Which two variables affect the clearing time of a fuse?

The clearing time of a fuse is primarily influenced by the current flowing through the fuse and the duration of that current flow. When the current exceeds the fuse's rated level, it generates heat due to resistance in the conductive materials. The higher the current, the faster the fuse will heat up to the point where it can no longer withstand this thermal load, leading to its rapid clearing or melting.

Time is also a crucial factor because it considers how long the excessive current has been flowing. Fuses have specific time-current characteristics, which dictate how long they can handle overcurrents before they blow. For instance, a short-circuit condition results in a very high current that leads to a quick reaction, whereas an overload may allow for a longer duration before the fuse clears.

This understanding of current and the time factor is critical for designing electrical systems that ensure safety and reliability. The other options do not directly relate to how fast a fuse clears, making them less relevant in this context.