When we use an electrical socket, we certainly notice that it consists not only of two holes, but also of an additional element – a metal pin. Have you ever wondered what his role is? Why is it put there?
There are many different types of electrical sockets around the world. In Poland, the most common plugs are type E (CEE 7/5), which is also popular in countries such as Belgium, Czech Republic, France and Slovakia. These are sockets consisting of two holes (for the phase and neutral wire) and a metal pin. The presence of this last element is very important, especially from a security standpoint.
How is an electrical socket constructed?
Electrical socket slots have spring-loaded metal connections that connect to the mains wires. When the device plug is inserted into the socket, these contact points fit tightly into the metal pins of the plug. This allows current to flow (from the contacts to the pins). There is a potential difference between these holes, called potential. When the plug is inserted into the socket, due to the non-zero voltage, current flows from one hole (called the phase) to the other (called the neutral or zero) through the device being fed, giving it electrical energy.
The question here is why two holes are needed in the socket? The answer to this question relates to the principle of conservation of electric charge. According to her, the charge cannot be destroyed, so it must accumulate somewhere or flow away.
If there is only one hole in the socket, the electrical charge will flow into and build up on the connected device. As a result, the potential of the device will quickly equalize the potential of the hole, causing current to stop flowing due to lack of voltage.
What is a metal pin for?
But let's go back to the metal pin. Its main function is to protect the user in case of contact with the body of a device with a short circuit with a phase conductor. This condition may occur as a result of puncture or damage to the device body. The absence of a metal pin may result in the user sustaining an injury that is dangerous to his life and health.
“Since the current always flows along the path with the least electrical resistance, and the resistance of the cable is much lower than the resistance of the human body, most of the current will flow through the ground rather than the human body. A large current flow in this path also causes electrical protection” – we read in Summary about the metal pin on the Ask a Physicist page.
The main functions of the pin in the electrical socket are:
- Protection against electric shock: The ground pin is connected to ground, which means that in the event of a fault where the metal casing of the device becomes electrified due to leakage of current, the current will be discharged to ground. This protects people using the device from electric shock.
- Voltage stability: Grounding helps stabilize the voltage in an electrical system, which is especially important in the event of voltage surges or surges, protecting devices from damage.
- Increasing the effectiveness of protection systems: In some systems, grounding works in conjunction with other protective systems, such as residual current devices, which detect irregularities in the current circuit and quickly disconnect the power to prevent further damage or hazards.
The grounding pin is especially important in high-power devices or those placed in damp or humid areas where the risk of shock is higher.
