[Physics Class Notes] on Electric Arc Pdf for Exam

In the year 1801, a British Chemist and inventor, Sir Humphry Davy, was the first to demonstrate an electrical arc to his co-researchers at the London Royal Society and they insisted on the name, the electrical arc. Basically, these electrical arcs, when uncontained, look like scattered or jagged strikes of lightning. This demonstration was later followed by further studies of the electrical arc, as illustrated by Russian scientist Vasily V. Petrov in 1802. Further advancements on electric arc have given many useful applications, the early electrical arc studies produced many industry important inventions such as arc welders.

Thus, an electric arc is an electronic device in which an electric current is allowed to flow between two points through a conducting gas. The two points are called the electrodes, and they are further termed as cathode and anode depending on polarities of the points i.e., depending on the positive polarity and negative polarity respectively. In this article, we will have a discussion on the electric arc, what is electric arc, and electric arc meaning in detail.

What is Electric Arc?

Now, let us begin with the concept of electric arc. The first and foremost question that arose was what is electric arc? So, technically an electric arc is just a visible plasma discharge between two electrodes that is resulted from electrical current ionizing gasses in the air. Electric arcs even occur in nature in the form of lightning. 

The electrical arcs are just electrical current that is either intentionally or unintentionally discharging itself across a gap between two electrodes via a gas, vapour, or air and expending a relatively low voltage across the conductors. The heat and light radiations produced by these electric arcs are usually intense, and they can be used for specific applications, such as arc welding or spotlight illumination. Whereas, the unintentional arcs can have devastating consequences, such as fires, explosions, shock hazards, and at times severe property damages.

At the same time, if the electric arc procedures are used with proper control, electric arcs can be harnessed and further they can be used industrially for welding, plasma cutting and even for particular types of lighting such as fluorescent lighting where a high voltage ionizes the inert gas within a glass tube, then the flow of current across the ionized gas liberates visible light. 

Anyways, for every harnessed electric arc there is an unwanted and unavoidable arc. For instance, poorly installed or any low-quality electrical switches, electrical circuit breakers and other electrical contact points are easily susceptible to these undesired arcs as due to low-quality connections all contacts are either opened and closed.

Electric Arc Meaning:

An arc can be defined as an electric current flowing between two electrodes through an ionized column of gas. A charged anode and a charged cathode create an intense heat of the welding arc. The negative and positive ions are bounced between each other in the plasma column at an accelerated rate. In welding, the arc not only provides the heat needed to melt the electrode and the base metal but under certain conditions it also supplies the means to transport the molten metal to the work from the tip of the electrode. Several mechanisms for metal transfer exist.

The electric arc flashes can literally happen anywhere there is electrical current flowing. Every electrical panel contains many varieties of circuits, buses, and connections. Arcing usually takes place when an electric circuit becomes overloaded and overheats. The overheating causes damage not only to the circuit breaker but also to its connection to the bus. 

Once an electric circuit is damaged, the circuit breaker can malfunction and continue to let electricity flow between its connection instead of tripping, which may lead to many accidents. A circuit breaker is designed in such a way that it should trip or break the circuit connection and not function until it is reset. However, if a broken circuit breaker continues to allow electricity to flow, arcing becomes a possibility.

Electric Arc Welding:

Electric arc welding is a type of welding process in which an electric arc is used to create heat to melt and join metals. A power supply is made between an electric arc, a consumable or non-consumable electrode, and the base material using either direct (DC) or alternating (AC) currents.

So, how does an electric arc welding process be constructed? Arc welding is a type of fusion welding process which is used to join two or more metals. An electric arc with the help of an AC or DC power supply can create an intense heat of about 6500°F which can melt the metal at the join between two workpieces.

The arc can be created either manually or mechanically guided along the line of the join, while the electrode can either carry the current or conduct the current and melt them into the weld pool to supply filler metal to the join.

