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Introduction

This tutorial provides a step-by-step guide on the first law of thermodynamics, also known as the law of energy conservation. Understanding this principle is crucial for students and professionals in fields like physics, engineering, and chemistry, as it lays the foundation for analyzing energy transfer in various systems.

Step 1: Understand the Basic Concept

• The first law of thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another.

• The mathematical expression of this law is:

  [ \Delta U = Q - W ]

  Where:

  • (\Delta U) is the change in internal energy of the system.
  • (Q) is the heat added to the system.
  • (W) is the work done by the system.

Step 2: Identify System and Surroundings

• Define the system you are studying (the part of the universe you focus on) and the surroundings (everything else).
• Determine whether the system is open, closed, or isolated:
  • Open system: Exchanges both matter and energy with surroundings.
  • Closed system: Exchanges energy but not matter.
  • Isolated system: Does not exchange matter or energy.

Step 3: Analyze Energy Transfers

• Identify how energy is transferred into or out of the system:
  • Heat Transfer (Q): Can occur through conduction, convection, or radiation.
  • Work (W): Can be done on the system (positive work) or by the system (negative work).

Step 4: Apply the First Law

• Use the first law to solve problems involving heat and work:
  • Calculate the change in internal energy using the equation provided in Step 1.
  • Determine whether heat was added or removed and whether work was done on or by the system.

Practical Tips

• Always keep track of the signs of (Q) and (W) to avoid confusion.
• Practice with real-world examples, such as gas expansion or heating processes, to see the first law in action.

Common Pitfalls

• Confusing heat and work: Remember that heat refers to energy transfer due to temperature difference, while work is energy transferred through force.
• Neglecting to define the system clearly, which can lead to incorrect calculations.

Conclusion

The first law of thermodynamics is a fundamental concept that helps us understand energy conservation in physical systems. By clearly defining your system and carefully analyzing energy transfers, you can apply this law effectively. Continue your studies by exploring specific applications of the first law in heat engines or refrigeration systems to deepen your understanding.