Electric Charge
Electric charge is defined as “The ability of electrical
interaction of a particle around it is determined by its electric charge”. For Example:
like charges repel each other and unlike charges attract each other. The object
of the equal amounts of the two kind of charge is said to be electrically neutral.
The object with inequality amount of the two kinds of charge is said to be
electrically charged.
All materials including solids, liquids and gases consist of
two basic particles of electric charge named as electrons and protons. The
electron is negatively charged and the proton is positively charged.
Basically it is the collection of electrons and protons that
limits the electrical properties of all the substances. The distribution of
electrons occurs when one material is rubbed against the other .The material
that loses the electrons is said to be positively charged while the material
that gains the electrons is negatively charged.
Example
Take a rod of any material which is positively charged and
then rub it with the silk for a few times. The silk will be negatively charged.
Unit of Charge
The system international unit of charge is one coulomb which
is equal to 6.25 x 1018 electrons
or protons. The sub-multiple units of charge are μC, nC and pC etc.
Electrostatics
Electrostatics is defined as “The study of electric charges
at rest under the action of electric forces is said to be electrostatics”.
Types of Charges
The charge consists of its two types which are as follows:
Positive Charge
The material that loses the electrons is said to be
positively charged.
Negative Charge
The material that gains the electrons is negatively charged.
Polarity of Charges
Same polarity of charges repels each other while charges of
opposite polarity attract each other. The positive and the negative charges are
random and allocated by the Franklin.
Charge on Electrons
The mass of an electron is 9.1 x 10-31 kg and the
magnitude of charge of one electron is 1.6 x 10-19C. It is measured
by Millikan.
Charge on Protons
The magnitude of charge of one proton 1.6 x 10-19C
and the mass of proton is 1.67 x 10-27kg.
Charge on Neutrons
The neutron has no charge and its mass is equal to the mass
of proton.
Poles of Charge
The poles according to the charge are as follows:
- A material which is isolated and consists of a single charge is said to be electric mono pole.
- The materials of positive and negative charges that have constant separation with each other are said to be electric dipole.
- Whereas the two oppositely directed poles which are close to each other are said to be quadrupole.
Conductors
These are the materials in which charges can flow easily and
are said to be conductors.Some properties of conductors are as follows:
- The copper and aluminum are the good conductors and are used commonly in different fields of electrical as well as electronic circuits.
- The electrons are mobile and the positive ionic cores are immobile within conductor.
- The valance band and the conduction band overlaps in conductors so the electrons can move very easily.
- The resistivity of a conductor is 10-6Ω-m while the resistivity of copper(Cu) is 1.77 x 10-6 Ω-m.
Semi-Conductors
Semi-conductors are partial conductors. These are neither a
conductor nor an insulator. These materials are between insulators and conductors.
A semi-conductor material consists of 4 electrons in their outermost shell.
When temperature increases these materials become insulator and when these are
connected to electric field, these materials become conductors. The examples of
semiconductors are silicon and germanium. A typical semiconductor has 1012
conduction electrons/cm3.
Insulators
These are the materials in which charges cannot flow are
said to be insulators. The electrons are tightly bounded with each other in
these materials. The most common examples of insulator are glass and plastic. An
insulator consists of only one conduction electron/cm3.
The resistivity of insulators is 1011---1016
Ω-m. The resistivity of glass is 2 x 1011 Ω-m. The energy gap
between the conduction gap and the valance band in insulator is very high and
electrons present in these materials cannot jump from valance band to
conduction band.
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