DC BASICS AND NETWORKS AND ELECTROMAGNETIC THEORY

ELECTRICAL ENGINEERING BASIC DEFINITIONS

• ELECTRIC CURRENT:- The controlled movement of electrons through a substance is called electric current.
• ELECTRO MOTIVE FORCE AND POTENTIAL DIFFERENCE:- It is the force that causes an electric current to flow in an electric circuit while the potential difference between two points in an electric circuit is that difference in their electrical state which tends to cause flow of electric current between them.
• RESISTANCE:- Resistance may be defined as that property of a substance which opposes the flow of an electric current through it.
• OHMS LAW:-The current flowing through a conductor is directly proportional to the potential difference across the ends or the conductor and inversely proportional to the conductor resistance .
• CONDUCTANCE:- The reciprocal of resistance is called the conductance. It is the inducement offered by the conductor to the flow of current.
• CONDUCTORS:- The meterials which have least resistance and allow the flow of electric current easily.
• INSULATORS:- The meterials which have high resistance and does not allow the flow of electric current easily.
• SEMICONDUCTORS:- The meterials lying between conductors and insulators.
• JOULE'S LAW:-The amount of heat produced in an electric circuit is proportional to the square of the current and proportional to the resistance of the circuit and also proportional to the time duration for which the current flows through the circuit.
• KIRCHHOFF'S CURRENT LAW:- The algebraic sum of all currents meeting at a point is zero or the sum of incoming currents towards any point is equal to the sum of outgoing currents away from that point.
• KIRCHHOFF'S VOLTAGE LAW:- The algebraic sum of emfs acting in that circuit is equal to the algebraic sum of the products of the currents and resistances of each part of the circuit.
• FIELD STRENGTH OR FIELD INTENSITY OR ELECTRIC INTENSITY:- The force experienced on an unit positive charge placed at any point in an electric field is known as electric field strength or field intensity or electric intensity.
• ELECTRIC FLUX DENSITY:- Electric flux density is defined as the no of tubes of force per unit area emanated normally from the surface.
• GAUSS'S THEOREM:- The total flux traversing a surface completely surrounding the charge of Q coulombs is Q.This is known as gauss's theorem.
• COULOMB'S THEOREM:- The electric intensity at a surface of conducting body ,having a charge density of a coulombs per unit of surface area is the absolute permitivity of the medium surrounding the conductor.
• POTENTIAL:- In general potential at any point in an electric field is defined as the work done in moving a unit positive charge from infinity to that point.
• POTENTIAL DIFFERENCE:- The potential difference between two points in an electric field is defined as the work done in moving a unit positive charge from one point of lower potential to the point of higher potential.
• POTENTIAL GRADIENT:- Potential gradient is the rate of change of potential with distance measured in the direction of electric force. Electric intensity at any point is equal to the negative potential gradient at that point.
• CAPACITORS:-Two metal plates seperated by an insulator. The capacity of storing electricity in excess of electrons on one plate and a deficiency on the other.
• CAPACITANCE:-The property of a capacitor to store electric charge and the charge required to raise its potential through unity.
• MAGNETIC FIELD:-The space around the poles of a magnet is called magnetic field and is represented magnetic lines of force.
• MAGNETIC FLUX:-Magnetic flux is the total number of lines of force , comprising the magnetic field .
• MAGNETIC FLUX DENSITY:- Magnetic flux density is the flux passing per unit area through any meterial through a plane at right angles to the direction of flux.
• FARADAY'S FIRST LAW:- This law states that when the flux linking with the coil or circuit changes an emf is induced in it or whenever the magnetic flux is cut by the conductor an emf is induced in the conductor.
• FARADAY'S SECOND LAW:- This law states that the magnitude of emf induced is directly proportional to the rate of change of flux linkage or to the product of number of turns and rate of change of flux linking the coil.
• LENZ'S LAW :-This law states that the direction of induced emf is such that the current produced by it sets up a magnetic field opposing the motion or change producing it.