What is the basic unit of electrical resistance?

• A. Volt
• B. Ampere
• C. Ohm
• D. Watt

Answer: (C)

The basic unit used to quantify how strongly a material resists electric current is the ohm. An ohm is defined as the resistance between two points of a conductor when a constant potential difference of one volt, applied to those points, produces a current of one ampere with no electromotive force present. In practical terms this means resistance is what you get when you divide voltage by current (R = V / I); one volt per one ampere equals one ohm. The ohm is a derived unit, equal to volt divided by ampere. The other terms—volt, ampere, and watt—describe voltage (the driving force), current (the flow of electrons), and power (the rate of energy transfer or heat), respectively. So, for any given voltage, higher resistance means less current, which is why resistance is a key factor in heat generation and conductor sizing in electrical plans. Temperature, material, length, and cross‑sectional area all influence resistance.