Flashlights are handy, hand-held devices, which can provide light when the power goes off. They run on batteries. So, for flash bulbs to be useful in times of emergency one needs to store batteries also. Flashlights came into use in the last decade of nineteenth century. At that time, it was used for providing fancy light arrangement. Later some suave businesspersons suddenly realized its potential as a source of light when electric current is not available and marketed flashlights in the form that is found today. In those times, the form of flashlights was very crude. The battery did not have that much charge storage capacity as of today and the bulb consumed more power. As a result, most flash bulbs in those times only provided a flash of light for a short duration and then went dead. Hence, the device got the name “flashlight.” This name got really struck in North America. In other continents, especially in commonwealth countries, it is known as torch light or electric torch.
As already mentioned, the source of energy in most of the flashlights is a battery. It may be normal batteries, rechargeable batteries or solar powered batteries. Even with the technological advances of this age, there is a limit to the amount of power can be stored in the battery that can be fitted into a hand-held flashlight. So the efforts to conserve energy in a flash light have been focusing on reducing the energy utilized by the flash light. Traditionally incandescent bulbs were used as source of light. Such bulbs are still in use. But it has been found that the energy-spending rate of incandescent bulbs is much more than that of some other forms of light source, say light emitting diodes (LEDs). But the problem with LEDs was that the brightness and intensity of light emitted by LEDs were very low comparing to that of fluorescent bulbs. Scientist did extensive research on this subject and conducted numerous experiments to enhance the brightness and intensity of the light produced by LEDs. Finally, they succeeded and a new form of flashlights was born.
There are many advantages LED bulbs have over incandescent lamps. The main advantage in energy conservation is that they utilize less energy than conventional types because they do not contain a filament. LEDs are basically a transistor and work on electronics principles. The life span of LED bulbs is much more than that of incandescent bulbs. LED bulbs can be controlled electronically so as to maintain a fixed level of light intensity irrespective of the amount of power stored in the battery. This is not possible with incandescent lamps. Further experiments aimed at energy conservation in flashlights have led to the advent of self-powered flashlights that do not need a battery and high intensity discharge (HID) flashlights.