$\text{[math]}$

An electric current is formed by the flow of charge carriers through a conducting material, similar to water flowing through a pipe. The base SI unit ampere (A) is defined in terms of the current flow required to generate a specific force of 2 × 10⁻⁷ newtons between two wires of infinite length one metre apart in a vacuum. When current flows in a wire, an electromagnetic field is produced. As adjacent magnetic fields interact, the two wires with current flowing will exert an attractive or repulsive force upon each other. One ampere of current represents one coulomb of electrical charge (6.241 × 10¹⁸ charge carriers) moving past a cross-section of conductor in one second.

$\text{[math]}$

Voltage is measured in volts (SI unit). It is the ‘driving force’ or ‘pressure’ which causes electrons to flow. The volt is defined as the potential difference between two points in an electric circuit that will impart one joule of energy per coulomb of charge that passes through it.

$\text{[math]}$

Applied science

What is resistance? What are resistors?

Resistance is the characteristic of a material that impedes the flow of electrons. All materials have some degree of resistance; the amount of resistance depends on the individual properties of the material. The flow of electrons through a resistant material generates heat.

Ohm is the unit of measure for electrical resistance. It is defined as the resistance between two points when a constant potential difference of one volt produces a current of one ampere. This relationship is known as Ohm’s law. Mathematically, the relationship between electrical current, resistance and voltage is described as:

$\text{[math]}$