Physics > Work

Explore work in thermodynamics: definition of thermodynamic work, heat and work, features of the internal energy of the body, work in a closed system, formula.

Work, carried out in a closed system, represents the energy transferred to another system, measured by mechanical constraints.

Learning challenge

  • Consider the need to eliminate energy transported between the system as heat from mechanical work.

Key points

  • Thermodynamic work is a mechanical work concept.
  • The body is a change in energy in a closed system, different from the transfer of work.
  • Working in thermodynamics is an organized process where macroscopic forces are involved that affect distances.


  • Heat is energy transported between bodies through thermal contact.
  • Thermodynamics is the section related to heat and the relationship to energy and work.
  • Internal energy is the sum of all energy in the system, including kinetic and potential.


In thermodynamics, work performed in a closed system is energy transported to another system. Measured through mechanical constraints on the system. Thermodynamic works include mechanical (gas expansion) and electrical ones. It necessarily excludes the energy sent between systems in the form of heat. Within a closed system, energy, which differs from the transfer of work, acts as heat.

Gas expansion needs heat transfer during decomposition to maintain a stable pressure. If the pressure does not change, then work is carried out – PΔV

Warmth and work

Transporting heat (Q) and doing work (W) are the daily methods of entering and extracting energy into the system. These processes are fundamentally different. The less organized is heat transfer, which operates on temperature differences. On the contrary, the work has a clear structure and includes a macroscopic force that affects the distance. However, both can offer the same result and increase the temperature mark.

For example, the sun transfers heat when it heats the air in a bicycle tire. It can raise the temperature, so it works in the system. When the temperature gets higher, it is no longer possible to calculate whether this was done by heat transfer or work.

This uncertainty is extremely important. Heat transfer and work – energy in transit. Both are capable of changing the internal energy in the system (completely different from heat or work).

Physics Section

  • Work
  • Zero Law
The first law of thermodynamics
  • The first law of thermodynamics
  • Constant pressure and volume
  • Isothermal processes
  • Adiabatic processes
  • Human metabolism
The second law of thermodynamics
  • The second law of thermodynamics
  • Heat engines
  • Carnot cycles
  • Heat pumps and refrigerators
  • What is entropy?
  • Subtle interpretation of entropy
  • From order to disorder
  • Heat death
  • Living systems and evolution
  • Re-global warming
  • Thermal pollution
The third law of thermodynamics
  • The third law of thermodynamics
  • Adiabatic processes

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