Self-inductance of a solenoid 

Self-inductance is a process of induction of emf or voltage in a winding. A coil induces emf when the magnetic flux of the coil or current in the coil changes. When the currents start to flow in the coil at any instant, magnetic flux is directly proportional to the current passing through the coil. A magnetic field is created by changing the current in the winding and this winding itself induces a voltage. the solenoid is a long coil of metallic wire. It is an electromagnet  When an electric current is passed through the solenoid, a magnetic field is produced around the turns of the coil. 

The self-inductance of a solenoid depends upon the number of turns per unit length of the solenoid, the permeability of the material, and the cross-sectional area of turns. 

 Self-inductance formula, 

            L=N flux/current.   L is the self-inductance, N is the number of turns.

Self-inductance of the solenoid can be defined as that magnetic flux linked to the solenoid when current is passed so, the amount of current is the same in each turn or loop.  Emf in the coil as, e = -LdI/dt 

The direction of induced emf is such that it opposes the cause by which it is produced, that is to oppose the change in the current. 

As the inductance of the solenoid depends upon the number of turns and cross-sectional area of the solenoid. For increasing the self-inductance of the solenoid, we can either increase the number of turns or by increasing the diameter of the turns of the solenoid. 

Self induction in a solenoid

Mutual induction principle

 Mutual induction

Mutual induction between two coils

When current flows through one coil or winding and, induced emf or voltage is produced in another coil. Mutual induction is characteristic of pair of coils. If two coils of a conducting wire are brought together so that the magnetic field from one coil links with the other, a voltage will be generated in the second coil. Mutual induction is the process of producing E.M.F in a coil when the current in the proximate coil change. Mutual induction is the basic operating principle of a transformer and other electrical machines or devices. When power is supplied to a coil, current flows in that coil or winding and produces a magnetic field, and induces a voltage in the neighboring winding. When emf induce in the adjacent coil. When two or more coils are linked magnetically with the same magnetic field then they possess mutual induction. 

Mutual induction

Let's consider we have two coils that are placed together when current is passed through the primary coil, magnetic flux is produced. If current changes in the coil, flux also changes, and flux links with the second coil. This changing flux produces induced emf in the secondary coil. This whole phenomenon of induced emf in a coil by a change in current and flux in another coil is the principle of mutual induction. A transformer also works on the principle of mutual induction. Which consist of two coils primary and secondary coils and magnetically connected. When power is supplied to the primary coil current flows through the coil and produces a magnetic flux that links with the secondary coil and induced emf produced. There are applications of mutual induction such as generators, induction motors, transformers, digital signal processing, and other electrical machines and devices.

Emf induces in the second coil when a change in flux in the first coil link to another coil

How does an electric generator work?

An electric generator is a device that is designed for the generation of electrical energy. An electrical generator is a machine that converts mechanical energy, into electrical energy. The generators input mechanical power and output electrical power. The generator has the inverse function of a motor. Just as an electric motor changes electrical to mechanical power, so an electric generator changes mechanical power to electrical power. Almost the working process and construction are the same in both motor and generator. There is little difference between these machines. The generator works on the principle of electromagnetic induction. Magnets in a generator create a magnetic field and then generates electricity. In the generators, the mechanical power produces motion and rotation as torque and generates electrical power. The electric generator gets mechanical energy inputs and provides us electrical energy output. Electric motors and generators have many similarities. A motor can be converted into a generator mechanically. Alternating current flows through the coil of the generator and changes its direction continuously. Mainly an electric generator is consists of a current-carrying conductor or coil, magnetic field, and ac supply. Fleming's right-hand rule can be used for knowing the direction of motion of the coil, and current in the coil. 

Electrical generators

There are also other components of the generator like carbon brushes, and commutators These parts of the generator play a sufficient role in the working of generators efficiently. A conductor coil wounded on the metal core is rotated between the poles of a magnet and the magnetic field interacts with the electrons of the conductor to induce electric current and by this way, electric energy is produced.  Generators are used in industries, power stations, grid stations, and more. sources of mechanical power are wind turbines, water turbines, and steam turbines, etc. An electric generator is consists of a rotating part and a stationary part. A rotor is a rotating part whereas a stator is a stationary part in a machine.

