What is the SI unit of resistance?

The SI unit of resistance is the ohm.

Understanding Resistance and the Ohm

Resistance is a fundamental property of electrical circuits that opposes the flow of electric current. It's measured using the ohm, symbolized by the Greek letter Ω. According to the provided reference, one ohm (1 Ω) is defined as the resistance offered by a conductor when a current of one ampere (1 A) flows through it while a potential difference of one volt (1 V) is applied across it. This definition is closely related to Ohm's Law, which states that the voltage across a conductor is directly proportional to the current flowing through it, with the constant of proportionality being the resistance.

Key Points About the Ohm

• Symbol: The symbol for ohm is Ω (the Greek capital letter omega).
• Definition: A conductor has a resistance of 1 ohm when a potential difference of 1 volt applied across it results in a current of 1 ampere flowing through it.
• Practical Application: The ohm is used in electrical and electronic engineering to measure the resistance of components like resistors, wires, and other materials.

How Resistance Works

Resistance is a measure of how difficult it is for electric current to pass through a material. Different materials have different resistances. For example:

• Conductors like copper and silver have very low resistance.
• Insulators like rubber and plastic have very high resistance.
• Resistors, used in electronics, have specific resistance values designed to control current flow.

Examples

• A typical resistor in an electronic circuit might have a resistance of 100 ohms (100 Ω).
• A length of wire might have a very small resistance, perhaps a fraction of an ohm.
• An insulator could have a resistance of millions or even billions of ohms.

Table of Resistance Units

In summary, the ohm is the standard unit used to measure electrical resistance, reflecting how much a material opposes the flow of electric current.