What is internal energy defined as?

Internal energy is defined as the sum of the kinetic and potential energies of all particles in a system. This encompasses all forms of energy at the microscopic level, including the energy due to thermal motion (kinetic energy) and the energy associated with the positions of particles relative to one another (potential energy).

In terms of kinetic energy, this refers to the energy of particles moving around, which contributes to the temperature of the system. For potential energy, it considers the interactions between particles, such as molecular attractions and repulsions. The internal energy comprises all these contributions and is crucial for understanding how a system will behave under various thermodynamic processes, like heating, cooling, or changing states.

The other options focus on specific forms of energy or processes and do not encompass the complete definition of internal energy. For example, the total energy of macroscopic movements pertains only to bulk motions and neglects individual particle contributions. The energy stored in chemical bonds specifically refers to potential energy related to molecular interactions without considering the kinetic component. Similarly, the energy produced by electrical currents relates to macro-scale energy phenomena, which do not capture the intimate details of particle energy states that define internal energy.