Which statement is true regarding the use of a clamp-on ammeter?

• A. Place the jaws around multiple conductors at once.
• B. The meter must be connected in series to measure current.
• C. Place the jaws around a single conductor at a time.
• D. Clamp-on meters measure resistance.

Answer: (C)

Clamp-on ammeters measure current by sensing the magnetic field formed around a conductor. The jaws form a magnetic path around one conductor, so the reading reflects that conductor’s current. If you clamp around multiple conductors, the magnetic effects can add or cancel, leading to an incorrect measurement. That’s why the proper technique is to place the jaws around a single conductor at a time. You don’t connect a clamp-on meter in series in the circuit because it measures the current without interrupting the circuit. Also, these meters don’t measure resistance—that’s done with an ohmmeter or the resistance function on a multimeter.