Hint: When a high current flows through the circuit, it may damage elements in the circuit. To avoid this we need to break the circuit to avoid the passage of high current through elements. This can be done by the use of a fuse in series with the circuit elements. According to Joule’s law heat is produced when a current passes through a circuit element. If generated heat is more than it can melt that component.
Complete step by step solution: Several times we hear or read about a building catching fire due to a short circuit. Sometimes, if we switch on equipment in our house, the electrical fuse wire melts, and the electric supply shuts down. Let us discuss the cause briefly. The home electrical connection consists of ‘live’, ‘neutral’, and ‘earth’ wires. The ‘live’ and the ‘neutral’ wires have a potential difference of 220V. The ‘earth’ is connected to the ground. Due to a fault in the equipment or if the plastic coating on the ‘live’ and the ‘neutral’ wires gives way, the two wires come in contact with each other and a large current flows through it producing heat. If any inflammable material (such as wood, cloth, plastic, etc.) Existing around that place it can catch fire. To avoid this the fuse wire is used in series with circuit elements. When a high current passes through the circuit, it produces a large heat across the circuit elements. A fuse should melt and break the circuit before any other circuit element gets damaged. To do so, the fuse should have a low melting point so that it melts quickly. According to Joule’s law more heat is generated if the element has a high resistance. Therefore, the fuse should have high resistance so that a large amount of heat is generated across the fuse wire and it will melt quickly. Many times particularly in the summer season, huge electrical power is used in the evenings due to home lighting, fans, air conditioners, use of electricity in shops, etc. As a result, the excessive current is drawn from the transformer supplying the electricity, and if the capacity of the transformer is insufficient, its fuse wire melts and the supply gets shut down. Such events occur due to overloading.
Note: These days’ miniature circuit breakers (MCB) switches are used in homes. When the current in the circuit suddenly increases this switch opens and current stops. Different types of MCBs are in use. For the entire house, however, the usual fuse wire is used. The prime reasons for excessive current are overloading, short circuit, mismatched loads, or device failure.
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