Why Is the Earth Pin of An Electric Plug Longer Than the Other Two Pins?

 

The Function of Earth Pin:

 A 3-pin plug has a live, neutral, and earth pin. The live and neutral pins have the same thickness and length. But the earth pin is a little longer and thicker.

In a properly earthed system, when we connect the 3-pin plug to a 3-pinhole socket, the metallic part of the appliance gets a direct connection to the earth via the earth pin. When there is a current leakage, the earth pin helps to divert the leakage current from the appliance to the ground. Thus, we can avoid electrocution by touching the metallic part. 

Modern sockets possess a safety shuttle in the earth pinhole. When we push the earth pin down, the safety shuttle for the live and neutral pinholes will open.

 

Three Pin Plug

Significant factors:

 

• The earth pin is useless if the building is not earthed.
• The earth pin helps to connect appliances to the ground.
• It helps to open the safety shuttle of modern sockets for the live and neutral pinholes of the socket.

 Why is the Earth Pin of a 3-pin plug larger in diameter?

 The main reason for building the earth pin thick is to avoid the insertion of the earth pin in the wrong pinhole of a socket. The earth pin of a 3-pin plug is longer than the rest of the pins, and the pinhole of a socket for the earth pin is bigger than the other holes. This is to prevent the possibility of inserting the earth pin into a live or neutral pinhole of a socket.

If a conductor has a high cross-sectional area, its conductivity will increase. The leakage current will easily flow to the ground. According to the law of resistance,

R = ρL/A

Where ρ - Resistivity of the conductor, R - Resistance of the conductor, L - Length of the conductor, and A - Cross-sectional area of the conductor.

Why the Earth Pin of a 3-Pin Plug is Longer?

The earth pin of a 3-pin plug is longer than the other pins because it allows the earth pin to connect to the socket first and disconnect last. 

When the earth pin connects to the socket before the neutral and live pins, it allows the metallic part of the appliance to come in contact with the earth first before the live terminal of the plug connects to the socket. 

• Safe working with electrical appliances.
• Another reason is that it helps to push the safety shuttles of sockets to open. 

 The advantages of a thick and long earth pin:

• The thick earth pin prevents the possibility of inserting the earth pin into the wrong pinhole of the socket.
• Leakage current from an appliance would easily pass through the pin to the ground.
• It ensures that the earth pin connects to a socket first and disconnects last.
• This helps to push the safety shuttles of sockets to open.

Why are some home appliances equipped with two-pin plugs while others are provided with three?

 The design of electronic home appliances will not endanger the person operating them if there is any fault or insulation failure within the appliance. Such devices do not require to earth their body because of proper insulation. These devices are with two-pin plugs. However, appliances with metal bodies always require a three-pin plug.

Two Pin Plug

 

 AC power plugs and sockets

AC power plugs and sockets connect devices to mains electricity to supply them with electrical power. A plug is a connector attached to an electrically operated device, often via a cable. Place the socket on the internal walls of buildings and connect it to an AC electrical circuit. Inserting the plug into the socket allows the device to draw power from this circuit.

Plugs and wall-mounted sockets for portable appliances became available in the 1880s to replace connections to light sockets. This type of socket is for convenience and protection from electrical injury. Electrical plugs and sockets differ in voltage and current rating, shape, size, and connector type. Different standards of plugs and sockets are available, and many obsolete socket types are still there in older buildings.

Coordination of technical standards has allowed some plugs to be used across large regions to facilitate the production and import of electrical appliances for travelers. Some multi-standard sockets permit the use of several types of plugs. Incompatible sockets and plugs may be used with the help of adaptors, though these may not always provide safety and performance.[1]

Do you know what AC is?

Alternating current (AC) is an electric current that periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows only in one direction.

Electric power supply to businesses and residences is AC. It is the form of electrical energy that consumers typically use. When we plug kitchen appliances, televisions, fans, and electric lamps into a wall socket, it is consumption of AC. The abbreviations AC and DC are for alternating and direct current, respectively, when they modify current or voltage. [2][3]

The usual waveform of alternating current in electric power circuits is a sine wave, whose positive half-period corresponds with the positive direction of the current and vice versa (a cycle).
In guitar amplifiers, used triangular waves or square waves. Audio and radio signals carried on electrical wires are also examples of alternating current. These alternating currents carry information such as sound (audio) or images (video), sometimes combined by modulation of an AC carrier signal. These currents typically alternate at higher frequencies than those used in power transmission.

Alternating current (green curve). [1]

Overview of connections

Single-phase sockets have two current-carrying connections to the power supply circuit and may also have a third pin for a safety connection to Earth. The plug is a male connector with protruding pins that match the openings and female contacts in the socket. Some plugs also have a female contact, used only for the earth-ground connection. There is no energy supply to any exposed pins or terminals on the socket. In addition to the recessed contacts of the energized socket, plug-and-socket systems often have other safety features to reduce the risk of electric shock or damage to equipment.[1]

Male-Female connectors

In electrical and mechanical trades and manufacturing, the name assigned as male or female connectors is for each half of a pair of mating connectors. [4] The female connector is generally a receptacle that receives and holds the male connector. Alternative terminologies, such as plug and socket or jack, particularly for electrical connectors. [5]
The assignment is a direct analogy with male and female genitalia; the part bearing one or more protrusions fits inside the other is designated male, in contrast to the part containing the corresponding indentations, or fitting outside the other, is designated female. Extension of the analogy results in the verb to mate describing the process of connecting two corresponding parts.

