Trystan Casey
An electric arc is a device where an electric current flows between two points called electrodes. The electric arc is the visible plasma between the two electrodes that is caused when the electrical current ionizes gases. Electric arcs can be used in welding, lighting, and plasma cutting. They can also be dangerous when not intended, causing personal injury, death, fire, equipment damage, and property loss.
| Characteristics | Values |
|---|---|
| Definition | An electric arc is an electrical breakdown of a gas that produces a prolonged electrical discharge. |
| Discovery | Sir Humphry Davy discovered the short-pulse electric arc in 1800 and named it in 1801. |
| Visual Appearance | The visible plasma between two electrodes. |
| Colour | Electric arcs can be of different colours depending on the type of material used. |
| Temperature | Electric arcs can produce temperatures up to 20,000°C. |
| Uses | Electric arcs have many uses, including welding, lighting, plasma cutting, arc furnaces, steel recycling, and manufacturing processes. |
| Hazards | Electric arcs can be dangerous, causing burns, fires, explosions, and electric shocks. They are a major threat to worker safety and can cause damage to property. |
| Safety Measures | To prevent injuries, workers should use appropriate personal protective equipment (PPE) and companies should provide arc flash-rated products like gloves. |
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What You'll Learn
- Electric arcs are a form of electric discharge with high current density
- They can be used for welding, lighting, and plasma cutting
- They can also be dangerous, causing burns, fires, and explosions
- In the late 19th century, they were widely used for public lighting
- They are characterised by visible light emission, high current density, and high temperature
Electric arcs are a form of electric discharge with high current density
An electric arc is a device where an electric current flows between two points called electrodes. The electric arc is the visible plasma between the two electrodes that is caused when the electrical current ionizes gases. Electric arcs can be used in welding, lighting, and plasma cutting. The term "electric arc" refers to both the electric current and the electrodes between which it travels.
The maximum current through an arc is limited only by the external circuit, not by the arc itself. An arc between two electrodes can be initiated by ionization and glow discharge, when the current through the electrodes is increased. The breakdown voltage of the electrode gap is a combined function of the pressure, distance between electrodes, and type of gas surrounding the electrodes.
When an arc starts, its terminal voltage is much lower than a glow discharge, and the current is higher. An arc in gases near atmospheric pressure is characterized by visible light emission, high current density, and high temperature. A drawn arc can be initiated by two electrodes initially in contact and then drawn apart, which can form an arc without the high-voltage glow discharge. This is how a welder starts to weld a joint.
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They can be used for welding, lighting, and plasma cutting
Electric arcs have a variety of applications, including in welding, lighting, and plasma cutting.
Welding
Arc welding is a process that uses electricity to generate enough heat to melt metal. The process involves creating an electric arc between a metal stick (or "electrode") and the base material, melting the metals at the point of contact. When the melted metals cool, they result in a joining of the metals. The arc length is kept constant, and any fluctuation in the distance between the wire and the base material is quickly rectified by a change in current. The voltage is directly related to the length of the arc, and the current is related to the amount of heat input.
Lighting
Electric arcs can also be used for lighting. In the late 19th century, carbon arc lights were used for street lights and searchlights. Electric arcs were also in wide use for public lighting. Today, electric arcs are used in fluorescent tubes, mercury, sodium, and metal halide lamps for lighting, and in xenon arc lamps for movie projectors and theatrical spotlights.
Plasma Cutting
Plasma arc cutting is based on the establishment of a direct current arc between a tungsten electrode and the surface of a conducting metal. The arc is created by ionizing a gas (plasma gas) and then blowing the ionized plasma towards the surface of the workpiece, creating a conductive pathway for the plasma current. The heat generated by the impingement of the arc on the workpiece causes local melting, and the force created by the velocity of the plasma gas stream blows the molten metal away, creating a cut.
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They can also be dangerous, causing burns, fires, and explosions
Electric arcs can be extremely dangerous, causing burns, fires, and explosions. They can also lead to equipment damage and property loss. In fact, one of the greatest threats to worker safety is electrical arcs. Unwanted arcs in electrical circuits can cause fires and explosions. These arcs can be caused by damaged wiring or overloaded circuits. The high temperatures produced by electric arcs, which can reach up to 20,000°C, make them a significant hazard.
