HOW DO PHOTOCOPIERS WORK?

Let’s start with something simple. I am sure many of you have rubbed a balloon or a comb on your hair or sweater and seen little bits of paper attracted to it. Surprise! The physics behind both phenomenon is the same. It’s called ELECTROSTATICS.

Let’s see what happens when you rub a balloon on your hair or a wool sweater. 

• Electron transfer – Rubbing the balloon creates friction, which causes electrons to be transferred from your hair (or the sweater) to the balloon. As a result, the balloon becomes negatively charged (gains electrons), while your hair loses electrons and becomes positively charged.
• Static Charge – The balloon now has an excess of negative charges, and your hair has a deficit of electrons, creating an opposite charge between the two.
• Attraction and Repulsion – If you bring the charged balloon close to another object with an opposite charge, they will attract each other. This difference in charge leads to attraction; the negatively charged balloon can attract lightweight objects like small bits of paper or even your hair. If you bring two negatively charged balloons close together, they will repel each other, demonstrating the basic PRINCIPLES OF ELECTROSTATICS.

Photocopiers utilize similar electrostatic principles to create copies of documents:

1. Charging the Drum: The photocopier has a photosensitive drum that is uniformly charged using a high-voltage wire (corona wire), giving it a positive charge, similar to how the balloon becomes charged.
2. Image Formation: When you place a document on the copier, a bright light scans it. The light reflects off the white areas of the document and exposes the drum. The exposed areas lose their charge, creating a latent image where the dark areas remain charged. So only the dark areas remain with positive charge.
3. Toner Attraction: Toner, which is negatively charged, is applied to the drum. The toner sticks to the positively charged areas (the dark parts of the image) due to the attraction between opposite charges. This is similar to how the negatively charged balloon attracts lightweight objects.
4. Transfer to Paper: The paper then moves into contact with the drum. The toner transfers from the drum to the paper based on the static charges, ensuring the image is applied correctly.
5. Fusing: Finally, the paper passes through a fuser that uses heat and pressure to permanently bond the toner to the paper, making the copy durable.

By understanding the balloon example, you can see how basic electrostatic principles apply to the technology in photocopiers. Both processes demonstrate the fascinating interaction of electric charges, showing how science plays a crucial role in everyday life!

Fun fact about ELECTROSTATICS: Did you know that phone touchscreens and air purifiers use the same principle of electrostatics?