ARRL Technician Practice Exam

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What unit is used to express electrical resistance?

Watt
Volt
Ampere
Ohm

The correct answer is: Ohm

The unit used to express electrical resistance is the Ohm. This unit is named after the German physicist Georg Simon Ohm, who formulated Ohm's Law. Ohm's Law defines the relationship between voltage (measured in volts), current (measured in amperes), and resistance (measured in ohms). According to this law, resistance can be understood as the opposition to the flow of electric current in a circuit. When a voltage is applied across a resistor, it creates a current that is inversely proportional to the resistance—higher resistance results in lower current for a given voltage. Understanding resistance is crucial in circuit design and analysis, as it affects how much current will flow through different components. The other units mentioned relate to different electrical properties: watts measure power, volts measure electrical potential, and amperes measure current. Therefore, recognizing that ohms specifically denote resistance is key to understanding basic electrical concepts.