Electricity flows through a circuit, a closed loop from a power source, through a conductor such as copper wire, to a load like a bulb or appliance, and back, and basic concepts include voltage (the electrical 'pressure' pushing current, measured in volts), current (the flow of electricity, measured in amps), and resistance. Common electrical hazards on a building site include exposed or damaged wiring, overloaded circuits, working near live wires without isolating the power first, and using electrical equipment in wet conditions, all of which carry risk of shock, fire, or electrocution. In most countries, including Nigeria, wiring a building's electrical system is work reserved for a licensed or certified electrician, not general laborers, because incorrect wiring is a leading cause of house fires and electrical injuries. A non-electrician on a construction team should understand enough to recognize hazards, follow lockout procedures before work near electrical systems, and know that any fault, spark, or exposed live wire should be reported immediately rather than handled personally.