Electric Lamp | Types of Electric Lamp

An electric lamp is defined as a component used in circuits for lighting and indicating purposes. Its simple construction includes a tungsten filament inside a transparent glass cover. The tungsten filament glows without melting when current flows through it because of its high melting point.

Uses of Electric Lamps

These lamps are mainly get used for lighting and indicating purpose. Although, now a days use of light emitting diodes LEDs for these two purposes dominates uses of conventional lamps. But still they are in use although at maximum places they are replaced by LEDs.

Rating of Electric Lamps

There are mainly three things that must be known before selecting a lamp for a specific purpose.

1. The Voltage rating of an electric lamp indicates the voltage needed for the lamp to emit normal brightness. This rating is marked on the lamp. If the voltage is too low, the lamp won’t glow properly. If it’s too high, the filament might burn out.
2. Power Rating or Current Rating of Electric Lamp:
   When an electric lamp is connected to its rated voltage, the filament carries current based on its electrical resistance. The filament is designed to give optimal brightness at this current. The current rating is important because it determines the lamp’s power consumption, calculated as the product of voltage and current.
   

   Hence, if voltage rating of a lamp is known to us, then it is enough to know either current rating or power rating of that lamp, as power rating can be calculated from current rating and current rating can be calculated from power rating since electric power is product of voltage and current. It is normal practice that small rated lamps are rated by current and higher rated electric lamps are rated by power.

   
   

Types of Electric Lamps

Another thing must be considered during selecting a lamp for a circuit. What types of an electric lamp is suitable for specific circuits? Types of lamp depend upon designing pattern of the lamps. According to variation of designs, there are varieties of types lamps are listed below,

Edison Screw type Lamps

The main feature of this type of lamp is that it has one contact in the base and other contact on the metallic body of the lamp. This metallic body of the lamp is of screw shaped. Commonly two types of Edison Screw lamps are available in market –

1. Miniature Edison Screw Lamp (MES) its bulb diameter is 10 mm (approx).
2. Lilliput Edison Screw Lamp (LES) its bulb diameter is 5 mm (approx).

Miniature Center Contact type Lamps

Like MES and LES, it has one contact in the base and other contact on the metallic body of the lamp. But main difference is that this metallic body of the lamp is not screw shaped-it has bayonet style fittings. Its bulb diameter is 10 mm (approx).

Small Bayonet Cap Lamps

It has also bayonet style fitting but has both contacts on the base of the lamp, hence there is no electrical connection with the body of the lamp. The standard bulb diameter is about 40 mm. It may have horizontal as well as vertical filament arrangements as shown. The power rating of the bulb can be up to 24 watt.

Wire Ended Lamps

Wire Ended Lamps are very small, about 6 mm long and 3 mm in diameter. They have a simple design with contact wires coming directly out of the glass casing. These lamps are designed for low power and are inexpensive. They don’t need a lamp holder and can be soldered directly to circuit boards.