What is the standard color code for the DC supply, and how is it used in wiring checks?

• A. Red denotes positive, black or blue denotes negative; used to identify power rails and ensure correct probe connections.
• B. Red denotes negative; black or blue denotes positive.
• C. Blue denotes positive, Red denotes negative.
• D. Green denotes positive, Yellow denotes negative.

Answer: (A)

Red is positive and black or blue is negative in DC power wiring. This color convention lets you quickly identify which wire carries the supply and where to place test probes during checks. When wiring checks are performed, you connect the red lead to the positive power rail and the black (or blue) lead to the return/negative path, then verify with a meter that polarity is correct and there are no cross-connections. Using this color-coding consistently helps prevent reverse polarity and mistaken connections, making it easier to spot improper wiring during maintenance.