THE gas-filled lamp has now largely superseded the vacuum lamp, as it emits a whiter light and is more efficient: that is, gives more light proportionately to the electrical energy used.

The bulb, after being exhausted of air during manufacture, is filled to half atmospheric pressure with a gas called argon, which is unable to attack the filament. The last can therefore be raised to a greater heat than would be safe in a vacuum lamp. So intense is the illumination that the bulbs of gas-filled lamps are usually frosted, to scatter the light and protect the eyes from the direct glare of the filament.

Lamps are rated in watts according to the energy they consume: 40 watts, 60 W&ttS, 100 watts, and so on. On every lamp will be found engraved the pressure in volts of the supply for which the lamp is suitable, and the watts needed to run it; for example, 240V – 40W.

For the good general illumination of a room what is called semi-indirect lighting is now much used. A powerful lamp, say one of 100 watts, is suspended 8 or 9 feet above the floor at the centre of the room, inside a frosted or semi-transparent bowl. Some of the light comes through the bowl, but most of it is reflected from the ceiling.

Bulbs should be kept clean outside.

Dust and fly marks can reduce their efficiency very considerably.

Enhanced by Zemanta