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Fuses: Application Field and Working Principle

A fuse is a protective device that is specifically designed to protect circuits and components in electrical devices from overloads and short circuits. Fuses are rated for their capability to carry a specific amount of current and are categorized accordingly. Depending upon the magnitude of current, these fuses are classified as low current, medium current, and high current fuses. It is essential to understand the application field and working principle of each type of the fuse.

Low Current Fuses
Low current fuses are used to protect electrical gadgets such as televisions, refrigerators, microwaves, and other electronic devices. These fuses are rated to carry up to 200 mA current and can be used to protect low-power circuits. These fuses consist of a small strip of metal that melts when too much current flows through it. The metal strip has thinner sections that are designed to melt first when the current level rises above the designed limit.

Medium Current Fuses
Medium current fuses protect circuits that are designed to bear up to 10 A. Appliances like heaters, geysers, indoor lights, and street lamps are some examples of medium current fuses. These fuses are made from a metal wire that is enclosed in a cylindrical plastic body. Fuses are required to be durable, so they are made of heavy-duty materials. When the current flow through the fuse exceeds the rated current limit, the metal wire inside the cylindrical plastic body melts and the fuse gets tripped, thus breaking the circuit.

High Current Fuses
High current fuses are designed to bear currents that exceed 10 A. These fuses are used to protect high load appliances such as motors, transformers, and air-conditioners. High current fuses consist of a metal strip that is enclosed in a glass body. When the current crosses the designed limit, the metal strip dissipates its heat and melts. This breaks the circuit and the current gets interrupted. High current fuses are made of materials such as copper, silver alloy, and metal oxide that can bear the high current.

Working Principle
The working principle of a fuse is based on the heating action of the current passing through it. As we know, when an electrical current passes through a conductor, its resistance causes the electrical energy to be converted into heat energy. The heat energy thus produced is more present in current carrying conductor than in the surrounding. When the heat energy exceeds the melting point of the conductor, it melts and the current is interrupted. This prevents the material surrounding the conductor from burning out, thereby protecting the circuit from any further damage.

In conclusion, fuses are designed for the purpose of protecting circuits and components from overloads and short circuits. Fuses are rated for their capability to carry a specific amount of current and are categorized accordingly as low current, medium current, and high current fuses. Since fuses are designed to be tough and durable, they are made of heavy-duty materials that can bear the specified amount of current. The working principle of a fuse is based on the heating action of the current passing through it which melts the material of the fuse and breaks the circuit.

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