Schematic symbols for male and female connector pins

In some cases (notably electrical power connectors), the gender of connectors is selected according to rigid rules to enforce a sense of one-way directionality (e.g., a flow of power from one device to another). This gender distinction helps to enhance safety and proper functionality by preventing unsafe or non-functional configurations.
In terms of mathematical graph theory, an electrical power distribution network made up of plugs and sockets is a directed tree, with the directionality arrows corresponding to the female-to-male transfer of electrical power through each mated connection.
In other contexts, such as plumbing, one-way flow is not enforced through connector gender assignment. Flows through piping networks can be bidirectional, as in underground water distribution networks, which have designed-in redundancy. 

Socket

Safety

Electrical power outlets are female for safety. In electrical connections where voltage or current is sufficient to cause injury, the part permanently connected to the power source is invariably female, with concealed contacts, to prevent touching of live conductors by people or animals or by conductive items that may cause a short circuit. A male plug, with fully exposed protruding contacts, is installed on the cord of (or directly onto) the device receiving the power. Devices that need to be robust against mechanical damage may use a special male IEC 60320 C14 connector, which is recessed below the surface of a mounting panel, providing the desired physical protection while conforming to safety regulations.

In the case of consumer-level AC power, connector gender is to enforce the safe use of power connectors.

A double-ended male connector for utility-supplied electrical power is dangerous. It has a name, a suicide cable, or a widowmaker cord. [6] Some hardware shops explicitly refuse to make or sell them when asked by customers who have mistakenly hung a string of Christmas lights backward and wish to connect the socket end to a wall socket [7] or who intend to connect a generator or inverter to their home's electrical circuit in the event of a utility power outage. [6] The exposed prongs on the live end of the cable pose electrical shock and fire hazards. When improperly used in a generator setup result, the equipment burns out when utility power is back. [6] It can also backfeed power into the grid, potentially damaging utility equipment or even electrocuting linemen attempting to restore power. [8]

Similarly, an exposed connection on a jumper cable for a 12V automotive battery can be hazardous because of the potentially high current and energy involved. Accidental shorting of the wire to vehicle ground can cause sparks, rapid heating, or even a battery explosion.

In low-voltage use for data communications, electrical shock hazard is not an issue and male or female connectors are used based on other engineering factors such as convenience of use, cost, or ease of manufacturing. [1]

We can select a coaxial power connector so that power from the female plugs into the male jack. Although the plug is female, with a partially recessed center contact, it is still possible for casual, accidental contact with a metallic object to short-circuit the power source. Depending on the design of the power adapter, it may react to a short circuit by shutting down temporarily or instead by blowing out an internal safety fuse.

Common 5.5×2.5 mm coaxial power connectors. Power is provided by the female plug on the right to the male jack on the left; the exposed conductors are not hazardous due to the low voltage. [1]

We can address the potential fire hazard from accidental short-circuiting by the internal safety fuse, although this requires the replacement of a failed power adapter. [1]

Ground and neutral:

In electrical engineering, ground and neutral (earth and neutral) are circuit conductors used in alternating current (AC) electrical systems. The neutral conductor returns the current to the supply. To limit the effects of leakage current from higher-voltage systems- there is a practice of connecting the neutral conductor- to the earth's ground at the point of supply. A ground conductor does not carry current for the operation of the circuit. A ground conductor only carries significant current if there is a circuit fault or shock hazard. Circuit protection devices may detect a fault in a grounded metal enclosure and automatically de-energize the circuit or may provide a warning of a ground fault. [1]

Definitions

Ground or earth in the main (AC power) electrical wiring system is a conductor that provides a low-impedance path to the earth to prevent hazardous voltages from appearing on equipment. In this article, I used the terms ground and earth synonymously. Grounding is also an integral path for home wiring because it causes circuit breakers to trip quickly, which is safer. Adding new grounds requires a qualified electrician with sufficient knowledge of the power distribution region.

A neutral is a circuit conductor that completes the circuit back to the source. NEC states that the connection of the neutral and ground wires should be at the neutral point of the transformer or generator or some system neutral point but not anywhere else. [9] That is for simple single-panel installations. For multiple panels, the situation is more complex. In a polyphase (usually three-phase) AC system, the neutral conductor is intended to have similar voltages to each of the other circuit conductors but may carry very little current if the phases are balanced.[1]

All neutral wires of the same earthed (grounded) electrical system should have the same electrical potential because they are all connected through the system ground. Neutral conductors are usually insulated for the same voltage as the line conductors, with interesting exceptions. [10]

References

1 Wikipedia

2  N. N. Bhargava & D. C. Kulshreshtha (1983). Basic Electronics & Linear Circuits. Tata McGraw-Hill Education. p. 90. ISBN 978-0-07-451965-3.

3^ National Electric Light Association (1915). Electrical meterman's handbook. Trow Press. p. 81.

4 Simon Unwin: Metaphor: an exploration of the metaphorical dimensions and potential of architecture. Routledge 2019, p. 40

.
5^ Huggins, John S. (15 July 2009). "Jack/Plug – Jack, Plug, Male, Female Connectors". An Engineer's Review. Retrieved 1 July 2019.

6 Stanger, Tobie (20 October 2022). "Why 'Suicide' Extension Cords Are So Dangerous". Consumer Reports. Retrieved 17 November 2022.

7^ Marco, Meg (18 March 2009). "Silly: ACE Hardware Is Tired Of People Asking For Double-Ended Male Adapters". consumerist.com. Archived from the original on 2009-03-18. Retrieved 2 November 2021.

8^ https://www.consumerreports.org/home-garden/generators/why-suicide-extension-cords-are-so-dangerous-a1189731437/

 9 https://www.powerandcables.com/wp-content/uploads/2020/01/2008-National-Electrical-Code-NFPA-70.pdf

10^ For example, in North American practice an overhead service-entrance cable has two insulated conductors which are wrapped around and supported by the bare neutral conductor