Basics for Electrical Engineers.

      Without knowing the fundamentals, Laws, principle behind the concepts study become hard, makes more difficult the learning process. Some of the basic rules and concepts are important to understand the electrical machines.

     Most of the electrical machine's principles running around the electromagnetic induction concepts. Initially the DC source invented using battery using coins, chemicals. till the invention Alternating current (AC). In 1931 Michael faraday found that the flux changing causing the induction of e.m.f i.e. electro motive force.

But now-a- days maximum we are using the AC, with the desired voltage with the help of transformer. it is good to know the laws and principles behind this which are helping silently.

Faraday's Experiment: 

• Consider a coil C of several turns connected to a central zero galvanometer.
• If a permanent magnet is moved towards the coil it will be observed that the galvanometer shows deflection in one direction. 
• If the magnet is moved away from coil, the galvanometer again shows deflection but in opposite direction. 
• Deflection of galvanometer indicates there is a current flow through the coil. 
• For the current to flow, there must be an EMF in the coil. 
• Hence it is concluded that when magnetic flux linking a conductor or coil changes an EMF is induced in it.

Image Source: https://sites.suffolk.edu/ekprime/2011/04/05/faradays-law-with-flashlights/

Faraday's laws of electromagnetic induction: 

First law: Whenever the magnetic flux linking a conductor or coil changes, an EMF is induced in it. 

Second law: The magnitude of the EMF induced in a conductor or coil is directly proportional to the rate of change of flux linkage. Here the minus sign of the RHS represents the Lenz's law

induced emf,  e α dɸ/dt 

e = - N dɸ/dt

Direction of induced EMF and current: The direction of induced EMF and current can be determined by one of the following two methods 1.Lenz's law 2.Fleming's right hand rule. 

Lenz's law: The induced current will flow in such a direction so as to oppose the cause that produces it. In this case, the cause for the induced current is the increasing magnetic flux linking the coil. Therefore the induced current will set up magnetic flux that opposes the increase in flux through the coil. 

Fleming's right-hand rule: This law is used to find the direction of the induced EMF of DC generator. 

• Hold the fore finger, middle finger and thumb of the right hand so that they are at right angles to one another. 
• If the fore finger points in the direction of magnetic field, thumb in the direction of motion of conductor then the middle finger will point the direction of induced current. 

for DC motor Fleming's left-hand rule will be used, and other few basic rules and concepts are as follows.

Right Hand Thumb Rule:

Hold the conductor in the right hand with the thumb pointing in the direction of current as shown in the figure. Then the fingers will point the direction of the magnetic field around the conductor

Cross and Dot notation: 

•  Cross and Dot notation can be used to indicate the direction of current flow. 
• Current flowing away from observer is indicated by cross. 
• The cross is based on the tail of an arrow moving away from the observer. 
• Current flowing towards an observer and is indicated by a dot. 
• The dot is based on the point of an arrow moving towards the observer.