Physics

A semiconductor is a solid material whose electrical conductivity can be controlled. It does not behave like a metal, where many electrons move freely, and it does not behave like glass, where electrons are mostly locked in place. Its value comes from the middle ground: heat, light, voltage, and carefully added atoms can change how many charge carriers are available. That controllable behavior is why… How Semiconductors Work: The Physics Behind Modern Electronics

A superconductor is a material that can carry direct electric current with no electrical resistance when it is cooled below its own critical temperature. A true superconductor also pushes out weak magnetic fields as it enters that state, a behavior called the Meissner effect.[Source-a] This is why superconductors are not just “very good metals.” They are a different electrical state of matter. The Clear Version… Superconductors: What They Are and Why They Matter

Optics is the study of how light travels, changes direction, forms images, and interacts with materials. The three ideas that explain many everyday optical effects are reflection, refraction, and lenses. Reflection is light bouncing from a surface. Refraction is light changing direction as it passes between materials. A lens uses refraction to spread light apart or bring it together. Visible light is the part of… Optics and Light: Reflection, Refraction, and Lenses

Entropy is a physical quantity that describes how widely energy and matter can be spread among possible microscopic arrangements. In everyday language it is often called disorder, but the sharper idea is energy dispersal plus probability: a high-entropy state can happen in many more microscopic ways than a low-entropy state. This is why warm and cold objects tend to reach the same temperature, gases spread… What Is Entropy? The Science of Disorder and Irreversibility

Kinetic energy is the energy an object has because it is moving, while potential energy is energy tied to position or configuration within a system (like height in a gravitational field or a compressed spring). Both are measured in joules (J), and in many everyday situations they trade places as things speed up, slow down, rise, or fall [a]🔗. A Practical Way to Think About… Kinetic vs. Potential Energy: Definitions and Examples

The states of matter are the main physical forms a substance can take—solid, liquid, gas, and plasma—based on how tightly its particles are held together and how freely they move.[a]🔗 A Clear Way to Think About It Solids keep their shape, liquids keep their volume, gases expand to fill space, and plasma behaves like a gas with charged particles that react strongly to electric and… The States of Matter: Solid, Liquid, Gas, and Plasma

Electromagnetism is the force behind electric charge and magnetism; gravity is the attraction linked to mass and energy and, in modern physics, to the shape of spacetime. Both can reach across huge distances, yet they behave so differently that one builds atoms while the other builds galaxies. A Clear Starting Point Electromagnetism usually dominates at human scales because it can be extremely strong between charged… Electromagnetism vs. Gravity: The Four Fundamental Forces

The speed of light (usually written as c) is the maximum speed at which information, energy, and physical influence can travel through empty space. In modern SI units, it is defined to be exactly 299,792,458 meters per second in a vacuum[a]↗[b]↗. A Clear Starting Point Light feels “instant” at human distances, but physics treats it as a real speed with real consequences. The important part… The Speed of Light: Why Nothing Travels Faster?

Newton’s three laws of motion are three simple rules that connect forces to how objects move: (1) motion doesn’t change unless there is a net force, (2) net force sets the object’s acceleration, and (3) forces always come in equal-and-opposite pairs between interacting objects.[a]↗ A Clear Mental Picture These laws don’t replace common sense; they sharpen it. They explain why a smooth-gliding object keeps going,… Newton’s Three Laws of Motion: Explained with Examples

The four laws of thermodynamics are the basic rules that connect temperature, heat, work, and entropy. They explain why thermometers can agree, why energy accounting always balances, why some changes have a clear “direction,” and why absolute zero is a limit you can approach but not reach in practice.[g]↗ A Clear Starting Point Thermodynamics is about energy moving and energy changing form in systems you… The 4 Laws of Thermodynamics: Definition and Examples