# electrode

> electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte or a vacuum)

**Wikidata**: [Q176140](https://www.wikidata.org/wiki/Q176140)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Electrode)  
**Source**: https://4ort.xyz/entity/electrode

## Summary
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit, such as a semiconductor, an electrolyte, or a vacuum. It serves as a terminal for current to enter or leave the nonmetallic conducting medium.

## Key Facts
- **Definition**: Electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte or a vacuum)
- **Subclass of**: Lead, electrical terminal
- **Component of**: Transistor, vacuum tube, gas-filled tube, electrochemical cell
- **Connects with**: Electrolyte (in electrochemical cells), semiconductor (in semiconductor devices), vacuum (in vacuum tubes)
- **Aliases**: Terminal, electrodes
- **Library of Congress Authority ID**: sh85042110
- **GND ID**: 4014247-4
- **Mesh Descriptor ID**: D004566

## FAQs
### Q: What is an electrode?
A: An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit, such as a semiconductor, electrolyte, or vacuum. It acts as an interface between metallic and nonmetallic parts of an electrical circuit.

### Q: What is the difference between an anode and a cathode?
A: An anode is an electrode through which conventional current flows into a polarized electrical device, while a cathode is the electrode from which conventional current leaves a polarized electrical device.

### Q: What are electrodes used for?
A: Electrodes are used to establish electrical contact with nonmetallic parts of circuits in devices such as transistors, vacuum tubes, gas-filled tubes, and electrochemical cells. They enable current flow between metallic conductors and nonmetallic media like electrolytes, semiconductors, or vacuum.

### Q: What are some common types of electrodes?
A: Common types include reference electrodes (with stable electrode potential), working electrodes (where electrochemical reactions occur), microelectrodes (used in electrophysiology), ion selective electrodes (sensors for specific ions), and inert electrodes (serve as electron sources/sinks without chemical role).

## Why It Matters
Electrodes are fundamental components in electrical and electrochemical systems, serving as the critical interface between metallic conductors and nonmetallic circuit elements. Without electrodes, it would be impossible to transfer electrical current into and out of electrolytes, semiconductors, or vacuum environments, which are essential in countless modern technologies. In electrochemistry, electrodes enable chemical reactions through electron transfer, powering batteries, fuel cells, and industrial processes. In electronics, electrodes are integral to vacuum tubes, transistors, and semiconductor devices that form the backbone of computing and communications technology. Medical applications rely on specialized electrodes for diagnostics (like measuring oxygen partial pressure with Clark electrodes or CO2 with Severinghaus electrodes) and electrophysiology studies using microelectrodes. The versatility of electrodes across scientific and industrial domains—from lightning protection to sophisticated analytical instrumentation—makes them one of the most widely applied electrical components in existence.

## Notable For
- Serving as the essential interface between metallic conductors and nonmetallic circuit components
- Enabling electrochemical reactions in batteries, fuel cells, and industrial processes
- Being a critical component in vacuum tubes, transistors, and semiconductor devices
- Having diverse specialized forms including reference, working, ion selective, and microelectrodes
- Application across multiple fields: electronics, electrochemistry, medicine, and environmental monitoring

## Body

### Definition and Function
An electrode is an electrical conductor that makes contact with a nonmetallic part of a circuit. The nonmetallic parts can include semiconductors, electrolytes, or vacuum environments. Electrodes are subclassified as a type of lead and electrical terminal.

### Circuit Connections
Electrodes connect with specific nonmetallic components depending on the device type:
- **Electrochemical cells**: Connect with electrolytes
- **Semiconductor devices**: Connect with semiconductors
- **Vacuum tubes**: Connect with vacuum

### Component Relationships
Electrodes are integral parts of:
- Transistors
- Vacuum tubes
- Gas-filled tubes
- Electrochemical cells

### Types and Classifications

#### By Current Flow Direction
- **Anode**: Electrode through which conventional current flows into a polarized electrical device
- **Cathode**: Electrode from which conventional current leaves a polarized electrical device

#### By Electrical Potential
- **Positive electrode**: The electrode having the higher electric potential in a device with two electrodes
- **Negative electrode**: The electrode with the lower electrode potential in a device with two electrodes

#### By Function in Electrochemistry
- **Working electrode**: Electrode on which an electrochemical reaction occurs
- **Reference electrode**: Electrode with a stable, well-known electrode potential
- **Auxiliary electrode**: Electrode which supplies/accepts current from the working electrode
- **Indicator electrode**: Electrode that responds to some species in the solution being investigated, with no appreciable change of bulk solution composition during the measurement
- **Inert electrode**: Electrode that serves as a source or sink for electrons and does not play a chemical role in the reaction

#### Specialized Electrodes
- **Microelectrode**: Electrode used in electrophysiology
- **Ion selective electrode**: Sensor that converts the activity of a specific ion dissolved in a solution into an electrical potential
- **Carbon paste electrode**: Special type of electrodes used in electrochemistry
- **Rotating disk electrode**: Type of electrode used in electrochemistry
- **Platinum electrode**: Foil, wire, disc, or mesh electrode made of platinum; the most commonly used metallic working electrode in electrochemistry
- **Liquid metal electrode**: An electrode that uses a liquid metal
- **Transparent electrode**: Electrode with transparent properties
- **Graphite/black carbon electrode**: Electrode made from graphite or black carbon material

#### Vacuum Tube Electrodes
- **Control grid**: Vacuum tube electrode directly controlling the anode current
- **Suppressor grid**: Grid (electrode) in a vacuum tube used to suppress the dynatron effect, which occurs due to secondary emission at the anode
- **Dynode**: An electrode in a vacuum tube that serves as an electron multiplier through secondary emission
- **Plate electrode**: Type of electrode used in vacuum tubes
- **Wehnelt cylinder**: Electrode in the electron gun assembly of some thermionic devices (inception: 1902)
- **Photocathode**: Surface which converts light into electrons via the photoelectric effect

#### Measurement Electrodes
- **Clark electrode**: Electrode measuring the oxygen partial pressure in a solution
- **Severinghaus electrode**: Electrode that measures carbon dioxide
- **Hydrogen electrode**: Platinized platinum electrode saturated by a stream of pure gaseous hydrogen

#### Other Types
- **Lightning rod**: Metal rod or metallic object to protect from lightning
- **Interdigital electrode**: Electrode with interdigital structure

### Related Devices
Electrodes are related to input/output devices:
- **Computer mouse**: Hand-held device used to move a pointer on a computer display (inception: 1963)
- **Computer keyboard**: Device comprising an arrangement of buttons or keys used to input text in computers

### Authority Identifications
- **GND ID**: 4014247-4
- **Library of Congress Authority ID**: sh85042110
- **Mesh Descriptor ID**: D004566 (Mesh Tree Code: E07.305.250)
- **Encyclopædia Britannica Online ID**: science/electrode
- **Dewey Decimal Classification**: 541.3724, 660.29724

### Described by Sources
- Meyers Konversations-Lexikon, 4th edition (1885–1890)
- Great Soviet Encyclopedia (1926–1947)

## References

1. [Source](https://github.com/JohnMarkOckerbloom/ftl/blob/master/data/wikimap)
2. [Nuovo soggettario](https://thes.bncf.firenze.sbn.it/termine.php?id=17867)
3. Nuovo soggettario
4. Freebase Data Dumps. 2013
5. Integrated Authority File
6. BabelNet
7. National Library of Israel
8. KBpedia
9. GF WordNet
10. [OpenAlex](https://docs.openalex.org/download-snapshot/snapshot-data-format)