First Law of Thermodynamics Explained
The first law of thermodynamics is a core principle governing energy transfer and transformation within physical systems.
Principle of Conservation
This law fundamentally states that energy in an isolated system remains constant over time. It cannot be created or destroyed, only changed from one form to another.
- Energy Conversion: The law highlights that energy can be converted between different forms, such as heat, work, and internal energy.
- System Energy: For any process, the change in the internal energy of a system ($\Delta U$) is equal to the heat added to the system ($Q$) minus the work done by the system ($W$). The mathematical expression is:
$\Delta U = Q - W$
Relation to Conservation Laws
The first law of thermodynamics is essentially an expression of the conservation of energy applied to thermodynamic processes.
Other conservation laws, like the conservation of mass or momentum, are fundamental but are described by different physical laws (e.g., Newton's laws for momentum, principles of mass continuity for mass). The increase in entropy relates to the second law of thermodynamics, not the first.
Important Questions from Thermodynamics
A system that does NOT allow exchange of heat with its surrounding is called
A system that does NOT allow exchange of heat with its surrounding is called
- Which of the following statements correctly describes the thermodynamic classification of entropy?
- A mass of $10 \text{ kg}$ is suspended vertically by a rope from the roof. A horizontal force is applied on the rope at a point $P$. The point $P$ is $1 \text{ m}$ vertically below the roof attachment point, and the length of the rope segment from the roof to $P$ is $2 \text{ m}$. If the suspended mass is in equilibrium, what is the tension in the upper part of the rope (from roof to $P$)? (Take $g = 10 \text{ ms}^{-2}$)
Example of thermoplastic among the following is