As the metals easily react chemically to oxygen and nitrogen within the air when heated to high temperatures by the arc, protective shielding gas or slag is deployed to attenuate the contact of the molten metal with the air. After cooling, the molten metal solidifies to form a metallurgical bond.

The electric arc welding can be done in different types. Further, the electric arc welding process can be categorized into two main different types: 

1. Consumable methods

2. Non-consumable electrode methods.

Let us understand these two methods as follows.

Consumable Electrode Methods:

Consumable electric welding is further classified into many types depending on the type of welding being processed. And they are given by:

• Shielded Metal Arc Welding (SMAW):

SMAW is also known as manual metal arc welding (MMA) or stick welding and is a process where the arc is struck between the metal rod (electrode flux coated) and the workpiece, both the rod and workpiece surface are melted to form a weld pool.  At an equivalent time, melting of the flux coating on the rod will form gas, and slag, which may protect the weld pool from the encompassing atmosphere. It is the perfect process to hitch ferrous and non-ferrous materials with a variety of fabric thicknesses altogether.

• Flux Cored Arc Welding (FCAW):

It is created as an alternate choice to SMAW, FCAW uses a continuously fed consumable flux cored electrode and a continuing voltage power supply, which provides a continuing arc length. This process can use a shielding gas or just the gas created by the flux to provide protection from contamination.

• Submerged Arc Welding (SAW):

It is the most ordinarily used process with a continuously consumable electrode and a blanket of fusible flux which becomes conductive when molten, providing a current path between the part and the electrode. The flux can help in preventing spatter and sparks while suppressing fumes and ultraviolet.

• Electro-Slag Welding (ESW):

It is a vertical process that is used to
weld thick plates ( which is above 25mm) in a single pass. ESW depends on an electric arc to start before a flux addition extinguishes the arc. The flux may melt as the electric wire consumable is fed into the molten pool, which creates a molten slag on top of the pool. The heat generated to melt the wire and plate edges is generated through the molten slag’s resistance while the passage of the electric current. 

Just similar to flash welding, SW joins a nut or the fastener, usually with a flange with nubs that melt to create the join, to another metal piece.

Non-consumable Electrode Methods:

• Tungsten Inert Gas Welding (TIG):

It is also known as Gas Tungsten Arc Welding (GTAW), which uses a non-consumable tungsten electrode to create the arc and inert shielding gas to protect the weld and molten pool against atmospheric contamination. 

• Plasma Arc Welding (PAW):

It is almost similar to TIG welding, PAW uses an electric arc between a non-consumable electrode and an anode, which are placed within the body of the torch. The electric arc is used to ionize the gas in the torch and create the plasma, which is then pushed through a fine borehole in the anode to reach the base plate.

Causes of Electric Arc:

Whenever wiring in an electrical panel can is broken even when it is enclosed and guarded against potential hazards. Possible causes include:

• Wiring that is broken or disconnected during routine maintenance or new installations.

• In insulation covering (usually coated with non-conducting materials), the wire gets damaged and exposed.

• The electrical cabinet is left open or damaged leaving it susceptible to the elements.

• Over-fusing is when too many fuses are located inside of an electrical panel.

• Damaged or faulty equipment or components.

Advantages and Disadvantages Electric Arc:

Let us have a look at a few advantages of an electric arc. The advantages of Arc welding are given below:

• Arc welding has high speed as well as good welding efficiency.

• It includes a simple welding apparatus and is simply moveable.

• Arc welding can form a powerful bond between the welded metals.

• It provides reliable welding quality and offers a superior welding atmosphere.

• The power source of this welding is not costly and the process is quick and consistent process.

• The welder can use ordinary domestic current.

Similarly, few disadvantages of Arc welding are given below:

Did You Know?

• Nearly 5 to 10 electric arc explosions occur in an electric equipment in the U.S. every day.

• Around more than 2000 people are treated annually in burn centres with arc flash injuries.

• An electric arc flash causes numerous deaths each year. The accurate number of deaths due to electric arc flash is not reported well.