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• A diode is an electrical device which allows current to flow easily in the circuit. 
• The most common form of diode is semiconductor diode 
• Symbol of a diode  

Introduction to Semiconductor Diodes:-

These are the following types of diodes: 

• It is an electric device that transfers energy between two circuits using Electromagnetic Induction. 
• Operation of transformer 

1. The operation of a transformer can be explained with the help of these two laws: Electric current produces magnetic field across the conductor and a change in magnetic field induces voltage at the ends of the conductor. 

• Features of Transformer
  

1. There is no copper loss in the windings 
2. There is no inductive loss 
3. Flux is present only within the magnetic core 

• Construction of Transformer

Based on the application, a transformer consists of a core made up of ferromagnetic or ceramic material and a coil made up of some insulating magnetic material or copper wires. Transformer oil is used for cooling transformer

• Losses in a Transformer 

• These are the losses in a transformer: 

1. Winding loss 
2. Hysteresis loss 
3. Eddy current loss 
4. Hum Stray loss 

• Winding losses: Current flowing through windings causes heating and losses due to heating. 
• Hysteresis losses: Each time the magnetic field is reversed, some energy is lost. It is hysteresis loss. 
• Eddy current losses: Eddy currents are present in the ferromagnetic core and cause resistive heating in the core. 
• Hum: Magnetic flux causes the core to physically expand slightly and it results in a humming noise. 
• Stray losses: Inductive leakage and radiation losses are all stray losses in an inductor.

                   Types of Transformers

• Based on the purpose of transformers, they are classified into Power transformers, Instrument transformers, RF transformers, Audio Transformers.

1. Power Transformer: Used for high voltage transmission purposes. 
2. Instrument Transformer: They are used to operate instruments at high voltage, high current cicuits and safely isolate the control circuit. 
3. RF Transformer: Transformers used in Radio Frequency applications. 
4. Audio Transformer: They block radio frequency signals, split and combine audio signals.

• The following are the types of inductors: 

1. Air core inductor, 
2. Ferromagnetic core inductor, 
3. variable inductor

• Air core inductor: It is an inductor which has its coil wound on non­magnetic material like plastic or ceramic and there is only air present in between the windings. 
• Ferromagnetic inductor: It is an inductor which has its coil wound on a magnetic core made up of ferromagnetic or ferromagnetic material.

 Laminated core: It is a type of ferromagnetic inductor whose core is made up of thin steel sheets or laminations. 

Ferrite core: It is a type of ferromagnetic inductor whose core is made up of ferrite. 

Torroidal core: It is a type of ferromagnetic inductor where the coil is wound on a straight rod shaped core. 

Choke: It consist of a coil of insulating material wound on a magnetic material.

• Variable inductor: It is made up of ferrite magnetic core which can be slid or screwed to change inductance. 

Features of inductor:-

• Inductors are used in

1. Signal Processing 
2. Filtering out some frequencies 
3. Removing hums from DC output

• All materials have inherent magnetic characters formed due to the movement of electrons. 
• Transition metals, lanthanides and their compounds are used as magnetic materials. 
• The properties of magnetic materials are: 

1. Paramagnetism, 
2. Ferromagnetism, 
3. Antiferromagnetism, 
4. Ferrimagnetism. 

                  Introduction to inductor

• *An inductor is a two terminal electric component which resists changes in electric current. 
• *It is a conductor wire wound into coil. 
• *Construction of Inductor 

1. >Inductors are made up of insulating wire like copper wire wound on a plastic or ferromagnetic material. 
2. >The inductor symbol is shown. 
   

• Working :-

1. When current flows through the coil, a magnetic field is set. 
2. This field restricts the flow of current. 
3. Once the field is created then current passed normally through it thus resisting any change in the flow of current. 

• Characteristics:-

1. The resistance of the wire used in winding the coil is assumed negligible. 
2. The amount of induced voltage in a coil is directly proportional to the rate of change of magnetic field of coil. 
3. The induced voltage of the coil is proportional to the number of turns. 

• Based on the type of materials used in the capacitor plates, the following types are the most common types of capacitors: Ceramic Capacitors, Film Power Capacitors, Super Capacitors and Variable Capacitors. 

1. Ceramic Capacitors: Ceramic capacitors are made up of ceramic and metal where metal acts as the electrode and ceramic is the dielectric. This type of capacitor is used in applications of high frequency and high current pulse loads. 
2. Film Power Capacitors: In film power capacitors, the dielectric films are drawn to a thin layer surrounded by metallic electrodes on a cylindrical wiring. Polypropylene is used as the dielectric. 
3. Super Capacitors: Super capacitors are electrochemical capacitors with no specific dielectric in it. The storage of charge is obtained by either separation of charge or redox reactions. 
4. Variable Capacitors: All the above mentioned capacitors are fixed capacitors which cannot vary their capacitance. A variable capacitor can vary its capacitance by mechanical motion. 

The 2 methods used to vary capacitance are tuning and trimming

Applications of capacitor:-

• Capacitors are used in designing filters. They are used to reduce the impact of electric noise in digital circuits. Also to separate the AC components of a signal from DC components. Large capacitors are used to store energy. 
• Safety with capacitors: Capacitors retain charge for a long time even after the power is removed. So before touching the circuit, ensure that the capacitor is fully discharged.