The electric torch or flash light

    A flash light or an electric torch is a hand-held, portable, electrically-powered light source.

    It is commonly used for finding keyholes, supplementing dark-adapted vision, or helping you find your way when walking in the dark.

    The electric torch was invented in 1902 by Conrad Hubert, who was also known as Akiba Horowitz. 

    A typical flashlight consists of a light bulb mounted  in a reflector with a transparent cover to protect the light source and reflector, a battery, and a switch. These are supported and protected by a plastic case.

    The central part of a torch is the battery. The bottom of the bulb rests on the positive terminal of the battery. The zinc case of the battery forms the negative terminal. The negative terminal of the battery is connected to the switch by a brass strip. Another brass strip runs from the switch to the metal case of the bulb.

    The bulb contains a very thin wire called a filament. The filament, made of a tungsten alloy, is enclosed in a vacuum. The filament rests on two glass columns. Two wires pass through the columns and the whole assembly is enclosed in a thin glass envelope. 

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