Static electricity was known to people more than 2500 years ago. The Greeks knew about the attractive property of the resin amber. They knew that by rubbing amber with cloth, it could be made to attract small feathers. The Greek name for amber was 'elektron'.
Static electricity is defined as the deposition of electrical charges or electrons on the surface of a material. They are generally caused when a material is rubbed against the surface of another material. Though electrical charges are present they do not constitute to form an alternating current or a direct current. Hence, these are referred to as "static" which explicitly means "electricity at rest".
Causes of Static Electricity
When two materials come into physical contact against each other, the electrons are shifted from the surface of one material to the other’s surface. The material which supplies the electrons attains extra positive charges called as protons and the other material which gains the electrons attain extra negative charges called as neutrons.
The process of static electricity doesn’t purely mean the conduction of electricity. It is found that m
ost of the materials that have the ability to exhibit static electricity are non conductors of electricity.
A common fact to note is the circumstance when static electricity is exhibited. When the humidity of air is higher than usual, there is high probability of the presence of water particles on the elements. This hinders the deposition of electrical charges on its surface since the water molecules are bound to repel the charges. Therefore it is implied that the process of static electricity is better exhibited when the air is less humid.
Practical Uses:
The common uses of static electricity are in Xerography or electro-photography, Air filters, Automotive paints, Spray paintings.
Most of the modern photocopy machines use static electric charges to make photo copies of documents. Recently invented laser and LED printers also use static electricity.
Since static electricity is an inter-combination of electric charges (protons and neutrons) on two materials that are separated from each other, there is a high probability of small electrical and electronic components getting damaged due to its impact. Hence, manufacturers of such devices have started using a number of antistatic devices to avoid the effect.
Proof of Static Electricity
It is well known that opposite charges attract each other whereas like charges repel each other. Therefore the existence of static electricity can be proved if an object with static electrons on its surface attracts another object which has electrons of the opposite charge.
Consider a metal rod which is initially neutral with equal amount of positive and negative charges on it. When the rod is rubbed against a rough surface for a while, it is bound to achieve positive charges on its surface. Now, it is taken near a small metal bead which is neutral. The rod is found to attract the bead thus proving the process of static electricity. The same rod, when taken near another metal bead which has been rubbed against a metal surface and made to conduct negative charges, is found to push away the bead since like charges repel.
Effects:
By experiments, it has been found that an object which has electrons deposited on it attracts an oppositely charged object with a greater attraction than an object with neutral charges. This is because the strong molecular bonding of the electrons with the surface of the material keeps the electrons intact. But when an oppositely charged object is brought near it, the electrons are attracted with a greater force that they break the strong molecular bonding and jump across to the other object. When more and more electrons fly across the objects, the air surrounded by then gets heated up and this induces the other electrons to switch over to the receptor object. This eventually leads to a situation when both the elements acquire neutral charges.
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