant
d) all of the mentioned

Explanation: For an isolated system, dQ=dW=0 and hence, dE=0 by first law.

9. A perpetual motion machine of first kind
a) is a fictitious machine
b) can supply mechanical work without dissipating energy
c) violates first law
d) all of the mentioned

Explanation: There cannot be any machine which would continuously supply mechanical energy without other form of energy being dissipated.

10. The limitation of the first law is
a) does not indicate the possibility of a spontaneous process proceeding in a definite direction
b) it assigns a quality to different forms of energy
c) indicates the direction of any spontaneous process
d) none of the mentioned 