Light Bulb
From DT Online
Bulbs are used as a form of illumination or indication and the type commonly used has a filament coil which glows white hot when a current passes through it. The filament is in a space filled with an inert gas to aid light output and to prevent oxidisation of the filament
Bulbs consume more power than LEDs but give a high light output. There are two common types of bulb used in schools MES and LES - which are smaller in physical size than MES types. They may be bayonet or screw cap but screw types are more common.
The voltage and current rating is usually stamped on the side of the body of the bulb. The voltage rating of bulbs in normal use are 2.5, 3.5, 6 and 12V. The correct voltage rating must be used although there is a certain amount of leeway. For example a 6V bulb could be run from a 4.5 volt battery but with reduced light output. Also a 6 volt battery could run a 3.5V bulb causing it to glow brighter and with likely shorter life.
The current rating on the bulb determines the amount of current the bulb will draw used at its correct voltage rating. The higher the current the brighter the bulb will glow (and shorter the battery life will be). Clear glass bulbs are the most common but coloured glasses are available as are flashing bulbs but at a higher cost. Bulbs are usually screwed into a bulb holder which incorporates terminals for connecting wires and to aid in the physical mounting.