1. What is Internal Energy?

Internal energy is the total energy contained within a thermodynamic system. It is the energy necessary to create or prepare the system in any given internal state and includes both kinetic and potential energy of the molecules within the system.

2. How Does the Calculator Work?

The calculator uses the internal energy formula:

Where:

• \( U \) — Internal Energy (Joule)
• \( H \) — Enthalpy (Joule)
• \( P \) — Pressure (Pascal)
• \( V \) — Volume (Cubic Meter)

Explanation: This formula calculates the internal energy of a system by subtracting the product of pressure and volume from the system's enthalpy.

3. Importance of Internal Energy Calculation

Details: Calculating internal energy is crucial for understanding the energy state of thermodynamic systems, analyzing energy transfers, and solving problems in thermodynamics and engineering applications.

4. Using the Calculator

Tips: Enter enthalpy in joules, pressure in pascals, and volume in cubic meters. All values must be valid non-negative numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the relationship between internal energy and enthalpy?
A: Enthalpy (H) is defined as the sum of internal energy (U) and the product of pressure and volume (P×V), hence U = H - P×V.

Q2: Can internal energy be negative?
A: Yes, internal energy can be negative when the product of pressure and volume exceeds the enthalpy value of the system.

Q3: What are the typical units used for these calculations?
A: The SI units are joules for energy, pascals for pressure, and cubic meters for volume.

Q4: Is this formula applicable to all thermodynamic systems?
A: This formula is generally applicable to closed systems where the only work done is pressure-volume work.

Q5: How does temperature affect internal energy?
A: For ideal gases, internal energy depends only on temperature. For real substances, it also depends on pressure and volume.