1ª Lei da Termodinâmica
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
ΔU = Q − W
About this calculator
The 1st Law of Thermodynamics calculator solves the equation ΔU = Q − W, relating the change in internal energy (ΔU) of a system to heat exchanged (Q) and work done (W). The formula is fundamental: positive Q means heat added, positive W means work done by the system. Enter any two values to compute the third, useful for students and professionals to quickly verify results.
To use, input two of three parameters: ΔU (internal energy change), Q (heat), or W (work). The tool automatically calculates the missing one, following the physics sign convention (heat absorbed positive, work done by system positive). Ideal for solving thermodynamics problems, checking experimental data consistency, or simulating processes like gas compression and expansion.
Common use cases include analysis of heat engines, refrigeration cycles, and industrial processes. For example, knowing the heat supplied to a gas and the work it does, you can find its internal energy change. Caution: the calculator assumes consistent signs (Q and W positive per convention). Ensure correct sign input to avoid mistakes.
Frequently asked questions
What does positive ΔU mean?
Positive ΔU means the system's internal energy increased, usually because it received more heat than work done.
Can I use this calculator for cyclic processes?
Yes, in a complete cycle ΔU = 0, so Q = W. The calculator can verify this relation.
What is the difference between Q and W in the formula?
Q is heat exchanged with the surroundings; W is work done by the system (positive) or on the system (negative).
Do I need specific units?
The calculator does not convert units; use joules (J) or any consistent unit for all values.
What if I enter inconsistent values?
The calculator simply computes the third value per the equation. Physical consistency depends on the signs you choose.