Testing & TroubleshootingQuestion 511 of 521
A non-contact voltage tester (NCVT) does not light up near a conductor you must work on. Before treating the conductor as dead, what is the correct action?
a.Trust the NCVT completely and begin work
b.Assume the conductor is a neutral and cut it
c.NCVTs are infallible, so no further check is needed
d.Confirm de-energization with a contact voltage tester using live-dead-live, since NCVTs can miss voltage (shielding, ganged wires, low sensitivity)
Explanation
An NCVT is only a first indicator; it can fail to detect voltage due to shielding, cable geometry, or dead batteries, so it must never be the sole basis for calling a conductor dead. Verify with a contact tester using the live-dead-live method before touching conductors. Trusting it blindly (a, c) or guessing it's a neutral (b) can be fatal.
Practice all 521 questions free — no signup required.
Related questions on this topic
- In a series circuit, 24 V is applied across a 4 ohm and an 8 ohm resistor in series. What voltage will a DMM read across the 8 ohm resistor?
- A branch-circuit breaker trips instantly every time it is reset, with nothing plugged in. Continuity from hot to ground reads near 0 ohms. What is the most likely fault?
- Three parallel loads on a 120 V circuit draw 4 A, 6 A, and 5 A respectively. What total current should a clamp meter read on the feeder conductor?
- A single-phase load operates at 240 V and draws 20 A at unity power factor. What is its power in kilowatts?
- Before connecting a three-phase motor to a new feeder, why would you use a phase-rotation (phase-sequence) meter on the supply?
- Using the rule of thumb of 1 megohm minimum per 1,000 V of rating, what is the minimum acceptable insulation resistance for a 4,160 V motor?
Last reviewed: · editorial process
PrepPass Editorial Team · Verified against California CSLB C-10 Electrical Trade Examination · How we review