electrical theory and electrical fundementals for all electrical related people . students , engineers, electrician #electricaltheorems,electrical,
Georg Ohm
The statement of Ohm’s law is simple and it says that, whenever a potential difference or voltage is applied across a resistor of a closed circuit, current starts flowing through it. This current is directly proportional to the voltage applied if temperature and all other factors remain constant. Thus we can mathematically express it asV is directly proprtional to I
Now putting the constant of proportionality we get,
V=IR
This particular equation essentially presents, the statement of this law where I is the current through the resistor in unit of Ampere, when the potential difference V is applied across the resistor in unit of volt, and ohm(&Ohm;) is the unit of resistance of the resistor R.
It’s important to note, that the resistance R, is the property of the conductor and theoretically it has no dependence on the voltage applied, or on the flow of current. The value of R changes only if the conditions (like temperature, diameter, length etc.) of the material are changed by any means.
electrical theory and electrical fundementals for all electrical related people . students , engineers, electrician #electricaltheorems,electrical,
In 1831, Michael Faraday, an English physicist gave one of most basic law of electromagnetism called Faraday's law of electromagnetic induction . This law explains the working principle of most of electrical motors , generators, electrical transformer s and inductors. This law shows the relationship between electric circuit and magnetic field. Faraday performs an experiment with a magnet and coil. During this experiment he found how emf is induced in the coil when flux linked with it changes. He has also done experiments in electrochemistry and electrolysis .
experiment Faraday takes a magnet and a coil and connects a galvanometer across the coil. At starting the magnet is at rest so there is no deflection in the galvanometer i.e needle of galvanometer is at centre or zero position. When the magnet is moved toward the coil, the needle of galvanometer deflects in one direction. When the magnet is held stationary at that position, the needle of galvanometer returns back to zero position. Now when the magnet is moved away from the coil , there is some deflection in the needle but in opposite direction and again when the magnet become stationary at that point with respect to coil , the needle of galvanometer return back to zero position. Similarly if magnet is held stationary and the coil is moved away and towards the magnet, the galvanometer shows deflection in similar manner. It is also seen that the faster the change in the magnetic field, the greater will be the induced emf or voltage in the coil.
electrical theory and electrical fundementals for all electrical related people . students , engineers, electrician #electricaltheorems,electrical,
Induction Motor
One of the most common electrical motorused in most applications which is known as induction motor. This motor is also called as asynchronous motor because it runs at a speed less than synchronous speed. In this, we need to define what is synchronous speed. Synchronous speed is the speed of rotation of the magnetic field in a rotary machine and it depends upon the frequency and number poles of the machine. An induction motor always runs at a speed less than synchronous speed because the rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor to rotate, but due to the lagging of flux current in the rotor with flux current in the stator, the rotor will never reach to its rotating magnetic field speed i.e. the synchronous speed. There are basically two types of induction motor that depend upon the input supply - single phase induction motor and three phase induction motor. Single phase induction motor is not a self starting motor which we will discuss later and three phase induction motor is a self-starting motor
Working Principle of Induction Motor
It is very simple, from the name itself we can understand that there is induction process occurred. Actually when we are giving the supply to the stator winding, flux will generate in the coil due to flow of current in the coil. Now the rotor winding is arranged in such a way that it becomes short circuited in the rotor itself. The flux from the stator will cut the coil in the rotor and since the rotor coils are short circuited, according to Faraday's law of electromagnetic induction, current will start flowing in the coil of the rotor. When the current will flow, another flux will get generated in the rotor. Now there will be two flux, one is stator flux and another is rotor flux and the rotor flux will be lagging to the stator flux. Due to this, the rotor will feel a torque which will make the rotor to rotate in the direction of rotating magnetic flux. So the speed of the rotor will be depending upon the ac supply and the speed can be controlled by varying the input supply.
