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What is an electric lamp and incandescent lamp ?


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What is an electric lamp?

An electric lamp is a gllas bulb, often filled with nitrogen or some other chemically inactive gas containing a wire or filament usually made of tungsten in which the passage of an electric current through the filament heats it to a white heat and then to the visible radiation i.e. light.

What are the types of lamps ?

There are types of lamps for producing light by electricity. Incandescent lamp, b) Electric arc lamp and c) Gas discharge lamp.

What do you mean by incandescent lamp ?

The incandescent or filament type consists of a file metallic wire of high resistance known as filament enclosed in an evacuated glass globe. When the electric current passes through the filament, heat is produced and the temperature of the filament increases. At high temperature, it radiates heat as well as light energy thereby producing electric lights by incandescence of a heated filament.

What are the types of incandescent lamps?

The two types of incandescent lamps are - (a) Metal filament lamps & (b) Carbon filament lamps.

What should be the properties of metal as a filament in the incandescent lamp ?

It should have high melting point, low vapour pressure, high resistivity and low-temperature coefficient. It should be ductile and mechanically very strong to withstand vibrations during normal use.

Which materials are used for the filament of the incandescent lamps ?

Tungsten, Tantalum and Carbon.

Which material is mostly used for the filament of incandescent lamps and why ?

Tungsten is widely used for the filament of the incandescent lamp due to its high-temperature co-efficient, high melting point, low vapour pressure, ductility and good mechanical strength.

What are the melting point and working temperature of the tungsten filament?

Melting point is 3400°C and working temperature is about 2000°C.

What are the types of filaments normally used?

(a) Straight wire type, (b) Coiled type and (c) Coiled-coil type.

Why are the modern incandescent lamps made of coiled filament?

The causes are as follows :-

  1. Coiled coil filament is mechanically stronger.
  2. It can operate at high temperature.
  3. It gives greater output.
  4. It gives greater efficiency.

On which principle does the incandescent lamp work?

Incandescent lamp works by the heating effect of electricity.


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