Static Electricity PVC Pipe (Erica Brauer)
Author
Erica Brauer
Principle(s) Illustrated
When two different materials come into close contact, for example, felt rubbing against a balloon or two air masses in a storm cloud, electrons may be transferred from one material to the other. When this happens, one material ends up with an excess of electrons and becomes negatively charged, while the other ends up with a deficiency of electrons and becomes positively charged. This accumulation of imbalanced charges on objects results in the phenomena we commonly refer to as static electricity.
Electrostatic Force
Standards
NGSS SEP: Asking questions
NGSS CCC: Structure and Function
NGSS DCI: PS1.A Structure and properties of matter
Topic: Atomic structure & Types of interactions
Questioning Script
Prior knowledge & experience:
Students should know about the structure of an atom, positive protons in the middle and negative electrons orbiting around the nucleus
Root question:
1. What will happen to the balloons when the PVC gets near it?
2. What will happen to the top plate?
Target response:
Electrons may be transferred from one material to the other. When this happens, one material ends up with an excess of electrons and becomes negatively charged, while the other ends up with a deficiency of electrons and becomes positively charged.
Common Misconceptions:
They might think it is electromagnetic and will repel one side of the PVC pipe and attract the other.
Practical Applications:
Pollution Control
Static electricity is used in pollution control by applying a static charge to dirt particles in the air and then collecting those charged particles on a plate or collector of the opposite electrical charge. Such devices are often called electrostatic precipitators.
Factories use static electricity to reduce pollution coming from their smokestacks. They give the smoke an electric charge. When it passes by electrodes of the opposite charge, most of the smoke particles cling to the electrodes. This keeps the pollution from going out into the atmosphere.
The Photocopier
One example of the practical use of static electricity is a photocopier. A photocopier is a complicated piece of equipment, but the basic principle of how it works is fairly simple. The best way to understand what is going on is to consider it as a stage by stage process.
Stage 1
Stage 2
Stage 3
Stage 4
Stage one
Positive charge is sprayed onto a plate from a high voltage power supply which is called charging by friction. The plate is connected to the earth but the charge does not have quite enough energy to flow away from it. (The plate is not a good conductor of electricity.)
Stage two
Paper is placed over the plate and a light shone onto the paper. Where the paper is white the light is reflected onto the plate. Where the paper is dark a shadow falls onto the plate. The light falling on the plate gives it just the extra energy needed to allow the charge to escape to earth. The plate becomes neutral where the paper is white but keeps its charge where the paper is black. The plate is now a copy of the paper with charges taking the place of ink. You could call this a template.
Stage three
Toner particles are sprayed through a negatively charged nozzle onto the plate. As the toner passes through the nozzle it picks up the charge so that each particle of toner becomes negatively charged. The now charged toner is attracted to the areas of positive charge because unlike charges attract. More light then allows the positive charge to escape (However the negative charge on the toner remains.)
Stage four
A sheet of paper is given a very strong positive charge, and then placed in contact with the plate. The paper attracts the toner. The paper is then removed from the plate and passed through a heating unit. The heat melts the toner and bonds it to the paper.
In a real photocopier, there is no plate, just a large drum. As the drum rotates its surface goes through stages one through four. At the end of the sequence a scraper removes any toner left on the drum and the whole process is repeated with a new image. A good photocopier is capable of producing 20 duplicate pages per minute (20ppm), which is approximately one page every three seconds.