Dafinations

Insulator:-
Insulator are those materials that have very few free electrons and require a large applied voltage to establlish a measureable current level.
Semiconductor:-
Semiconductor are a specitic group of elements that exhibit characteristics that lie between those of insulators and conductors.semiconductor materials have four electrons in the outermost orbit.


Conductor:-
Conductors are those materials permit a generous flow of electrons with very little external force (voltage) applied.Good conductors have only one electron in valance ring.Resistance:-
The property of a substance which opposes the flow of electricity throught it is called resistance or resistance is the ability of a circuit to oppose current.
Conductance:-
Reciprocal of resistance is called conductance.
G=1/R OR R=1/G

Ohm,s law:-
In any electric circuit the current is directly proportional to the applied voltage and inversely proportional to the total circuit resistance.
I=V/R

V=IR

R=V/I

Temperature Co-efficient:-
Temperature co-efficient of resistance is the amount by which resistance changes when temperature changes when temperature change by one degree centigrat.

Resistors:-
A resistor is a component designed to have a known value of resistance or those components which are specially designed to have a certain amount of resistance are called resistors.

Work:-
If a force move a body throught a distance in the direction of application then work is done.
W=FS

power:-
Is the rate of doing work or power is the rate at which energy is used or power is the rate of converting energy.
P=W/T

Energy:-
Energy is capaacity for doing work or the ability to do work is called energy.

Magnetic field:-
Any space in which a magnetic effect can be detected constitutes a magnetic field.

Magnetic flux:-
The total number of lines threading throught the filed is called the magnetic flux.

Classification of magnetic materials:-
1:-Dia magnetic
2:-Paramagnetic
3:-Ferromagnetic

Dia magnetic materials:-
Materials made up of atoms having zero magnetic moment prove to be weakly repelled by a magnetic.They are called diamagnetic or non magnetic materials.

Paramagnetic materials:-
Tha materials have a permeabillity just slightly greater than that of space and are very slightly magnetised are called paramagnetic materials,e.g platinum alumlnum and oxygen etc.

Feromagnetic materials:-
The materials which can be magnetised very strongly are called ferromagnetic materials e.g iron cobalt or nickle.

Cycle:-
One complete set of positive and negative values of alternating quantity is known as caycle.

Period:-
The time taken by an alternating quantity to complete one cycle is called its time period.
T=1/F

Frequency:-
Frequency is the number of cycles passed thrpught per second.It is denoted by f and has the unit cycle per second.

Amplitude:-
The maximum value positive or negative of an alternating quantity is known as its amplitude.

Ac motor vs Dc motor

Electric motors can be divided into two types.

1.Alternating current (Ac) electric motor.

2.Direct current (Dc) electric motor.

A dc electric motor will not run when supplied with ac current,nor will an ac motor run with dc current.Ac electric motor are further subdivied into single phase and three phase motors.Single phase ac electrical supply is what is typically supplied in a home.Three phase electrical power is commonly only available in a factory setting.

Dc electric motors are also split into types.There include brush motors brushless motors and stepper motors of these types brush electric motors are by for the most common.They are easy to build and very cost effective.Their major draw back is that they use corbon brushes to transfer electrical current to the rotating part,and these brushes wear over time and eventually result in the failure of the electric motpr.The dc brushless motor eliminates the brushes but is more costly and requires much more complicated drive electronics to operate.

Transformer

A transformer is a device that transfers electric energy from one cercuit to another throughinductive couples conductors — the transformer's coils. Except for air-core transformers, the conductors are commonly wound around a single iron-rich core, or around separate but magnetically-coupled cores. A varying current in the first or "primary" winding creates a varying magnetic feild in the core (or cores) of the transformer. This varying magnetic field induces a varying electrimotive force(E
MF) or "vlotage" in the "secondary" winding. This effect is called mutual induction.

If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will flow from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (V_S) is in proportion to the primary voltage (V_P), and is given by the ratio of the number of turns in the secondary to the number of turns in the primary as follows:

By appropriate selection of the ratio of turns, a transformer thus allows an alternating current(AC) voltage to be "stepped up" by making N_S greater than N_P, or "stepped down" by making N_S less than N_P.

Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of national power grids. All operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for house hold voltage. Transformers are essential for high voltage power transmition, which makes long distance transmission economically practical.

Electricity

Electricity (from the latin ēlectricus, "amber-like") is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lighting and static electricity, but in addition, less familiar concepts, such as the electromagnetic field and electromagnetic indution.

In general usage, the word 'electricity' is adequate to refer to a number of physical effects. However, in scientific usage, the term is vague, and these related, but distinct, concepts are better identified by more precise terms.

I=Q/T