You place a clamp-on ammeter around an extension cord powering a running 12A space heater, but the meter reads 0.00A. What is the reason for this reading?
Answers
AThe ammeter is set to DC instead of AC
BThe extension cord is shielded
CThe clamp is around both the hot and neutral wires, canceling out the magnetic fields
DThe heater is operating at 100% efficiency
Correct answer: C — The clamp is around both the hot and neutral wires, canceling out the magnetic fields
A clamp meter must be placed around a single conductor (the hot or the neutral). If placed around the entire cable, the opposing currents cancel the magnetic field, resulting in a zero reading.
MIFOTRA exam practicealigned to NFPA 70 / IEC 60364·1 mark·Easy