Final answer:
A chain is useful for fishing wire through conduit because of its rigidity and weight, which allows it to navigate the conduit's bends and turns, enabling electricians to pull wires through effectively.
Step-by-step explanation:
Chain is useful as a means of fishing wire through conduit because it is heavy and rigid enough to be pushed through the tubing without folding back on itself. Much like a plumber might use a snake to clear a pipe, electricians use a chain to guide wires through the protective conduits that house electrical wiring. The weight of the chain helps it to navigate through turns and bends within the conduit, and once one end of the chain emerges at the intended exit point, the wire or cable can be attached to the end of the chain and pulled back through the conduit to complete the installation. For example, when using a ball chain, the individual balls can roll over each other, allowing the chain to bend and curve without getting stuck. This makes it much easier to navigate through tight corners.