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 ……………………………………………………………………………………………………………………… 7-8 

Conclusion ………………………………………………………………………………………………………………… 8-9 

References ………………………………………………………………………………………………………………….. 10 

Definition: 

The flashlight is a portable, handheld tool that produces light to illuminate dark places and multiple other uses. The purpose of it is to be used as a light source you can take with you anywhere you travel. 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, with one end of it being where the light comes out of. The average length of a flashlight is 3 to 7 inches long and varying in size to allow for everyday carry. The housing of the flashlight is made from a mix of plastic and metal, differing in color which serves no purpose. As for weight, they vary from 4-12 ounces for smaller flashlights to 2-5 pounds for the more powerful ones. 

Components: 

• Bezel – The ring of the housing which surrounds the lens of the flashlight. Its purpose is to protect the lens from getting damaged or scratched from uses and help with focusing the beam of light from the flashlight (Bruce Lee, 2024).  

• Light Source – The source of where the light comes from. The purpose of it being to generate the illumination of the flashlight. Modern flashlights use LED (Light-Emitting Diode) because they are more energy efficient and last longer (Lee, 2024).  

• 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 like a broad beam to light up areas in a short distance or focused beam to illuminate an object from far (Knivesandtools, 2020). These depend 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 (Lee, 2024). 

• 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 like borosilicate glass being the popular choice, sapphire glass and other types of glass can be used, providing improved properties but can be easily damaged by misuse (hylasercutting, 2023).  

• 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 (Dillon Morrison, 2023). 

• Pocket Clip – The pocket clip lets the user attach the flashlight to their clothes, belt, and other items for easy access to the flashlight (Lee, 2024). 

• 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 (Lee, 2024).  

• Main Switch – The primary switch of the flashlight. Can cycle through different brightness options and come in different designs (Morrison, 2023). 

• 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 (Lee, 2024).  

Explanation: 

When the main switch of a flashlight 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 (Energizer UK). 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 (Energizer UK). 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)  

Figure 3: Flashlight Circuit (https://stock.adobe.com/images/electric-circuit-scheme-diagram-how-to-light-a-bulb-opened-closed-switch-torch-parts-explanations-electricity-sample-battery-conductor-wire-electrical-current-board-black-background-vector/622062154)   

Conclusion: 

The history of the flashlight 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 (Lindsay Van Geem, 2022). This discovery led to drastic improvements in quality for users so the flashlight can be safer to use. However, there are still 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 (Pelican, 2019). 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/ 

Geem, 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 

“Light beam, light source, light image? Knivesandtools explains.” Knivesandtools, 21 Jan. 2020, www.knivesandtools.com/en/ct/lightbeam-lightsource-lightimage.htm. 

“Exploring the Best Glass Materials for Flashlight Lenses.” OEM Custom Sapphire Glass & Optics Parts Manufacturer, 8 July 2023,  Client Challenge.  

https://hylasercutting.com/exploring-the-best-glass-materials-for-flashlight-lenses/#:~:text=Borosilicate%20glass%20is%20a%20popular,it%20resistant%20to%20thermal%20shocks

https://stock.adobe.com/images/electric-circuit-scheme-diagram-how-to-light-a-bulb-opened-closed-switch-torch-parts-explanations-electricity-sample-battery-conductor-wire-electrical-current-board-black-background-vector/622062154