Question T0A05
From subelement T0 - T0A
Why should a 5-ampere fuse never be replaced with a 20-ampere fuse?
Why is this correct?
A 20-ampere fuse allows four times more current than the 5-ampere rating. The original 5A fuse was sized to protect specific wires and components in the circuit. When excessive current flows beyond the equipment's design limits, wires and components overheat rapidly, creating fire risk. The larger fuse fails to interrupt dangerous current levels, defeating the protective purpose. Option A is wrong—higher-rated fuses are less likely to blow. Option B is incorrect—fuses don't affect power supply ripple.
Memory tip
Always match fuse ratings exactly to manufacturer specifications. Think of fuses as circuit-specific speed limits—using the wrong rating is like removing speed limits from dangerous curves. The equipment determines the safe current threshold, not your convenience or desire for 'extra headroom.'
Learn more
Fuses protect against overcurrent conditions by creating an intentional weak point that fails safely before damage occurs. In amateur radio stations, proper fuse selection follows equipment specifications to ensure emission standards compliance and prevent spurious radiation from damaged circuits. Mobile installations require particular attention since automotive environments present additional current surge risks during engine starting and alternator regulation.
Think about it
Why do you think equipment manufacturers spend time calculating exact fuse ratings rather than just recommending 'use the biggest fuse that fits'?