Definition

1. Noun:
   • The fundamental principle of physics that the total energy of an isolated system is constant despite internal changes: This law states that energy cannot be created or destroyed in an isolated system; it can only be transformed from one form to another or transferred between parts of the system.

Usage Examples

• Noun:
  • The first law of thermodynamics is a statement of the conservation of energy.
  • When calculating the efficiency of an engine, one must apply the first law of thermodynamics.
  • A common formulation of the first law of thermodynamics is that the change in a system's internal energy is equal to the heat added to the system minus the work done by the system.

Advanced Usage

• "to be consistent with the first law of thermodynamics": to not violate the principle of energy conservation.
  • Any proposed perpetual motion machine must be checked to see if it is consistent with the first law of thermodynamics.
• "an expression of the first law of thermodynamics": a specific mathematical or verbal formulation of the law.
  • The equation ΔU = Q - W is a common mathematical expression of the first law of thermodynamics.

Variants and Related Words

• Law of conservation of energy (noun phrase): A closely related principle, often used synonymously in many contexts, stating that the total energy of an isolated system remains constant.
• Thermodynamics (noun): The branch of physical science that deals with the relations between heat and other forms of energy.
• Internal energy (noun phrase): A key concept in the law, referring to the total energy contained within a system.

Synonyms

• Conservation of energy principle: The principle that energy is conserved.
• Energy conservation law: A law stating that energy is neither created nor destroyed.

Related Phrases

• First law (shortened form, noun phrase): A common abbreviation used in technical contexts where "thermodynamics" is implied.
  • According to the first law, the net energy transfer is zero for that cycle.

Noun

1. the fundamental principle of physics that the total energy of an isolated system is constant despite internal changes