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Classification of Lamps

Incandescent LampsIn these the light comes from a heated metal wire. The halogen

lamp contain a special gas to improve the efficiency.These types are widely used but will bephased out in the coming years due to their low efficiency

Gas Discharge Lamps:

 The Light from these comes from a discharge between two electrodes from a discharge between

two electrodes in a gas filled gas or ceramic tube.

Solid State Lighting or L.E.D Lamps

An LED is a semiconductor device. When a current is passed through a LED, electronics movethrough the semiconductor material and some of them fall into a lower energy state. In theprocess the spare energy is emitted as light.

Incandescent Lamps

How Incandescent Lamps Work 

The word incandescent means emitting visible radiation from solid material as the resultof being heated. Below figure shows that an incandescent lamp produces light from alength of heated wire. The wire temperature can be as high as 2800 degrees Celsius.The wire is called a filament and is normally in the shape of a coil. The wire is made of tungsten because of its very high melting point.

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Lamp Parts When exposed to surrounding air, the heated filament literally burns up and

disintegrates in a short time. This is solved by enclosing the filament in a glass envelopeor BULB. Air is removed from inside the bulb at the time of manufacture to form avacuum, or the bulb is filled with an inert gas usually a mixture of nitrogen and argon.

The LAMP CAP connects the lamp to the electrical circuit made of aluminium or brass.

FILAMENT SUPPORTS are wires that hold the filament in place - protect it duringshipment and in service.

LEAD WIRES are the internal wires that connect the filament to the lamp cap.

BUTTON is the top of central glass stem which holds the filament support wires.

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HEAT DEFLECTING DISC (not shown) reduces the flow of hot gases from around thefilament into the neck of the bulb protects the stem and cap - usually only found in lampsof more than 250W.

PINCH is where the entry of the lead wires into the glass bulb are sealed.

EXHAUST TUBE is connected to a hole in the pinch and is where the air is removed andthe bulb filled with gas during manufacture.

FUSE is a protective device as part of the lead wire in case an arc or short circuitdevelops inside the lamp.

Incandescent Lamp Advantages 

Incandescent lamps offer a number of advantages:

1. Simple to use - direct connection into socket.2. Lowest initial lamp cost.3. Immediate starting and re-starting - no warm-up or cool down required.4. Excellent optical control - concentrated light source is easiest to direct or focus.5. Easiest to dim - simple variable resistor circuitry may be all that is required.6. Wide design flexibility - variety of styles, outputs, and colours fill nearly every

need.7. Output not affected by operation over a wide range of ambient temperature.8. Available in wattage ratings from 10 to 100W.

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  Q & A Incandescent Lamps

1. The filament of an incandescent lamp is made from carbon, tungsten or steel?

2. The inside of an incandescent light bulb has all the air removed and then can be filledwithnitrogen and oxygen mixturenitrogen and hydrogen mixturenitrogen and argon mixture

3. Name the parts indicated on the following drawing.

a.

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4. Give the reasons why coiled coil filaments areused. ........................................... ...........................................

5. What type of lamp should be used when it is likely to be exposed to somevibration? ..................................................

6. Describe the filament construction for Rough Servicelamps. ..................................................

7. The coating of reflector lamps is of:a. silver 

tungstenaluminium

8. Incandescent lamps have a colour rendering index (Ra) of .............

9. List five advantages of incandescentlamps. ......................................... ......................................... ......................................... ......................................... .........................................

10. Lamp efficacy is measured in lumens per watt, which is important because it affectsthe .....................................................of lighting.

11. Is it possible to use incandescent lams on continuous current ( dc-voltage )?

12. What's the regarding standard of security for incandescent lamps?

13. Does it affect service life when you frequently switch incandescent lamps?

 

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