Basic Physical Concepts Electrical Engineering|Atoms,Protons, Neutrons, and Atomic Numbers
It
is important to understand some simple, general physics principles in order to
have a full grasp of electricity and electronics.
Atoms
All matter is made up of countless tiny particles whizzing around. These particles are extremely dense; matter is mostly empty space.
Matter seems continuous because the particles are so small,and they move incredibly fast.
Each chemical element has its own unique type of particle, known as its atom.
Atoms of different elements are always different. The slightest change in an atom can make a tremendous difference
in its behavior.
Eg:- Take the Example of Oxygen and Nitrogen. Both are having different behavior both are gases at room temperature and pressure; both are colorless, both are odorless, and both are just about of equal weight. These substances are so different because oxygen has eight protons, while nitrogen has only seven.
Protons, Neutrons, and Atomic Numbers
The part of an atom that gives an element its identity is the nucleus.
It is made up of two kinds of particles, the proton and the neutron. These are extremely dense. Protons and neutrons have just about the same mass, but the proton has an electric charge while the neutron does not.
The simplest element, hydrogen, has a nucleus made up of only one proton; there are usually no neutrons.This is the most common element in the universe.
The second most abundant element is helium. Usually, this atom has a nucleus with two protons and two neutrons.
Hydrogen is changed into helium inside the sun, and in the process, energy is given off. This makes the sun shine. The process, called fusion, is also responsible for the terrific explosive force of a hydrogen bomb.
Every proton in the universe is just like every other.
Neutrons are all alike, too.
The number of protons in an element’s nucleus, the atomic number, gives that element its identity.
The element with three protons is lithium, a light metal that reacts easily with gases such as oxygen or chlorine.
The element with four protons is beryllium, also a metal.
In general, as the number of protons in an element’s nucleus increases, the number of neutrons also increases.
Elements with high atomic numbers, like lead, are therefore much denser than elements with low atomic numbers, like carbon.
Isotopes and Atomic Weights
For a given element, such as oxygen, the number of neutrons can vary. But no matter what the number of neutrons, the element keeps its identity, based on the atomic number.
Differing numbers of neutrons result in various isotopes for a given element.
Each element has one particular isotope that is most often found in nature.
But all elements have numerous isotopes.
Changing the number of neutrons in an element’s nucleus results in a difference in the weight, and also a difference in the density, of the element.
Thus, hydrogen containing a neutron or two in the nucleus, along with the proton, is called heavy hydrogen.
The atomic weight of an element is approximately equal to the sum of the number of protons and the number of neutrons in the nucleus.
Common carbon has an atomic weight of about 12, and is called carbon 12 or C12.
But sometimes it has an atomic weight of about 14, and is known as carbon 14 or C14.
Electrons
Surrounding the nucleus of an atom are particles having opposite electric charge from the protons.These are the electrons.
Physicists arbitrarily call the electrons’ charge negative, and the protons’charge positive.
An electron has exactly the same charge quantity as a proton, but with opposite polarity.
The charge on a single electron or proton is the smallest possible electric charge.
All charges,no matter how great, are multiples of this unit charge.
One of the earliest ideas about the atom pictured the electrons embedded in the nucleus, like raisins in a cake.
Later, the electrons were seen as orbiting the nucleus, making the atom like a miniature solar system with the electrons as the planets
Today, the electrons are seen as so fast-moving, with patterns so complex, that it is not even possible to pinpoint them at any given instant of time.
All that can be done is to say that an electron will just as likely be inside a certain sphere as outside. These spheres are known as electron shells. Their centers correspond to the position of the atomic nucleus.
The farther away from the nucleus the shell, the more energy the electron has Electrons can move rather easily from one atom to another in some materials.
In other substances, it is difficult to get electrons to move. But in any case, it is far easier to move electrons than it is to move protons.
Electricity almost always results, in some way, from the motion of electrons in a material.
Electrons are much lighter than protons or neutrons.
In fact, compared to the nucleus of an atom, the electrons weigh practically nothing.
Generally, the number of electrons in an atom is the same as the number of protons.
The negative charges therefore exactly cancel out the positive ones, and the atom is electrically neutral.
But under some conditions, there can be an excess or shortage of electrons.
High levels of radiant energy, extreme heat, or the presence of an electric field (discussed later) can “knock” or “throw” electrons loose from atoms, upsetting the balance.
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