Physicists know that electrons in a solid are always moving based on experimental observations and the understanding of quantum mechanics. Quantum mechanics is the branch of physics that describes the behavior of particles at the atomic and subatomic levels.
According to quantum mechanics, electrons in a solid occupy specific energy levels or bands. These energy levels can be thought of as allowed states for the electrons to occupy. Within these energy levels, the electrons have a range of possible velocities and positions.
Experimental evidence, such as the observation of electric current and thermal conductivity in solids, provides strong support for the notion that electrons in solids are constantly in motion. Here are a few key points that help illustrate this concept:
Electrical conductivity: Solids can conduct electricity because the electrons in the material can move in response to an applied electric field. This movement of electrons constitutes an electric current. Conductivity experiments and electrical measurements demonstrate that electrons can flow through the solid, indicating their motion.
Heat conduction: The thermal conductivity of a solid is related to the movement of electrons. As electrons gain thermal energy, they move more vigorously and transfer this energy to neighboring electrons, thereby conducting heat. The efficiency of heat transfer in solids confirms the mobility of electrons.
Scattering experiments: Experiments such as electron scattering and diffraction provide direct evidence of electron motion. By firing electrons at a solid sample and observing how they interact and scatter, scientists can infer their velocities and trajectories.
It's important to note that while electrons are in motion, their movements are subject to various factors, such as the presence of an applied electric field, interatomic forces, and electron-electron interactions. Quantum mechanics provides a framework for understanding and predicting the behavior of electrons in solids, taking into account their motion, energy levels, and interactions with other particles.
In summary, physicists have established the understanding that electrons in solids are in constant motion through experimental observations and the application of quantum mechanics. The principles of quantum mechanics provide a theoretical framework that explains and predicts the behavior of electrons in solids.