Which instrument is commonly used to measure current in a circuit?

Which instrument is commonly used to measure current in a circuit?

• A. Voltmeter
• B. Ammeter
• C. Oscilloscope
• D. Ohmmeter

Answer: (B)

Measuring current directly requires a device that is placed in series with the circuit so the same current flows through both the circuit and the meter. An ammeter is designed for that exact purpose; it has very low internal resistance to minimize voltage drop and disturbance to the circuit, and it displays the current flowing through the path. This makes the ammeter the best choice for measuring current. A voltmeter, by contrast, is connected in parallel to measure voltage across a component and doesn’t provide a direct current reading. An oscilloscope displays voltage waveforms and, unless used with a current probe or a sense resistor, doesn’t directly read current. An ohmmeter measures resistance and is used with the circuit powered off, not for measuring current in an energized circuit.

Measuring current directly requires a device that is placed in series with the circuit so the same current flows through both the circuit and the meter. An ammeter is designed for that exact purpose; it has very low internal resistance to minimize voltage drop and disturbance to the circuit, and it displays the current flowing through the path.

This makes the ammeter the best choice for measuring current. A voltmeter, by contrast, is connected in parallel to measure voltage across a component and doesn’t provide a direct current reading. An oscilloscope displays voltage waveforms and, unless used with a current probe or a sense resistor, doesn’t directly read current. An ohmmeter measures resistance and is used with the circuit powered off, not for measuring current in an energized circuit.