The ohm - (symbol: Ω)

The ohm (symbol: Ω) is the SI derived unit of electrical resistance, named after German physicist Georg Ohm. Various empirically derived standard units for electrical resistance were developed in connection with early telegraphy practice, and the British Association for the Advancement of Science proposed a unit derived from existing units of mass, length and time, and of a convenient scale for practical work as early as 1861. As of 2020, the definition of the ohm is expressed in terms of the quantum Hall effect.

The ohm is defined as an electrical resistance between two points of a conductor when a constant potential difference of one volt, applied to these points, produces in the conductor a current of one ampere, the conductor not being the seat of any electromotive force.

Ohm (Ω) is the unit of electrical resistance, indicating how much a material or component opposes the flow of electric current. In the context of light bulbs and luminaires, Ohm's law and the concept of electrical resistance play a role in understanding how these devices operate within an electrical circuit.

Ohm's Law states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) between them. Mathematically, Ohm's Law is represented as:

I = V / R

In the case of light bulbs and luminaires, these devices have a certain resistance to the flow of electric current. When you connect a light bulb or luminaire to a power source (such as a battery or an electrical outlet), the voltage across the device creates a potential difference that drives the electric current through it. The resistance of the device limits the amount of current that can flow, which in turn affects the brightness and performance of the light.

Here's how Ohm's Law applies to light bulbs and luminaires:

• Voltage (V): The voltage supplied by the power source determines the potential difference across the light bulb or luminaire. A higher voltage will result in a higher potential difference and can lead to a brighter light, assuming the resistance remains constant.
• Resistance (R): The resistance of the light bulb or luminaire affects how much current can flow through it. Light bulbs are designed to have a specific resistance that allows them to emit light without getting damaged. The resistance also plays a role in determining the amount of heat generated by the device.
• Current (I): The current flowing through the light bulb or luminaire determines its brightness. According to Ohm's Law, for a given voltage, if the resistance increases, the current decreases, leading to a dimmer light. Conversely, if the resistance decreases, the current increases, resulting in a brighter light.

It's important to note that incandescent light bulbs, which were commonly used in the past, follow Ohm's Law relatively closely. However, newer lighting technologies like fluorescent lamps, LED lamps and other energy-efficient options might exhibit more complex electrical behaviors due to their internal electronic components.

In summary, Ohm's Law and the concept of electrical resistance provide a foundation for understanding how light bulbs and luminaires function within an electrical circuit. The resistance of these devices, along with the applied voltage, influences the current flow and, consequently, the brightness and performance of the light they produce.