You must design a fuse for a device operating at 230 V and 5 A. Which fuse rating would you choose and why? What can go wrong if the rating is too low or too high?

Solution & explanation

Choose the manufacturer-specified fuse with suitable voltage, breaking capacity and time characteristic. In a simplified exercise choose the smallest suitable standard current rating just above normal 5 A, for example 6 A if appropriate. Too low can interrupt normal use; too high may fail to protect the wiring. Voltage and operating current alone do not determine an exact safe fuse for a real device.