What is the purpose of a voltage drop test in troubleshooting?

• A. To locate high resistance sections by measuring voltage loss along a conductor.
• B. To measure the total circuit current.
• C. To test insulation resistance.
• D. To check voltage regulator function.

Answer: (A)

Voltage drop testing is used to locate high resistance sections in a live circuit by measuring how much voltage is lost along a conductor under load. By applying a known current through the circuit and measuring the voltage at various points, you can apply V = I × R for each segment. If a large portion of the supply voltage appears to disappear across a particular segment, that section has higher resistance, signaling a bad connection, corrosion, loose terminal, or damaged wire. This technique helps pinpoint where the fault is so you can repair the exact spot rather than guess along the entire run.

This isn’t about measuring total circuit current, which just tells you how much current is flowing overall. It also isn’t a test of insulation resistance, which looks at leakage to ground or between conductors, nor is it a test of whether the voltage regulator is maintaining output.