Whether you're camping in the woods or need to find your way around the house after a power outage, a flashlight is essential. These tools are often indispensible in emergency situations, as they provide a portable light source. Most flashlights are made to be handheld devices, but some can be mounted, for example, on the helmets of miners or on bicycles so the user can see more easily in the dark and keep their hands free. No matter how technologically advanced the world may get, simple flashlights are still important to have on hand for a variety of different situations, and it's a good idea to become familiar with the basics of flashlights in order to choose one that suits your needs.
Flashlights are built around a light source that is mounted into a protective case and attached to a reflecting device. In most cases, the reflecting device is a lens made of transparent material. Batteries are the typical power source for flashlights. A switch on the body of the flashlight activates the light source. Some flashlights can recharge themselves, using solar power; some use cranks, magnetic fields and rechargeable battery cells for this purpose.
Some flashlights use incandescent bulbs as a light source. Others use LED (light-emitting diode) or HID (high intensity discharge) lights. The differences in light sources determine how much light the flashlight gives off, and how efficient it is. An incandescent bulb is less efficient than LEDs or HIDs, and as a result, uses batteries up faster. The LED flashlight also produces not only light but also warmth. HID flashlights are less fragile and are better able to absorb shocks if they are dropped. They are more expensive, however, because of the extensive circuitry needed to keep the light source operating.