A Then a blank sheet of paper is feed

A photocopier machine has the following important components: a halogen lamp,
a photo sensitive drum, a toner, and a conveyor belt for loading blank papers. According
to Woodford (2017), when you place the document you want to be copied upside down
on the glass and press the start button, an intense beam of light from the halogen lamp
scans across the document from top to bottom. This light then gets reflected and falls on
the photo sensitive drum. This photo sensitive drum is a metal roller which is
electrostatically charged by a high voltage wire called the corona wire. This metal drum
is coated with photo sensitive chemical called selenium. It is a semiconductor. So it has
the property to act as an insulator in dark areas and when light falls on it, it conducts
electricity. Now when the beam of light scans across the document, light got reflected
from the white areas (where there is no ink), whereas printed letters being black, did not
reflect any light. When this reflected light falls on the photo sensitive drum, the areas of
the photo-conductor which was exposed to light becomes conductive and gets
discharged, whereas the areas of the drum which was not exposed to light remains
negatively charged. Thus we get an “electrical shadow” of the page on the photo sensitive
drum. Further, as the photo sensitive drum rotates, it carries this electrical shadow
towards the toner. The toner is positively charged, so it sticks to the electrical shadow
which is negatively charged. Thus an inked image of the document is formed on the drum.
Then a blank sheet of paper is feed up from the hopper, as it moves along, the paper is
given a strong electrical charge. With this, the toner image is transferred from the surface
of the drum onto a piece of paper. This paper then passes through two hot rollers. The
heat and pressure from rollers permanently fuses the toner particles on the paper. This explains why the photocopied paper feels warm when taken out from the machine.


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