How a photocopier works :: essays research papers

Photocopiers rely on static electricity to perform an incredibly complex process every time you press the copy button. Photocopiers use a photo receptor drum, a metal drum coated in a layer of semiconductor which is usually selenium. The photoconductivity of selenium means that when illuminated photons cause it to conduct electricity but when it is in the dark it is an insulator. When photons hit the Selenium electrons are liberated allowing current to pass through. When you press COPY on a photocopier a complex process begins. The drum is charged positively by the corona wire; this wire has a very high voltage passed through it and so transfers some to the drum as static electricity. The drum is coated in a layer of positive ions. A strong lamp is then shone up through glass onto the paper which needs to be photocopied. White areas of paper reflect this light back down, through a series of mirrors and lenses, onto the drum. Black areas (print) just absorb the light. When the light hits the selenium it allows current to flow by liberating electrons, the electrons brought by this voltage applied to the core of the drum neutralise the positive charge on parts of the drum in light so that only black areas are now charged. Next small beads covered in tiny black plastic powder are rolled over the drum. The powder is attracted to the drum at areas of positive charge because the toner is negatively charged. Another sheet of paper is charged strongly by the corona wire because this charge is greater than the charge on the drum, when the paper is passed over the drum the toner particles stick to it rather than the drum. When the paper has the toner on it, it passes through heated rollers which melt the black plastic onto the paper so that it is not held with just a weak charge. How a photocopier works :: essays research papers Photocopiers rely on static electricity to perform an incredibly complex process every time you press the copy button. Photocopiers use a photo receptor drum, a metal drum coated in a layer of semiconductor which is usually selenium. The photoconductivity of selenium means that when illuminated photons cause it to conduct electricity but when it is in the dark it is an insulator. When photons hit the Selenium electrons are liberated allowing current to pass through. When you press COPY on a photocopier a complex process begins. The drum is charged positively by the corona wire; this wire has a very high voltage passed through it and so transfers some to the drum as static electricity. The drum is coated in a layer of positive ions. A strong lamp is then shone up through glass onto the paper which needs to be photocopied. White areas of paper reflect this light back down, through a series of mirrors and lenses, onto the drum. Black areas (print) just absorb the light. When the light hits the selenium it allows current to flow by liberating electrons, the electrons brought by this voltage applied to the core of the drum neutralise the positive charge on parts of the drum in light so that only black areas are now charged. Next small beads covered in tiny black plastic powder are rolled over the drum. The powder is attracted to the drum at areas of positive charge because the toner is negatively charged. Another sheet of paper is charged strongly by the corona wire because this charge is greater than the charge on the drum, when the paper is passed over the drum the toner particles stick to it rather than the drum. When the paper has the toner on it, it passes through heated rollers which melt the black plastic onto the paper so that it is not held with just a weak charge.