The which the original document is place

The working of photocopier is based on the principle of photoconductivity and
Coulomb’s law. Photoconductivity is a property by virtue of which substance like carbon
sulphide, and selenium conduct when light is incident on then and Coulomb’s law states that like
charges repel and unlike charges attract.
The photocopier is consist of aluminium drum (photosensitive drum) which surface is
slightly oxidized and over the oxidized surface there is a thin layer of selenium which is a
photosensitive material. This drum is enclosed in a completely dark compartment, but there is a
fine slit for the entry of light. There is a transparent glass which the original document is place
and it should have in contact with the transparent glass. The optical system which focus the light
is composed of mirrors, and a lens. The developing tank is composed of magnetic brush roller,
and a toner box. The toner is composed of special black substance that melts on heating and the
carrier is composed of tiny beads and the mixture of toner and carrier beads is called developer
and the heating chamber helps fixing the toner into the paper.When you place document to be copied
on the transparent glass and press the start
button a beam of light scans though to it from
up to bottom. Then this light is being reflected
to the aluminium drum which is a
photosensitive material which is electro
statically charged by a high voltage wire called
the corona wire. As already stated that the
surface of it is slightly oxidized and over the
oxidized surface there is a thin layer ofselenium which is a photosensitive material which is a semiconductor so it can act as an insulator
in dark areas and when light falls on it, it
conducts electricity (Photoconductivity). As the
beam of light scan the document the light from
the white part got reflected, and the light from
the dark area do not reflect. As this reflected
light falls on the photosensitive drum, the areas
of photoconductor which was exposed to light
becomes conductive and gets discharge
whereas the area of the drum which was not
exposed to light remains negatively charge. As
the photosensitive drum rotates, it carries
electrical shadow towards the toner. The toner
is a positively charge, so it sticks to the electrical shadow which is negatively charge (Coulomb’s
law). Which means the ink image is formed on the drum. Then the paper is feed up, as it moves
along the paper is given a strong electrical charge which results that the toner image is
transferred from the surface of the drum to the paper. Then this paper is passed through the
heating chamber, the heat and pressure from the two rollers of it permanently fuses the toner
particles on the paper, by that the paper is feel warm and smooth.