 In an electric generator rotor's rotation is due to the interaction between the windings and magnetic field which produce torque around the rotor's axis. There are different types of electric generators in construction and size. These different generators can be used for different applications. Mainly generators are planned for generation of electricity and electrical Power for daily life and commercial usage. As we know the electric generator is used in the production of electricity so it can be used for transmission and distribution of power over power lines to commercial, domestic, and industrial use.  

What's alternating current

 What's the alternating current

Current is the flow of electrical charges or electrons in a specific path. When voltage is supplied to a circuit, electric device, the current starts to flow. There are two types of electric current; alternating current (AC) and direct current (DC). These are free electrons in the material that cause to flow and produce current. An alternating current is a current in which periodically reverses its direction and changes its magnitude with time. The polarities and direction of AC quantities like current and voltages change over time. Whereas direct currents(DC) are unidirectional.  It depends upon the supplied voltage that generates DC or AC. Alternating current follows in the sinusoidal waveform. Alternating voltage produces alternating current in the electrical device or circuit. Alternating current is more dangerous than direct current. Ac quantity follows a sine wave with a change in its magnitude over time. Alternating current is easy in the transmission of current through long distances. There are two directions in a sine wave. Upperside is a positive one and lower is negative.

The sinusoidal waveform of alternating current

The direction of alternating current alternates with the time as a sine wave. Whereas the direction of direct current dc is constant during the time. The Alternating current behaves like a wave, the sinusoidal wave is generated by alternating current and voltage. In AC, there is the peak value, RMS value, and some other values that are considered and evaluated in ac quantities. The basic source of dc is the battery but, ac power is distributed and transmitted to residences and businesses. 

Alternating current is used in our home, office, and other places. Almost all our appliances like television, kitchen appliances, fans, and other electrical devices that we use in our daily life operate on alternating currents. Audio and radio signals in electrical wires operate on alternating currents.

Electrical motor and generator can not operate on dc supply, so these are supplied and operated by AC for generating rotation in the coil or shaft. Similarly, in the transformer for transferring electric power from one circuit to another ac power is supplied due to which alternating current is produced in coils of the transformer. The frequency of ac quantity varies time by time. Electrical motors, generators, transformers, and many electrical machines operate on alternating currents and provide us efficient work. In alternating current, there are fewer losses in power than direct current so it is convenient for us and we use it as electricity for transmitting over long distances. 

 Charging of a capacitor

A capacitor is one of the electric components of an electrical circuit or network. A capacitor is a storing device that stores electrical current or voltage in plates.  A capacitor is consists of two parallel conducting plates carrying charges of equal magnitude but in opposite directions, separated by a dielectric medium. 

When voltage is supplied by an electric source to a capacitor, it stores voltage. A capacitor stores voltage until supplied voltage becomes equal to capacitor voltage.  Capacitors are used in electrical network circuits to charge the circuit. Capacitors can be used instead of batteries to charge a circuit or as voltage suppliers.  

The charging of a capacitor depends upon the material of conductor plates, the strength of the dielectric medium between plates, and some other factors. Each material as dielectric has a different strength of charging the capacitors.  The capacity of charging is inversely proportional to the distance between the plates, as distance decreases between plates, the strength of the capacitor to store more charges increases, and vice versa.

 Where the area between plates is directly proportional to the capacitance of the capacitor, as area increases capacity increases. When Capacitor is charged, it can work like a battery to supply voltage to the circuit. While a capacitor is charging by voltage supply, the current is initially high but, decreasing by time as the capacitor is fully charged. 

The capacitance of the capacitor has an inverse relation to the frequency of the voltage source.

The capacitance of the capacitor is the ratio of the charge on the plate and the potential difference between plates.

The S.I unit of capacitance is farad and often picofarad and microfarad are used for the capacitance of the capacitor.

The charge on the capacitor 'Q' is linearly proportional to the potential difference 'V' in the conducting plates of the capacitor.

                    Q~V,   Q = CV or C = Q/V

C=capacity, Q=charge on plate, V=potential difference.

Charging of capacitor

The dielectric medium is capable of supporting the electrostatic forces.

The procedure of charging the capacitor is as the following way.

