Electrostatic Shielding

What is electrostatic shielding?

Electrostatic shielding, in its simplest terms, is any activity that blocks the electric field created by a particular source. The most popular electrostatic shielding apparatus is the Faraday Cage.

What happens when a field is applied to a Faraday's cage?

(Photo credit: Boundless.com)

As the field is applied, the negative charge from the cage migrates toward the positive end of the field, canceling the effects of the field at both ends of the cage.

Thus when a field is applied to the cage, the charges in it rearrange so as to counteract the field and shields the objects inside.

Faraday cages are popularly used for automobiles. When a high voltage or a large electric field as in the case of lightning is struck on the vehicle, as shown above, the charges rearrange themselves so that there is no internal effect from the field. The total magnitude of the field inside the cage is zero.

(Photo credit: tesladownunder.com)

Furthermore, the action of a Faraday Cage depends upon whether it is grounded. If a Faraday cage is grounded excess charges on the interior of the cage would move towards the ground making the external cage void of net charges. Thus the external cage is neutral in charge.

(Photo credit: thebigger.com)

However, if the external cage is not grounded, the charges will redistribute so that there is a charge difference between the external carriage and the internal carriage.

(Photo credit: thebigger.com)

Note: It is not necessary that hollow conductors must be used. An earthed conductor can also protect the objects inside against an electric field.

Action of a transistor

In this note I will present details only about the npn transistor. For those who are interested only on the pnp transistor, you can switch the action of the npn transistor and the behavior of current to adjust with the characteristics of the pnp transistor. (Photo credit: mahasona10000.blogspot.com ) As in the case of a p-n junction,the two n parts of the npn transistor contain an excess of free electrons. In contrast, the p part contains excess holes. As in the case of the p-n junction, in the npn transistor depletion regions develop and junction barriers occur. (Photo credit: daenotes.com) For the correct functioning of the transistor, the first p-n junction is forward biased and the second p-n junction is reverse biased. This results for the first p-n junction to be of low resistance and the second p-n junction to be of high resistance. (Photo credit: www.nzart.org.nz ) The letters of these elements

Gold leaf electroscope

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What is electromagnetic induction? When an alternative current is allowed to flow through a certain circuit and that circuit is kept near a neutral circuit, the former circuit induces charge distributions in the latter circuit resulting in an induced current in the latter circuit. This phenomenon is called the electromagnetic induction. Thus a potential difference arises across the circuit when exposed to a varying magnetic field. Faraday's law- Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be "induced" in the coil. (Photo credit: gic-edu.com) Thus, fluctuating magnetic fields cause currents to flow in conductors placed within them. This is called induction because there is no physical connection between the conductor and the magnet. The current is said to be induced in the conductor by the magnetic field. In order to produce the maximum force needed for induction, usually the cond

Flame test- By Aditya Abeysinghe

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