Heat, Engines & Entropy Explained | Chapter 20 of University Physics
Heat, Engines & Entropy Explained | Chapter 20 of University Physics Chapter 20 introduces the Second Law of Thermodynamics and explores how it determines the direction of natural processes. You’ll learn the difference between reversible and irreversible processes, how heat engines and refrigerators operate, and why entropy—a measure of disorder—always increases in real systems. Watch the full video summary here for step-by-step explanations and examples. Reversible vs Irreversible Processes Reversible processes are ideal, quasi-static, and maintain equilibrium at each step. In contrast, irreversible processes —such as spontaneous heat flow, friction, and free expansion—occur in one direction and generate entropy. Real-world systems are inherently irreversible, highlighting the fundamental “arrow of time.” Heat Engines Heat engines convert thermal energy into mechanical work by absorbing heat Q H from a hot reservoir, doing work W , and releasing residual heat Q C t...