Electricity – Some Important Definition
Some Important Definitions
A form of energy resulting from the existence of charged particles such as electrons or protons.
Electric charge is a basic property of electrons, protons and other subatomic particles.
Those substances through which electricity can flow are called conductors.
Those substances through which electricity cannot flow are called insulators.
The presence of “free electrons” in a substance makes it a conductor (of electricity).
In static electricity, the electric charges remain at rest (or stationary), they do not move.
In current electricity, the electric charges are in motion (and produce an electric current)
The electric potential (or potential) at a point in an electric field is defined as the work done in moving a unit positive charge from infinity to that point.
The potential difference between two points in an electric circuit is defined as the amount of work done in moving a unit charge from one point to the other point.
The electric current is a flow of electric charges (called electrons) in a conductor such as a metal wire.
A continuous conducting path consisting of wires and other resistances (like electric bulb, etc.) and a switch, between the two terminals of a cell or a battery along which an electric current flows, is called a circuit.
At constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its ends.
The ratio of the potential difference applied between the ends of a conductor and the current flowing through it is a constant quantity called resistance.
Those substances which have very low electrical resistance are called good conductors.
Those substances which have comparatively high electrical resistance, are called resistors
A superconductor is any material that can conduct electricity with no resistance.
Resistivity of the material is defined as the resistance offered to current flow by a conductor of unit length having unit area of cross-section.
Conductivity defines a material’s ability to conduct electricity. Electric current can flow easily through a material with high conductivity.
A material that is neither a good conductor of electricity nor a good insulator, but has properties of electrical conductivity somewhere between the two.
An alloy is a substance made by melting two or more elements together, at least one of them metal.
an electric current that reverses its direction many times a second at regular intervals, typically used in power supplies.
Direct current is the unidirectional flow of an electric charge.
Electric power is the electrical work done per unit time.
Heating Effect Of Current
When an electric current is passed through a high resistance wire, like nichrome wire, the resistance wire becomes very hot and produces heat. This is called the heating effect of current.
Some Important Definitions of Units
One coulomb is that quantity of electric charge which exerts a force of 9 x 109 newtons on an equal charge placed at a distance of 1 metre from it.
The potential difference between two points is said to be 1 volt if 1 joule of work is done in moving I coulomb of electric charge from one point to the other.
When I coulomb of charge flows through any cross-section of a conductor in 1 second, the electric current flowing through it is said to be 1 ampere.
1 ohm is the resistance of a conductor such that when a potential difference of 1 volt is applied to its ends, a current of 1 ampere flows through it.
The resistivity of a substance is numerically equal to the resistance of a rod of that substance which is 1 metre long and 1 square metre in cross-section.
The power of 1 watt is a rate of working of 1 joule per second.
One kilowatt-hour is the amount of electrical energy consumed when an electrical appliance having a power rating of 1 kilowatt is used for I hour.