# cathode

> electrode from which conventional current leaves a polarized electrical device

**Wikidata**: [Q175233](https://www.wikidata.org/wiki/Q175233)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Cathode)  
**Source**: https://4ort.xyz/entity/cathode

## Summary
A cathode is an electrode from which conventional current leaves a polarized electrical device. It serves as a crucial component in various electrical and electronic devices, including batteries, vacuum tubes, and diodes. The cathode is the opposite of an anode in an electrical system.

## Key Facts
- A cathode is defined as an electrode from which conventional current leaves a polarized electrical device
- Cathodes are classified as a type of electrode, which is an electrical conductor used to make contact with nonmetallic parts of a circuit
- The cathode is the opposite of an anode in electrical systems
- Cathodes have three main subclasses: sulfur cathode, cold cathode, and hot cathode
- Cathodes are integral components in vacuum tubes, gas-discharge lamps, diodes, silicon controlled rectifiers, thyristors, light-emitting diodes, and batteries
- The cathode is assigned IUPAC Gold Book ID: C00905
- The Dewey Decimal Classification for cathodes is 660.29724 and 541.3724
- The Library of Congress Authority ID for cathode is sh85021037
- The cathode has a Wikipedia entry with 70 sitelinks across different language versions

## FAQs
### Q: What is the function of a cathode in an electrical device?
A: A cathode is the electrode from which conventional current leaves a polarized electrical device. In many devices, it's also the site where reduction reactions occur, making it essential for the proper functioning of batteries, diodes, and other electronic components.

### Q: How does a cathode differ from an anode?
A: A cathode is the electrode from which conventional current leaves a device, while an anode is where conventional current enters. In electrochemical terms, reduction occurs at the cathode, while oxidation occurs at the anode.

### Q: What are the different types of cathodes?
A: Cathodes are categorized into several types, including sulfur cathodes, cold cathodes, and hot cathodes. Cold cathodes are used in fluorescent lamps, while hot cathodes are heated to emit electrons, commonly found in vacuum tubes.

### Q: Where are cathodes commonly used?
A: Cathodes are essential components in vacuum tubes, gas-discharge lamps, diodes, silicon controlled rectifiers, thyristors, light-emitting diodes, and batteries. They serve as crucial electrodes in various electronic and electrochemical devices.

## Why It Matters
Cathodes are fundamental components in modern electrical and electronic systems, playing a critical role in the operation of countless devices we use daily. From enabling energy storage in batteries to facilitating electron emission in vacuum tubes and LED displays, cathodes serve as essential interfaces between electrical circuits and various materials. The development of different cathode types has been instrumental in advancing technologies from early telecommunications to modern renewable energy storage. In batteries, cathode materials determine energy density, charge rates, and longevity, directly impacting the performance of electric vehicles and portable electronics. The ongoing research into novel cathode materials continues to drive improvements in energy efficiency and sustainability across multiple industries. Without cathodes, the fundamental processes of electrical conduction and electrochemical reactions that power our technological world would not be possible.

## Notable For
- The cathode is universally defined as the electrode from which conventional current leaves a polarized electrical device, providing a consistent reference point across all electrical systems
- Cathodes have evolved into specialized forms including sulfur cathodes for battery technology and temperature-specific variants (hot and cold) for different applications
- The IUPAC Gold Book has assigned a standardized identifier (C00905) to cathodes, reflecting their established importance in electrochemical terminology
- Cathodes are integral components in both historical technologies like vacuum tubes and modern innovations such as light-emitting diodes and silicon-controlled rectifiers

## Body
### Definition and Function
A cathode is specifically defined as an electrode from which conventional current leaves a polarized electrical device. In electrochemical terms, cathodes are where reduction reactions occur, gaining electrons during the process. This fundamental characteristic distinguishes cathodes from anodes, which are the electrodes where conventional current enters and where oxidation reactions take place.

### Classification and Types
Cathodes belong to the broader class of electrodes, which are electrical conductors used to make contact with nonmetallic parts of a circuit. The cathode category includes several specialized subclasses:
- Sulfur cathode: A specific material used in certain battery technologies
- Cold cathode: A type of electrode that operates at room temperature and is commonly found in cold cathode fluorescent lamps
- Hot cathode: An electrode that requires heating to function, typically used in vacuum tubes and other electron-emitting devices

### Applications in Electrical Devices
Cathodes serve as essential components in a wide variety of electrical and electronic devices:
- Vacuum tubes: Where they emit electrons
- Gas-discharge lamps: Including fluorescent and neon lights
- Diodes: Essential for one-way electrical current
- Silicon controlled rectifiers: Used in power control applications
- Thyristors: Semiconductor devices used for switching and control
- Light-emitting diodes (LEDs): Where cathodes help produce light
- Batteries: Where they serve as one of the two electrodes for electrochemical reactions

### Standardization and Identification
The cathode concept has been formally standardized across various knowledge systems:
- IUPAC Gold Book ID: C00905
- Dewey Decimal Classification: 660.29724 and 541.3724
- Library of Congress Authority ID: sh85021037
- GND ID: 4163451-2
- Lex ID: katode

These identifiers ensure consistent reference to cathodes across scientific literature and educational resources.

### Cross-Linguistic References
The concept of cathode is recognized across multiple languages and reference works:
- English: Cathode, catodo
- French: électrode négative
- German: Katode
- Spanish: polo negativo, catodo
- Arabic: الكاثود, كاثود, مهبط كهربائي
- Chinese: 陰極, 还原极
- Italian: catodo, càtodo

The widespread recognition of cathodes across languages underscores their fundamental importance in electrical engineering and physics.

## References

1. Nuovo soggettario
2. Freebase Data Dumps. 2013
3. Integrated Authority File
4. BabelNet
5. Quora
6. National Library of Israel Names and Subjects Authority File
7. [OpenAlex](https://docs.openalex.org/download-snapshot/snapshot-data-format)