Cathode - definition
Cathode - definition
Cathode is the electrode through which electric current enters an external electrical system in the form of electrons. Depending on the type of device or electrochemical process, its polarity may vary; however, the common feature of the cathode is that it serves as the site of electron intake. In the conventional current flow model (from positive to negative), the cathode is located at the negative terminal in galvanic cells and at the positive terminal in electrolytic processes.
In electrochemical applications, the cathode is the electrode where reduction reactions occur—meaning that ions or molecules in the electrolyte gain electrons. In a galvanic cell, such as a battery, the cathode receives electrons from the external circuit and participates in the conversion of chemical energy into electrical energy. In contrast, during electrolytic processes such as electroplating, it is the site where metal ions are deposited and toward which positive ions migrate.
In vacuum devices, electron tubes , and cathode-ray tubes, the cathode acts as the source of electrons emitted into a vacuum as a result of high temperature (thermionic emission) or an electric field. These emitted electrons are accelerated toward the anode and used to generate images, amplify signals, or initiate physical phenomena. In semiconductor diodes, the cathode is the terminal to which a negative voltage must be applied to allow current to flow in the forward direction.
The role of the cathode is fundamental in the design of electronic, energy, and chemical systems, and its correct identification and labeling are crucial for proper device operation. Depending on the application, the cathode may be made from materials resistant to the chemical, thermal, and electrical conditions of the operating environment.
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