Technical Description – Flashlight 

Jayden Garcia 

ENGL 21007: Writing for Engineering 

Professor Julia Brown 

March 20, 2025 

Tabel of Contents 

Definition …………………………………………………………………………………………………………………….. 3 

Overview ……………………………………………………………………………………………………………………… 3 

Components ………………………………………………………………………………………………………………. 4-5 

Explanation ………………………………………………………………………………………………………………….. 6 

Visuals …………………………………………………………………………………………………………………………. 7 

Conclusion …………………………………………………………………………………………………………………… 8 

References ……………………………………………………………………………………………………………………. 9 

Definition: 

The flashlight is a portable, handheld tool that produces light to illuminate dark places and multiple other uses. The history of it spans back all the way to 1899, with English inventor David Misell inventing the first ever flashlight using a dry cell battery and an incandescent bulb. As the years continued, flashlights have started to become better with improvements to batteries, bulbs working differently from each other, and types of flashlights for different environments have been created. This device has become standard in anyone’s household/working environment due to its size and how reliable it is in multiple settings in the world.  

Overview: 

The typical flashlight is shaped like a cylinder, being 3 to 7 inches long and are rather small in size. The housing of the flashlight is made from a mix of plastic and metal and serves as a protective case, so the internals of the device won’t get damaged. At one end, there will be a lens in the front, that is the direction where the light illuminates from. At the other end of the flashlight, some flashlights have a switch called the tail cap, which is used to turn the light on and off, with different tail caps providing different functions ranging from clicking tail caps to momentary activation tail caps. Most flashlights contain both a tail cap and a switch, which is the primary source of turning on the flashlight on the side of it by pressing up or down on it. Additionally, some flashlights come with a clip on it to secure it to pockets, belts and other items. 

Components: 

• Bezel – The ring of the housing which surrounds the lens of the flashlight. The purpose of it is to protect the lens from getting damaged but also holds the purpose of being used as self-defense.  

• Light Source – The source of where the light comes from. The purpose of it being to generate the illumination of the flashlight. In today’s age, most flashlights use LED (Light-Emitting Diode) because they are more energy efficient and last longer.  

• Light Beam – The output of the flashlight. It is a focused beam of light that lightens up your surroundings. Different types of beams can be produced, depending on the design of the flashlight. 

• Reflector – The reflector helps shape and focus the beam, which reflects light from the source. The overall design and material can influence the performance of the flashlight and the beam. 

• Lens – The lens sits in front of the light source and the purpose of it is to further focus and shape the light beam. These lenses can be made from different materials, providing improved properties but can be easily damaged by misuse.  

• Housing – The housing is the outer casing/frame of the flashlight, and it protects all the internal components of the device while providing a sturdy and solid shell. These can be made from various materials like plastic, aluminum and stainless steel. 

• Pocket Clip – The pocket clip lets the user attach the flashlight to their clothes, belt, and other items for easy access to the flashlight. 

• Tail Cap – The tail cap is located at the end of the flashlight and works as a secondary switch to turn on/off the light.  

• Main Switch – The primary switch of the flashlight. Can cycle through different brightness options and come in different designs. 

• The Circuit – Serves as the internal system which powers the light source and manages the functions of the flashlight. If it weren’t for this, all parts would be considered useless. This contains the battery compartment, the driver that regulates power to the LED, and additional wiring for the advanced features.  

Explanation: 

The parts of a flashlight and how they work with each other to make light is interesting. When the main switch is turned on, a flow of electricity starts between two strips, which are powered by the battery. The batteries are connected to run between positive and negative electrodes, resting on a small spring connected to a strip. The strip runs down the battery case and connects with one side of the switch. The other strip on the other side runs to the light source and provides an electrical connection. Additionally, another part is connected to the light source and that contacts the positive electrode of the top battery, finishing the generation of electricity. Once activated via electricity, the light source starts to glow, producing light and reflecting off the reflector. The reflector creates a beam of light from the light source and the lens covers the light source, so the source is not broken. When the switch is turned off, the strips are moved apart and the path to generate electricity is broken, ending the generation of light.  

Visuals: 

Figure 1: Parts of a Flashlight (https://flashlightgo.com/blogs/guide/10-parts-of-a-flashlight-a-beginners-guide-1)  

Figure 2: More parts of a Flashlight (https://flashlightreviews.org/parts-of-a-flashlight/#10_Parts_of_a_Flashlight)  

Conclusion: 

Ever since their introduction to the world, flashlights have always been useful in many ways for many people throughout their lives. However, there are ways that flashlights can cause damage to you or other people. For example, if someone were to shine the light from a flashlight to their own eyes or someone else’s, that can cause temporary blindness if the flashlight is one that uses high-powered LED. Additionally, if the flashlight uses alkaline, lithium or rechargeable batteries, mishandling them can lead to them generating heat and exploding, causing serious injury. Aside from the many issues mishandling a flashlight can cause, they become everyday objects and see uses from multiple settings, making them a staple for everyone.  

References:  

Energizer UK, “How Flashlight Work – Energizer Canada” 

https://energizer.com/canada/about-flashlights/how-does-a-flashlight-work/

Flashlight Battery Safety Guide | Rechargeable and Alkaline | Pelican. (n.d.). Pelican. https://www.pelican.com/us/en/support/flashlight-battery-safety/ 

Watson, L. (2023, August 8). Flashlight Fun! – NIU STEAM. NIU – STEAM. https://niusteam.niu.edu/flashlightfun/#:~:text=Using%20an%20incandescent%20bulb%20and,had%20quite%20a%20few%20upgrades 

Morrison, D. (2022, August 24). 10 parts of a flashlight with diagram: a beginner’s guide. Outlighter. https://flashlightreviews.org/parts-of-a-flashlight/#10_Parts_of_a_Flashlight 

Lee, B. (2024, November 4). 10 Parts of a Flashlight: A Beginner’s Guide. Flashlightgo. https://flashlightgo.com/blogs/guide/10-parts-of-a-flashlight-a-beginners-guide-1