Why should a 5-ampere fuse never be replaced with a 20-ampere fuse?
The correct answer is C: Excessive current could cause a fire. A 5-ampere fuse should never be replaced with a 20-ampere fuse because excessive current could cause a fire. The 5-amp fuse was selected to protect wiring that can only safely handle 5 amps. A 20-amp fuse would allow 4 times more current, which could overheat the wiring and start a fire before the fuse blows. For amateur radio operators, this is a critical safety rule - always replace fuses with the same rating. Using a larger fuse defeats the protection.
Exam Tip
Never replace 5A fuse with 20A = fire hazard. Think 'L'arger fuse = 'L'ess protection = 'L'ikely fire. Allows excessive current that can overheat wiring and cause fire. Always use the same rating.
Memory Aid
"Never replace 5A fuse with 20A = fire hazard. Think 'L'arger fuse = 'L'ess protection. Allows excessive current that can overheat wiring and cause fire. Always replace with the same rating."
Real-World Application
Your equipment has a 5-amp fuse protecting wiring rated for 5 amps. You replace it with a 20-amp fuse because the 5-amp keeps blowing. Now, if a fault draws 15 amps, the 20-amp fuse doesn't blow, but the wiring can only handle 5 amps. The wiring overheats and could start a fire. The original 5-amp fuse was correctly sized to protect the wiring.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. A larger fuse wouldn't be more likely to blow - it would be less likely to blow, which is the problem. It allows dangerous currents that the smaller fuse would stop.
Option B: Incorrect. Power supply ripple isn't affected by fuse size - ripple comes from the power supply design, not fuse rating.
Option D: Incorrect. Since A and B are not correct, 'all of the above' cannot be correct. Only fire hazard is the real danger.
题目解析
The correct answer is C: Excessive current could cause a fire. A 5-ampere fuse should never be replaced with a 20-ampere fuse because excessive current could cause a fire. The 5-amp fuse was selected to protect wiring that can only safely handle 5 amps. A 20-amp fuse would allow 4 times more current, which could overheat the wiring and start a fire before the fuse blows. For amateur radio operators, this is a critical safety rule - always replace fuses with the same rating. Using a larger fuse defeats the protection.
考试技巧
Never replace 5A fuse with 20A = fire hazard. Think 'L'arger fuse = 'L'ess protection = 'L'ikely fire. Allows excessive current that can overheat wiring and cause fire. Always use the same rating.
记忆口诀
Never replace 5A fuse with 20A = fire hazard. Think 'L'arger fuse = 'L'ess protection. Allows excessive current that can overheat wiring and cause fire. Always replace with the same rating.
实际应用示例
Your equipment has a 5-amp fuse protecting wiring rated for 5 amps. You replace it with a 20-amp fuse because the 5-amp keeps blowing. Now, if a fault draws 15 amps, the 20-amp fuse doesn't blow, but the wiring can only handle 5 amps. The wiring overheats and could start a fire. The original 5-amp fuse was correctly sized to protect the wiring.
错误选项分析
Option A: Incorrect. A larger fuse wouldn't be more likely to blow - it would be less likely to blow, which is the problem. It allows dangerous currents that the smaller fuse would stop. Option B: Incorrect. Power supply ripple isn't affected by fuse size - ripple comes from the power supply design, not fuse rating. Option D: Incorrect. Since A and B are not correct, 'all of the above' cannot be correct. Only fire hazard is the real danger.
知识点
Fuse replacement, Overcurrent protection, Fire hazard, Electrical safety
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.