CSLB C-10 Electrical ContractorSafety and TestingMedium
An electrician is checking for proper grounding of a newly installed 120V receptacle. Using a multimeter, what voltage reading should be observed between the hot (small slot) and the equipment grounding conductor (round hole) of a properly wired and grounded receptacle?
- AApproximately 0V
- BApproximately 120V
- CAn open circuit reading (OL)
- DApproximately 240V
Show answer & explanationAnswer & explanation
Correct answer: B. Approximately 120V
In a properly wired 120V receptacle, the hot conductor carries 120V relative to ground. Therefore, a multimeter connected between the hot slot and the equipment grounding conductor (which is bonded to ground) should read approximately 120V, indicating correct wiring and grounding.
Why the other options are wrong
- A. 0V between hot and ground would indicate a wiring fault or no power.
- C. An open circuit reading would indicate a break in the hot conductor or a faulty connection.
- D. 240V would indicate a wiring error for a 120V circuit or a different system type.
Receptacle Grounding Test
To verify proper grounding of a 120V receptacle, a multimeter measurement between the hot (small slot) and the equipment grounding conductor (round hole) should yield approximately 120 volts.
- Hot to ground should read nominal circuit voltage.
- Hot to neutral should read nominal circuit voltage.
- Neutral to ground should read near 0 volts.
- Tests for proper wiring and safety.
Memory trick: Hot to Ground, 120 is Found!