What happens when you have a 6 amp line fuse supplying a 12 amp ups?

If a 6 amp line fuse is used to supply a 12 amp uninterruptible power supply (UPS), the fuse will likely blow or trip as soon as the UPS attempts to draw more current than the fuse can handle. This occurs because the fuse is designed to protect the circuit by breaking the connection when the current exceeds its rated capacity. As a result, the UPS will not function properly, and any connected devices will lose power. To safely operate the UPS, it is essential to use a fuse that matches or exceeds its current requirements.