A flashlight (US) or torch (UK) is a portable hand-held electric light. The source of the light often used to be an incandescent light bulb (lamp) but has been gradually replaced by light-emitting diodes (LEDs) since the mid-2000s. A typical flashlight consists of the light source mounted in a reflector, a transparent cover (sometimes combined with a lens) to protect the light source and reflector, a battery, and a switch. These are supported and protected by a case.
The invention of the dry cell and miniature incandescent electric lamps made the first battery-powered flashlights possible around 1899. Today, flashlights use mostly light-emitting diodes and run on disposable or rechargeable batteries. Some are powered by the user turning a crank, shaking the lamp, or squeezing it. Some have solar panels to recharge the battery.
In addition to the general-purpose hand-held flashlight, many forms have been adapted for special uses. Head or helmet-mounted flashlights designed for miners and campers leave the hands free. Some flashlights can be used underwater or in flammable atmospheres. Flashlights are used as a light source when in a place without electrical outlets, during power outages or when light is needed in a place where a wired lamp is difficult to use, for example, behind or underneath heavy furniture or when servicing appliances.
Last updated on 2021年03月23日
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