Voltage Drop

The loss of voltage along a wire run, caused by the resistance of the wire itself. Long runs and undersized wire make lights dim and motors run hot.

Wire is not a perfect conductor: every foot eats a little voltage, and the more current you pull, the more it eats. Code design practice keeps total drop around 5% or less, which is why a detached garage 150 feet from the house needs noticeably thicker wire than the same circuit would inside.

Symptoms of excessive drop are familiar: lights that dim when a vacuum starts, power tools that feel weak at the end of a long extension cord, well pumps and AC compressors that run hot and die young. The fix is engineering, not gadgets: shorter runs, larger wire gauge, or a subpanel placed closer to the load.

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More in Volts, Amps & Watts
  • Amp (Ampere) : The unit of electrical current: how much electricity is flowing through a wire at a given moment.
  • Volt : The unit of electrical pressure pushing current through a circuit.
  • Watt & Kilowatt : The unit of electrical power: volts multiplied by amps.
  • Kilowatt-Hour (kWh) : The unit your utility bills you for: one kilowatt of power used for one hour.

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