Black and yellow wires in the distribution box

In most electrical systems, black wires are typically “hot” or live wires carrying current, while yellow wires are often used as switched or secondary live conductors, and in some IEC systems, yellow may indicate a protective earth in combination with green.Black WiresBlack wires are almost always hot wires, meaning they carry live electrical current from the breaker panel to outlets, switches, or appliances. They are the main power-carrying conductors in a circuit and should always be treated as live until the circuit is de-energized. In single-phase AC systems, black is commonly used for Line 1, while in three-phase systems, black may serve as one of the line conductors . When connecting devices, black wires typically attach to brass-colored screws on outlets or switches.Yellow WiresYellow wires are often used as switched hot wires or secondary live conductors in AC circuits. For example, they may carry current to a light controlled by a switch or serve as a traveler wire in multi-way switch setups . In IEC (International Electrotechnical Commission) standards, yellow is sometimes combined with green stripes to indicate a protective earth conductor, providing a safe path for fault current to prevent electric shock . The exact function of a yellow wire can vary depending on local wiring practices and the type of installation.Safety ConsiderationsAlways turn off the breaker before touching any wires in a distribution box.Use a voltage tester to confirm that wires are de-energized.Never assume a wire's function solely based on color; verify with proper testing, especially in older or non-standard installations.Follow local electrical codes (NEC in the U.S., IEC in Europe) for proper identification and connection .SummaryBlack wire: primary hot/live wire, carries current from the panel.Yellow wire: secondary hot, switched live, or in IEC systems, part of protective earth (green/yellow).Always verify wire function with testing and adhere to safety standards to prevent shock or fire hazards. Understanding these color codes ensures safe installation, maintenance, and troubleshooting of electrical circuits in residential, commercial, or industrial settings .