Page 184 - Green Butterfly Book 2

Date:
unit 9
4. Extension to Science
How Does a Light Bulb Work?
There are some things that we are so used to have that we do not even think there was a time where they did not exist. The perfect example is turning on the lights whenever we need them; if we are studying for an exam at night we can turn on a lamp and we can continue reading. Imagine shopping at a mall and not having any light!
Can you imagine having to use candles or gas lamps all the time? As you read in the story, there was a time when they did just that.
But, do you know how a light bulb works?
The key is electricity which can make special types of metals heat up and when those metals get very hot, they start to light up.
Electricity runs through a thin wire called
“filament” which is inside the light bulb, as
the filament becomes hot it lights up. If you look carefully at a light bulb you can see this tiny, thin metal coil at the center of the bulb. The filament inside may look very small, but when it heats up, it gives off plenty of light. Edison’s light bulb used carbonized cotton thread but they were later replaced by tungsten.
The base contains two metal contacts, which connect to the filament. When you turn on the light switch, you are sending an electric current from the switch to the bulb.
The glass of the light bulb does more than protect the filament from burning anything, it also helps to keep the air out which can cause combustion and make
unit
Mixture of inert gasses at low pressure
Coiled tungsten filament
Glass fuse enclosure
Screw cap
Glass envelope
Support wires
Connecting wires
Electrical contact
Light Bulb
9
182