The tube part is the section that holds the different parts of the device, which is called the case.
The bulb is the source of illumination, and is usually either a tungsten filament incandescent bulb or – more commonly in newer models – an LED bulb.
The batteries rest on a small spring that’s connected to two contact strips, which are thin strips of metal – often made of copper or brass – located throughout the device. This makes the electrical connection between the batteries, the lamp and the switch. These parts conduct electricity and complete the circuit.
When the switch is pushed to the ‘on’ position, it begins a flow of electricity powered by the battery.
The reflector part at the front is formed of plastic and coated with a shiny aluminium layer which bends around the bulb, to direct the rays forward so they provide a steady light beam. This is then covered with the lens; a clear plastic at the very front of the device which protects the glass bulb from breaking.
When the switch is pushed into the ‘off’ position, the contact strips are moved apart and the path for the electrical current is broken, which stops the device producing light.