# Thermodynamics Questions and Answers – First Law for a Closed System

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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “First Law for a Closed System”.

1. Energy has different forms which include
a) heat
b) work
c) all of the mentioned
d) none of the mentioned

2. Work input is directly proportional to heat and the constant of proportionality is called
a) joule’s equivalent
b) mechanical equivalent of heat
c) all of the mentioned
d) none of the mentioned

Explanation: True for a closed system undergoing a cycle.

3. The value of constant of proportionality, J, has the value
a) 1
b) 0
c) -1
d) infinity

Explanation: In the S.I. system, both heat and work are measured in the derived unit of energy, the Joule.

4. It was Joule who first established that heat is a form of energy, and thus laid the foundation of the first law of thermodynamics.
a) true
b) false

Explanation: Prior to Joule, heat was considered to be an invisible fluid flowing from a body of higher calorie to a body of lower calorie.

5. Which of the following represents the energy in storage?
a) heat
b) work
c) internal energy
d) none of the mentioned

Explanation: Energy in storage is internal energy or the energy of the system.

6. By first law of thermodynamics,
a) Q=ΔE-W
b) Q=ΔE+W
c) Q=-ΔE-W
d) Q=-ΔE+W

Explanation: Q-W is the net energy stored in system and is called internal energy of system.

7. The expression (ΣW)cycle=(ΣQ)cycle applies only to systems undergoing cycles.
a) true
b) false

Explanation: The above expression holds for a closed cycle.

8. Which of the following is the first law for a closed system undergoing a cycle?
a) ∫dW=∫dQ
b) J∫dW=∫dQ
c) ∫dW=J∫dQ
d) none of the mentioned

Explanation: This is the expression for first law of thermodynamics where ∫ denotes the cyclic integral for the closed path.

9. Which of the following an be considered as the definition of energy?
a) Q=ΔE+W
b) Q-W=ΔE
c) first law of thermodynamics
d) all of the mentioned

Explanation: The first law is a particular formulation of the principle of the conservation of energy.

10. The first law of thermodynamics gives only the change on energy ΔE for the process.
a) true
b) false 