Voltage drop in 1 km cable: difference between coiled (on drum) vs laid cable?

The discussion addresses the discrepancy between measured and calculated voltage drop in a 1 km, 24 VDC cable wound on a drum. The measured voltage drop was negligible, contrary to the expected ~8 V drop based on calculations. Key points highlight that voltage drop depends on current flow; if the load (a switch at the cable end) draws little or no current, voltage drop will be minimal. The presence of a switch alone does not cause current draw unless it closes a circuit. Calculations should consider cable resistance, which depends on conductor material, length, and cross-sectional area (AWG). The cable’s resistance can be estimated using R = ρL/A, where ρ is the resistivity. One response suggests that inductive effects from the cable being coiled on a drum might influence measurements, but the primary factor remains current flow and load conditions. Proper measurement requires the cable to be under load with current flowing to observe voltage drop accurately.
Summary generated by the language model.