A flashlight, also called a torch is a portable device used for illumination and usually has battery cells for power. A flashlight usually consists of a small electric light bulb, a compartment for batteries which power the bulb, a switch for the bulb and a parabolic reflector for focusing the light. The battery compartment also acts like a handle for holding the flashlight.
Though the flashlight is of a very simple design, it is a relatively new invention. It came into being after the incandescent light bulb and the dry cell was invented.
The name “flashlight” has a humorous background. In the early days of the dry cell, the power of a dry cell battery was very limited. To save the dry cell from discharging quickly, the flashlight was operated intermittently and just long enough to check out the environments, hence the name “flashlight”.
There are many flashlight designs available in the market today. Like dry cell flash lights, rechargeable acid type flashlights, rechargeable dry cell type, LED (Light Emitting Diode) type, solar charging type, electromagnet type, head lamp type, underwater type, rifle or gun light etc.
The dry cell flashlight is the simplest design and used in most households and consists of dry cells to power the electric bulb. As the batteries discharge the illumination dims in these flashlights.
Rather than buying a flashlight, which needs battery replacement frequently, a better design is to use rechargeable batteries, which can be lead acid type or dry cell type.
Some use solar panels for recharging during daytime. Electromagnet type uses a clockwork arrangement or a knob arrangement. In clockwork arrangement a spring mechanism is used to power the flashlight and has to be wound as required. The knob type arrangement has a moving coil or magnet which moves when the knob is pressed and charges a capacitor, which provides power to the bulb.
LED type flashlights are of a recent design. Though LED:s have been around for decades, the LED flashlight was not available till late 90s because the LED:s could not be operated continuously and their luminosity was very poor.
LED flashlights consume very little power compared to the conventional electric bulb as LED:s do not produce as much heat as electric bulb. LED flashlights usually have a metal body to dissipate heat by conduction since LED:s do not dissipate heat through the light beam like electric bulbs do.
A headlamp type has a flashlight on a helmet so that the hands are free. Underwater type is a special flashlight, which is used for illuminating underwater objects and is waterproof. Rifle or gun lights are special flashlights used for illumination of target.
Flashlights are fairly cheap and available in attractive designs. The price ranges from a few dollars to a couple of hundred dollars.