katódy

A katódy is the negative electrode of an electrochemical cell or vacuum tube. In an electrochemical context, it is the site where reduction occurs, meaning it is the electrode where electrons are gained by chemical species. In a battery or galvanic cell, the cathode is where the positive terminal is located. In electrolysis, the cathode is where the external power source pushes electrons, causing reduction to happen.

In vacuum tubes, such as cathode ray tubes (CRTs) or thermionic valves, the cathode is a heated element that emits electrons. This emission is typically achieved through thermionic emission, where the heat causes electrons to gain enough energy to escape the surface of the cathode material. These emitted electrons are then controlled by other electrodes within the tube to perform specific functions like amplifying signals or creating images on a screen. The term "katódy" is derived from the Greek words "kata" meaning "down" and "hodos" meaning "way," referring to the path of current away from the electrode. Understanding the role of the katódy is fundamental to comprehending the operation of many electronic devices and electrochemical processes.