How does a flashlight work?

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Update time : 2020-09-25 16:10:35

What is a flashlight?


A flashlight is a small battery-operated portable electric light, which is called a torch in some English-speaking countries other than the US.





Throughout history, human beings have been in need of light sources which can move with them. Firebrand and candles were early illumination tools but were largely replaced by oil lamps and kerosene lamps as science develops. However, all these methods are potentially dangerous because they have a flame.


The first dry cell battery was manufactured by the National Carbon Company in 1896 after German physician Carl Gassner invented it in 1888. It’s a type of electric battery which was an improved version of its predecessor, as its electrolyte was a paste instead of a liquid.

Thanks to this, it could work in any position and wouldn’t break or spill as easily – making it ideal for a portable light source. So in 1899, British inventor David Misell developed the first flashlight model.



Torch or Flashlight


Before the flashlight was invented in the 1890s, the word “torch” was described as a stick that could be lit and used as a light source. When flashlights were commonly used in the world, they were originally called electric torches in the UK. Later, “electric” was left out because it became a synonym for flashlights that Americans used.


Why was this device originally named “flashlight”? Because the zinc-carbon batteries which powered it cannot offer constant current for a long run time, that means, it had to be turned off. Russian inventor Conrad Hubert gave it this name. He was the person who brought Misell’s invention to market.


However, some people are arguing this because they think the modern flashlights can last for a long time without “flash” and no need to be turned off any longer, so “flash” should not be used.


Main Part of Flashlights



The tube that houses the parts of the flashlight, including the batteries and lamp (light bulb). Some are plastic made, while some are metal, including aluminum, titanium, copper, stainless steel and etc.



LED is the light source of the flashlight. In the past, it was tungsten filament incandescent bulbs. But nowadays, it is more commonly LED bulbs. FREASYGEARS mostly uses CREE LEDs which have an amazing lifespan as long as 50,000 to 100,000 hours. Visible light would be produced when electricity flows through it and glows.


Reflector and Lens


The reflector redirects the light rays from the lamp, creating a steady beam of light, which is the light you see emitting from the flashlight. There are 2 kinds of reflectors - smooth and orange peel. The smooth reflectors produce the best "throw" or furthest distance the beam is seen at, but also show more imperfections in the beam pattern, which is usually only really noticed while white wall hunting at home. The orange peel reflectors disperse the beam a little more to offer better flood but don't offer as much throw.


The clear part on the front of the flashlight is called a lens, which is to protect the glass bulb from breaking.




The switch is the channel of human-machine dialogue. There are many kinds of switches in the market now, such as push-button switches, rotary switches, and electronic switches. Push-button switches are divided into forward and reverse switches. The so-called forward switch is a tap-and-shoot which is also known as a tactical switch (tactical flashlight CYANSKY P25). To offer more convenience for using, many flashlights manufacturers design not just one switch now, instead, two or even three switches become more and more common.




The circuit is also very important. It is one of the key factors impacting the safety and reliability of the torches. The circuit and LED are the resolution factors for the innate brightness of the flashlight without thinking about the battery. Cheap lights may also reach high lumen, but they seldom consider the stability and protection for other parts such as LED. Instead, the circuit that most top-quality flashlights use often includes output levels management system, low standby current system, overcharge and over-discharge protection, short circuit protection and etc. Thus, the light can not only reach high lumen but also keep safe, reliable, stable, and highly efficient.


Positive and negative springs or contacts

The contact is a very thin spring or strip of metal, which is to connect the battery, lamp, and switch electrically. The first function is conductivity. The smaller the internal resistance, the better. Thus, the spring is usually copper or brass. The other key effect is shock absorption, which can avoid bad touch and shifting. This is extremely important for hunting flashlights or pistol lights.



The battery is the source power of torches. There are mainly four types of batteries - Li-ion Rechargeable Batteries, Nickel-Metal Hydride (NiMH) Rechargeable Batteries, Lithium (NOT Lithium-Ion) Non-Rechargeable Batteries, and Alkaline Non-Rechargeable Batteries.



How do the parts of a flashlight work together to create light?


When the switch of a flashlight is pushed into the ON position, it makes contact between two contact strips, which begin a steady flow of electricity. These contacts are connected to the spring at the bottom of the battery, and the spring is connected to the battery, allowing electricity to flow from the battery positive terminal throughout the lamp and back to the battery negative terminal. This exchange of electricity would make the bulb or LED glow. When the switch is pushed into the OFF position, the contact strips would be physically separated and the electric current pathway would be broken and turn the light off.

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