Question 1: Define a fuse and explain its primary function in an electrical circuit.

Answer: A fuse is a safety device consisting of a metal wire or strip that melts when excessive current flows, thereby interrupting the circuit and preventing damage or fire. Its primary function is to protect electrical devices and users from overloads and short circuits.

Question 2: Describe how a fuse operates when there is an overload current in the circuit.

Answer: When there is an overload current, the fuse's metal wire heats up due to the excessive current. If the current exceeds the fuse's rated current, the wire melts, breaking the circuit and stopping the flow of electricity.

Question 3: Identify two safety precautions to observe when replacing a blown fuse.

Answer: First, ensure the power supply is turned off before replacing the fuse. Second, use a fuse with the correct rated current and voltage specified for the circuit.

Question 4: Calculate the fuse rating needed for a circuit that carries a maximum current of 10 A, with a safety margin of 25%.

Answer: Fuse rating = maximum current × safety margin = 10 A × 1.25 = 12.5 A. Therefore, choose a fuse rated at 13 A.

Question 5: Explain why it is important to select a fuse with the correct rating for a circuit.

Answer: Selecting a fuse with the correct rating ensures that it provides adequate protection without nuisance blowing. If the fuse rating is too low, it may blow during normal operation, causing unnecessary interruptions. If too high, it may not protect the circuit effectively against overloads, risking damage to equipment and safety hazards.

Question 6: Design a simple experiment to test the operation of a fuse in a circuit, including variables to control.

Answer: Set up a circuit with a power supply, a fuse, and a variable resistor or bulb. Gradually increase the current using the variable resistor until the fuse blows. Control variables such as the voltage supply and the type of fuse used. Safety precautions include turning off the power before replacing the fuse and ensuring all connections are secure.

Question 7: A fuse rated at 5 A blows when the current reaches 4.8 A. Explain why this might happen and if the fuse rating should be adjusted.

Answer: Fuses can blow slightly below their rated current due to manufacturing tolerances, temperature, or impurities. Since the fuse is rated at 5 A and blows at 4.8 A, it is functioning correctly. No adjustment is needed unless frequent blowing occurs at currents well below the rated value.

Question 8: Describe how the use of a fuse enhances safety in household electrical systems.

Answer: A fuse prevents excessive current from flowing through household wiring, reducing the risk of overheating, electrical fires, and damage to appliances. It acts as a safety barrier by disconnecting the circuit when dangerous overloads occur.

Question 9: Identify a real-world application where fuses are critical and explain why.

Answer: Fuses are critical in automobiles to protect wiring and electronic components from overloads and short circuits, preventing damage and reducing fire hazards.

Question 10: What is the main difference between a fuse and a circuit breaker?

Answer: A fuse contains a wire that melts when overloaded, requiring replacement after it blows, whereas a circuit breaker uses an electromagnetic or thermal mechanism to trip and can be reset without replacement.