Which statement correctly differentiates a bus bar from a wiring diagram in aircraft maintenance?

• A. A wiring diagram shows the wiring layout and circuit functions; a bus bar distributes power to multiple circuits.
• B. A bus bar distributes power to multiple circuits from a single source; a wiring diagram shows the wiring layout and circuit functions.
• C. A bus bar stores energy; a wiring diagram stores schematics.
• D. A wiring diagram routes physical power; a bus bar lists service bulletins.

Answer: (B)

A bus bar is the central conductor that distributes power from a single source to multiple circuits. A wiring diagram, by contrast, is a schematic view that shows how wires are laid out, where they run, and what each circuit does. In aircraft electrical systems, you’ll see power come into a bus bar and be handed off to numerous loads through feeders, keeping the power distribution organized and centralized. The wiring diagram helps you trace those wires, identify connections, and understand circuit functions—useful for installation, troubleshooting, and maintenance, but it does not serve as the physical power-distribution point itself.

Other descriptions don’t fit because a bus bar does not store energy—that’s the role of a battery or capacitor—nor does a wiring diagram store schematics; it conveys how wires connect and what each circuit controls. A diagram isn’t about routing physical power, and service bulletins are separate documents, not part of how a bus bar vs. wiring diagram function.