A plug fuse is typically used in which type of circuit?

A plug fuse is commonly used in branch circuits, and this is why it is the correct choice. Branch circuits are the pathways that distribute electrical power from the service equipment to various outlets and devices in a building. Since plug fuses are designed to protect specific circuits by disconnecting power when the current exceeds a certain limit, they are well-suited for branch circuit usage.

These circuits typically include lighting and outlet circuits where individual devices can be connected, making it important to have overcurrent protection that can isolate faults without affecting the entire electrical system. Plug fuses are specifically designed to be replaced easily and can provide reliable protection for branch circuits, which often carry variable loads.

In contrast, main circuits generally require circuit breakers or larger fuses that can handle the overall load of the entire electrical system. Sub-circuits may not require the same level of individual protection as branch circuits. Transformer circuits usually utilize specialized protection devices tailored to their specific operational requirements. Thus, the application of plug fuses aligns most closely with the operational characteristics of branch circuits.