Electricity and Circuit Notes

WORKING OF AN ELECTRIC BULB

•    In a transparent electric bulb, there is a thin filament or a very thin metal wire. The filament heats up when an electric current is passed through it. It heats up so much that it begins to glow and gives out light.

•    In case a very large current flows through the bulb the filament gets heated up too much and gets broken, the bulb is said to be fused. Such a bulb cannot give light as the path is not available for current to flow.
 

Invention of electric bulb:

•    The first electric bulb was made in 1809 by Humphry Davy, then It was perfected by Thomas Alva Edison.

•    In 1910, William David Coolidge invented a tungsten filament which lasted even longer than the older filaments.
 

SOURCES OF ELECTRIC CURRENT

•    A device that can be used to produce an electric current is called a source of electric current

•    Common sources of electric current are cells and batteries (collection of cells) of various shapes and sizes.

•    Electricity generated on large scale by Thermal Power Plants and Hydroelectric Power Plants is supplied to our homes and offices.

Thermal power station:      

COMMON SOURCES OF ELECTRIC CURRENT

•    Cells and batteries of different shapes and sizes are common sources of electric current.

Cells:

•    They convert chemical energy into electrical energy.

Cells are of Two Types:

Primary cell: