If a plug fuse window appears clear and the element is merely broken, the probable cause of the fuse blowing is?

• A. A short circuit
• B. An overload
• C. A change in electrical value
• D. None of the above

Answer: (B)

The likely cause is an overload. A fuse opens when the current exceeds its rating, and when the element overheats over time, it can break while the glass window remains clear. If a short circuit had occurred, you’d typically see more rapid, dramatic damage or scorching from the high fault current. A change in electrical value isn’t by itself a cause for a fuse to blow. So, the pattern described—clear window and a broken element—fits an overload condition where the circuit drew more current than the fuse could handle for a period.