To ensure workplace safety, it is crucial to implement preventive measures and safety protocols. This includes providing workers with appropriate personal protective equipment (PPE), such as gloves, helmets, goggles, and flame-resistant clothing. Additionally, companies should offer educational resources, such as arc flash video training, to keep staff informed about the dangers of working in energized environments and how to protect themselves.
The risk of electrical arcs can be mitigated by addressing potential issues in the external circuit, as the maximum current in an arc is limited by it. Techniques for arc suppression can also be employed to reduce the likelihood and duration of arc formation.
It is important to note that electrical arcs can occur not only in industrial settings but also in residential and commercial buildings. Therefore, it is essential for everyone to have a basic understanding of electrical arcs and take necessary precautions to minimize potential hazards.
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In the late 19th century, they were widely used for public lighting
An electric arc is a device where an electric current flows between two points called electrodes. The electric arc is the visible plasma between the two electrodes that is caused when the electrical current ionizes gases. In the late 19th century, electric arc lighting was widely used for public lighting.
The concept of carbon-arc lighting was first demonstrated by Humphry Davy in the early 19th century. Davy used charcoal sticks and a two-thousand-cell battery to create an arc across a 4-inch gap. He mounted his electrodes horizontally and observed that, due to the strong convection flow of air, the arc formed the shape of an arch. This led to the term "arch lamp", later contracted to "arc lamp" when the devices became commonly used.
In the 1870s, arc lamps began to be more commonly seen, with the Yablochkov candle being one of the first examples. On April 29, 1879, Public Square in Cleveland, Ohio, was illuminated by one of these lamps, and Wabash, Indiana, claims to be the first city ever to be lit with "Brush Lights" on March 31, 1880. By the 1890s, the Thomson-Houston company was the dominant electrical manufacturing company in the U.S. and played a key role in the expansion of arc-lighting systems.
The tendency of electric arcs to flicker and hiss was a notable problem. In 1895, Hertha Marks Ayrton wrote a series of articles for the Electrician, explaining that these issues were caused by oxygen coming into contact with the carbon rods used to create the arc. Ayrton's work was significant in that she became the first woman to read her own paper before the Institution of Electrical Engineers (IEE) in 1899, and she was elected as the first female member of the IEE shortly thereafter.
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They are characterised by visible light emission, high current density, and high temperature
Electric arcs are characterised by visible light emission, high current density, and high temperature. This is due to the electrical current ionising gases, which produces a plasma that emits light. The colour of the light depends on the type of material used. The temperature of an electric arc can reach up to 20,000°C, which is almost four times hotter than the surface of the sun.
The high temperatures of electric arcs are caused by the resistance along the continuous electric arc, which creates heat and ionises more gas molecules. The degree of ionisation is determined by temperature. Electric arcs are initiated by increasing the current through the electrodes, which can be separated after initial contact to create an arc without a high-voltage glow discharge. This is how welders start to weld a joint.
The first continuous electric arc was discovered in 1802 and described in 1803 by Vasily V. Petrov, a Russian scientist who experimented with a copper-zinc battery. Sir Humphry Davy discovered the short-pulse electric arc in 1800 and named it an "arc" because of its shape when the distance between electrodes is not small. In 1895, Hertha Marks Ayrton wrote about the flickering and hissing of electric arcs, which she attributed to oxygen coming into contact with the carbon rods used to create them.
Electric arcs have many practical applications, such as in welding, lighting, and plasma cutting. They can be used in camera flashes, spotlights, and fluorescent lighting. However, they can also be dangerous, causing burns, fires, explosions, and electric shocks. In the workplace, they are considered one of the most dangerous events and can cause injury or death. It is important to take electrical arc safety seriously and use appropriate personal protective equipment.
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Frequently asked questions
An electric arc is a device where an electric current flows between two points called electrodes. The electric arc is the visible plasma between the two electrodes that is caused when the electrical current ionizes gases.
Electric arcs produce a significant amount of bright light and high levels of heat. They can have various different colours depending on the type of material from which they are made.
Electric arcs have many practical applications. They can be used in welding, lighting, plasma cutting, and arc furnaces. They can also be used in camera flashes, spotlights, and fluorescent lighting.
An electric arc can be initiated by different methods, such as thermionic emission, field emission, or ionization and
Yes, electric arcs can be extremely dangerous when not intended. They can cause personal injury, death, fires, explosions, equipment damage, and property loss.
