How is the efficiency of a light bulb calculated?

The efficiency of a light bulb is calculated by comparing the useful energy output to the total energy input. This is done by determining how much of the energy consumed by the bulb is converted into light energy, which is the desired useful output, versus how much energy is wasted as heat or not utilized for lighting. The formula for efficiency can be expressed as a percentage, where efficiency equals the useful output energy divided by the total input energy, multiplied by 100. This approach effectively highlights the light bulb's performance and helps consumers choose more energy-efficient options.

In contrast, measuring brightness alone does not provide a complete view of efficiency since it doesn't account for the energy consumed to produce that brightness. Examining material quality may give insights into the potential for efficiency but does not directly measure it. Using Ohm's law relates to electrical resistance and current flow but does not directly pertain to calculating efficiency in the context of light bulbs.