What is the primary cause of a fuse becoming excessively hot?

The primary cause of a fuse becoming excessively hot is indeed related to loose clamps in the fuse holder. When a fuse is installed, it relies on a secure connection to ensure that electrical current flows efficiently through it. If the clamps or connections in the fuse holder are loose, it can lead to increased resistance at the junction where the fuse meets the holder. This increased resistance generates heat, resulting in the fuse becoming excessively hot.

In contrast, while the age of the fuse, overcurrent situations, and environmental factors can potentially impact a fuse's performance, they do not primarily cause overheating. An old fuse may be more prone to failure, but age alone does not create the conditions for excessive heat. Overcurrent situations can definitely cause a fuse to blow, but it is the condition of the connection that directly leads to heat build-up when it comes to loose connections. Environmental factors may contribute to temperature changes, but they are not a primary cause in the context of fuse overheating. Thus, the connection integrity is critical, making loose clamps in the fuse holder the primary reason for a fuse becoming excessively hot.