Change in Internal Energy Calculator
Calculate the change in internal energy (ΔU) of a thermodynamic system using the first law of thermodynamics. Enter the heat added to the system and the work done by the system below.
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Change in Internal Energy (ΔU):
0
J
Interpretation:
The internal energy of the system has not changed.
The First Law of Thermodynamics
The change in internal energy (ΔU) of a system is calculated using the first law of thermodynamics:
ΔU = Q – W
Where:
- ΔU = Change in internal energy of the system
- Q = Heat added to the system (positive if added, negative if removed)
- W = Work done by the system (positive if done by, negative if done on)
Frequently Asked Questions
What is internal energy in thermodynamics?
Internal energy is the total energy contained within a thermodynamic system. It includes the kinetic energy of molecules (from their motion) and potential energy (from molecular interactions). It doesn’t include the system’s overall kinetic or potential energy relative to its surroundings.
Why is work subtracted in the ΔU equation?
Work is subtracted (W in ΔU = Q – W) because when the system does work on its surroundings, it loses energy. Conversely, if work is done on the system, W would be negative, effectively adding to the internal energy.
What are the units of internal energy?
The SI unit for internal energy is the joule (J). Other common units include calories (cal), kilojoules (kJ), and kilocalories (kcal). 1 cal = 4.184 J, 1 kcal = 4184 J, and 1 kJ = 1000 J.
Can internal energy be negative?
Yes, the change in internal energy (ΔU) can be negative if more energy leaves the system (through work or heat loss) than enters it. This means the system’s internal energy has decreased.