Which instrument is used to measure electric current?
The correct answer is D: An ammeter. An ammeter is used to measure electric current. Current is the flow of electric charge, measured in amperes (amps). Ammeters are designed specifically for this purpose and are connected in series with the circuit to measure current flow. For amateur radio operators, ammeters (often part of a multimeter) are essential tools for checking power supply current draw, measuring transmitter current, troubleshooting circuits, and verifying equipment power consumption. Understanding how to use an ammeter is fundamental to electronics work and power management.
Exam Tip
Ammeter = measures current (amperes). Think 'A'mmeter = 'A'mperes (current). Ohmmeters measure resistance, electrometers measure small charges, voltmeters measure voltage - none measure current.
Memory Aid
"Ammeter = measures Amperes (current). Think 'A'mmeter = 'A'mperes. Measures the flow of electric charge through a circuit."
Real-World Application
You need to check how much current your transceiver draws from the power supply. You connect an ammeter in series with the power supply output. The ammeter shows 8 amperes, telling you the transceiver's current consumption. This helps you select an appropriate power supply and understand power requirements.
Key Concepts
Why Other Options Are Wrong
Option A (Ohmmeter): Incorrect. An ohmmeter measures resistance (ohms), not current. Resistance and current are different electrical quantities.
Option B (Electrometer): Incorrect. An electrometer measures very small electric charges or currents, typically used in scientific applications. It's not the standard instrument for measuring current.
Option C (Voltmeter): Incorrect. A voltmeter measures voltage (electric potential), not current. Voltage and current are different measurements.
题目解析
The correct answer is D: An ammeter. An ammeter is used to measure electric current. Current is the flow of electric charge, measured in amperes (amps). Ammeters are designed specifically for this purpose and are connected in series with the circuit to measure current flow. For amateur radio operators, ammeters (often part of a multimeter) are essential tools for checking power supply current draw, measuring transmitter current, troubleshooting circuits, and verifying equipment power consumption. Understanding how to use an ammeter is fundamental to electronics work and power management.
考试技巧
Ammeter = measures current (amperes). Think 'A'mmeter = 'A'mperes (current). Ohmmeters measure resistance, electrometers measure small charges, voltmeters measure voltage - none measure current.
记忆口诀
Ammeter = measures Amperes (current). Think 'A'mmeter = 'A'mperes. Measures the flow of electric charge through a circuit.
实际应用示例
You need to check how much current your transceiver draws from the power supply. You connect an ammeter in series with the power supply output. The ammeter shows 8 amperes, telling you the transceiver's current consumption. This helps you select an appropriate power supply and understand power requirements.
错误选项分析
Option A (Ohmmeter): Incorrect. An ohmmeter measures resistance (ohms), not current. Resistance and current are different electrical quantities. Option B (Electrometer): Incorrect. An electrometer measures very small electric charges or currents, typically used in scientific applications. It's not the standard instrument for measuring current. Option C (Voltmeter): Incorrect. A voltmeter measures voltage (electric potential), not current. Voltage and current are different measurements.
知识点
Ammeters, Current measurement, Electric current, Test equipment
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.