Voltage drop describes the decrease in voltage as electrical energy moves from the source to the load through a circuit. When current flows, the resistance of wires and other components uses up some of that voltage, so the voltage reaching the load is lower than what the source provides. The amount of drop on any portion of the circuit is basically V = I × R, so longer runs or smaller, higher‑resistance conductors cause a larger drop. In practice, you design to keep this drop within acceptable limits so devices at the load still receive enough voltage to operate properly. For example, in a 120 V system, a significant drop can mean the load gets noticeably less than 120 V, which can affect performance. To reduce voltage drop, you can use larger conductor sizes, shorten the run, or reduce current. This definition isn’t about the total resistance of the circuit, which is a separate concept used to determine current. It isn’t about the maximum permissible current (ampacity), which relates to heating limits. And it isn’t about insulation thickness, which concerns isolation and dielectric properties rather than the voltage delivered to the load.