The ratio of the total luminous flux emitted by the light source to the electric power (watt) consumed by the light source is called the luminous efficiency of the light source.
The higher the luminous efficiency value is, the stronger the lighting equipment's ability to convert electric energy into luminous energy is. Under the same power, the higher the illumination, the higher the brightness.
The unit of luminous efficiency is brightness/watt, sometimes taking the transliteration of Luminance "lumen" and making lumen/watt.
The luminous efficiency is also called the luminous efficiency of the light source or the power factor of the light source. η=φ/E=φ/(φ+P)
Among them, sunlight is the luminous effect, with the light energy radiated by the light source, E is the power of the light source, and P is the energy dissipated by the light source, mainly heat.
And the relationship between heat and current is P is equal to I squared R. Obviously, the luminous flux increases as the current increases. On the other hand, the increase of current will cause the increase of heat loss of the light source.