Which Law Governs the Behavior of Gases in Thermodynamics?

Understanding how gases behave is a fundamental concept in thermodynamics and mechanical engineering. Many scientific laws describe physical phenomena, but when it comes specifically to gases, only a few are directly relevant. Let’s break down this quiz question and understand the correct answer in a clear and detailed way.

QUIZ Question:

Which law governs the behavior of gases in thermodynamics? 

A) Newton’s Law

B) Boyle’s Law 

C) Ohm’s Law 

D) Hooke’s Law

Correct Answer: B) Boyle’s Law

Boyle’s Law is one of the most important gas laws in thermodynamics. It explains the relationship between pressure and volume of a gas when temperature remains constant. According to this law, the pressure of a gas is inversely proportional to its volume.

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This means:

• When the volume of a gas decreases, its pressure increases.
• When the volume increases, the pressure decreases.

Mathematically, Boyle’s Law is expressed as:

P × V = constant

This law is extremely useful in understanding real-world systems such as compressors, engines, breathing mechanisms, and pneumatic devices. For example, in a piston-cylinder arrangement, when the piston compresses the gas (reducing volume), the pressure inside increases, which is a direct application of Boyle’s Law.

Boyle’s Law specifically governs gas behavior under constant temperature conditions, making it a key principle in thermodynamics. That is why it is the correct answer.

Why Other Options Are Not Suitable:

Let’s analyze why the other options are incorrect and understand their actual applications.

A) Newton’s Law – Incorrect:

Newton’s Laws refer to the laws of motion, not thermodynamics. These laws describe how objects move under the influence of forces.

There are three Newton’s Laws:

1. Law of inertia
2. Law of acceleration (F = ma)
3. Action-reaction principle

While these laws are fundamental in mechanics and dynamics, they do not explain the behavior of gases. They deal with motion, force, and mass rather than pressure, volume, or temperature relationships.

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So, Newton’s Law is not suitable for describing gas behavior.

C) Ohm’s Law – Incorrect:

Ohm’s Law is used in electrical engineering, not thermodynamics. It defines the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit.

The formula is:

V = I × R

This law helps in analyzing electrical circuits and designing electrical systems. It has no connection with gases, pressure, or volume.

Since the question is about gas behavior in thermodynamics, Ohm’s Law is clearly unrelated and therefore incorrect.

D) Hooke’s Law – Incorrect:

Hooke’s Law is associated with elasticity in materials. It states that the deformation of a material is directly proportional to the applied force, as long as the material remains within its elastic limit.

The formula is:

F = k × x

Where:

• F = Force
• k = Spring constant
• x = Extension or compression

Hooke’s Law is mainly used in studying springs, structural materials, and mechanical deformation. It explains how solids behave under force, not gases.

Since it does not involve pressure-volume relationships or thermodynamic properties, it is not suitable for this question.

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Conclusion:

Among all the options, Boyle’s Law is the only one that directly explains the behavior of gases in thermodynamics. It establishes a clear relationship between pressure and volume under constant temperature, which is a core concept in many engineering applications.

The other laws—Newton’s Law, Ohm’s Law, and Hooke’s Law—are important in their respective fields (mechanics, electrical engineering, and material science), but they do not relate to gas behavior.

Understanding these differences not only helps in answering quiz questions correctly but also builds a strong conceptual foundation in engineering principles.