ARRL Technician Practice Exam

Why is it unwise to install a 20-ampere fuse in place of a 5-ampere fuse?

1. It may cause appliances to underperform

2. Excessive current could cause a fire

3. It will not fit in the holder

4. It can lead to a power surge

The correct answer is: Excessive current could cause a fire

Using a 20-ampere fuse in place of a 5-ampere fuse is unwise because the higher-rated fuse won't blow when excessive current flows through the circuit. The function of a fuse is to protect the wiring and devices in a circuit by breaking the circuit when the current exceeds a safe level. If the circuit is overloaded or if a fault occurs, a 5-ampere fuse would blow to prevent overheating and potential fire hazards. However, a 20-ampere fuse would allow too much current to flow before it blows, significantly increasing the risk of overheating wires and potentially causing a fire. The other choices provided do not accurately capture the main risk associated with using an incorrect fuse rating. Appliances could possibly underperform, but that is not the critical concern in this scenario. While a 20-ampere fuse might physically fit in the holder, this is not relevant to the electrical safety issue at hand. Finally, while a power surge can cause problems, it is not directly related to the use of a higher-rated fuse in place of a lower-rated one. The key takeaway here is that using the correct fuse rating is paramount to ensuring safety and preventing potentially dangerous situations.