What is an ohm?

An ohm is defined as the unit of electrical resistance in the International System of Units (SI). It quantifies how strongly a material resists the flow of electric current. In practical terms, one ohm is the resistance that allows one ampere of current to flow when one volt is applied across it. This relationship is described by Ohm's Law, which states that voltage (V) equals current (I) multiplied by resistance (R), or V = IR.

Understanding the nature of electrical resistance is fundamental in fields involving electricity and electronics. Resistance affects how easily electric current can flow through materials, which is crucial for designing circuits and understanding how various substances and devices interact with electric currents.

The other choices refer to different aspects of electrical theory: voltage is measured in volts, current in amperes, and power in watts. Each of these plays a significant role in electrical systems, but they do not represent resistance, which is the specific domain of ohms. Thus, identifying ohms as the unit of electrical resistance not only demonstrates knowledge of electrical terminology but also reveals a broader understanding of how electrical circuits operate.