Electrician Red Seal · Question
An electrician is using a clamp-on ammeter to measure the current draw of a 120 V household appliance. The appliance has a two-conductor cord. To get an accurate reading, how should the clamp-on ammeter be used?
A clamp-on ammeter measures current by detecting the magnetic field produced by current flowing through a single conductor. To get an accurate reading, the clam
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Question: An electrician is using a clamp-on ammeter to measure the current draw of a 120 V household appliance. The appliance has a two-conductor cord. To get an accurate reading, how should the clamp-on ammeter be used?
Answer options:
- Clamp around both the hot and neutral conductors simultaneously.
- Clamp around only the ground conductor. ✅ Clamp around a single conductor (hot or neutral) while the appliance is operating.
- Clamp around the entire cord, including the outer jacket.
Correct answer: Clamp around a single conductor (hot or neutral) while the appliance is operating.
Explanation: A clamp-on ammeter measures current by detecting the magnetic field produced by current flowing through a single conductor. To get an accurate reading, the clamp must encircle only one current-carrying conductor (either the hot or the neutral). If clamped around both hot and neutral, the magnetic fields cancel out, resulting in a zero or near-zero reading. Clamping around the entire cord or only the ground conductor will not yield an accurate measurement of load current.
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