When the capacitor is connected to the battery, electrons on the left plate in the capacitor are attracted by the positive terminal of the battery and then moves to a right side plate. 

There is an excess of positively charged holes on the left side and an excess of negatively charged electrons.

Capacitors are used in communication apparatus such as VCRs, radios, television, radar, etc. These are can be adjusted by tuning controls. There are a lot of appliances and electronic devices in which capacitors are used such as energy-storing devices and more.

Electromegnatic induction

 Electromagnetic induction

Electromagnetic induction is a fundamental phenomenon between the current-carrying coil of wire and magnetic fields. 

The relative motion between a current-carrying conductor and magnetic field, voltage, or emf(electromotive force) is induced.

 Whenever a coil of wire is brought to a static magnetic field or a stationary coil linked to the varying magnetic field, a change in the magnetic flux produces induced emf.

Electrical current can be generated through a change in magnetic flux in a varying magnetic field. 

The process of electromagnetic induction

Faraday's law of the electromagnetic induction

 An English scientist Micheal Faraday gave the law of electromagnetic induction. 

 Faraday's law of electromagnetic induction states, "an emf or voltage is induced when the magnetic flux changes with time linked to the coil".  

The rate of change of magnetic flux, emf  will be induced

       induced emf = - d/dt magnetic flux

Minus sign shows the Lenz's law

Lenz's law shows the direction of the induced field. The induced voltage or emf is in the opposite direction to flux.

Fleming's right rule is used for the direction of emf, the motion of the conductor, and the magnetic field.

Electromagnetic induction is used to power electrical devices such as electric motors, generators and transformers, and more. 

The source of electromagnetism is the electric current flowing through a coil of wire.

Emf induces when there is relative motion between coil and permanent magnet

Uses

It is used in electrical devices such as electrical generators(hydroelectric dams), electric motors, transformers, etc 

 Where mechanical power is used to move the magnetic field to generate a voltage

Induction motors, current lamp

Loudspeaker, headphones

Magnetic data storing devices VCR, recording tape, hard disk, and more

Electric bells, transformers, and 

The advantages of electromagnetic induction are:

Electrical power(AC or DC) can be generated by using electromagnetic power sources.

There is no need for external electrical sources to produce electrical power.

Working principle of transformer and applications

Working principle and function of transformer

A Transformer is a static(stationary) electrical device by which electrical power is transformed from one circuit to another circuit. It can increase or decrease the voltage in a circuit.

Transformers can be used either to increase the voltage known as stepping up voltage, or it can decrease the voltage known as stepping down the voltage.

To overcome losses, the electricity through the generator passes through a step-up transformer, which increases the voltage. Throughout the distribution system, the voltages are changed using a step-down transformer to decreases the voltages to a suitable application at industries and homes.

  The working principle of the transformer is mutual induction. In transformers, there is no electrical connection between coils. A transformer steps up and steps down voltages. If the number of the primary coil is more than secondary then the transformer will step up voltage otherwise step down voltage if the number of secondary coils is more than the primary coil. Both coils in the transformer are connected magnetically rather than electrically. 

The transformer is based on the principle of mutual induction between two circuits connected by magnetic flux. When current is supplied by supplied Source to the primary coil, magnetic flux is produced, and emf is induced in the secondary coil.

Core type and shell-type both are the types of the transformer.

The transformer consists of two inductive coils which are separated electrically but, linked magnetically through a low reluctance path. Both coils have high mutual inductance.

One coil is connected to a source of alternating voltage, alternating flux is produced in the laminated steel core. The first coil, in which electric energy is fed from the supply is called the primary winding and the other from which energy is drawn out is called secondary winding. The transformer is a device that transfers electric power from one circuit to another, without a change of frequency.  It accomplishes this by electromagnetic induction where the two electric circuits are in the influence of mutual inductance to each other. 

Transformer

A transformer is consists of two coils having mutual inductance and a laminated steel core. These coils are insulated from each other and the steel core.

The number of coils determines whether the voltage is step-up or step-down.

 A transformer is formed from two coils of wire around a magnetic core.

A Transformer work based on Faraday's law of electromagnetic induction and mutual induction.

In transformer electrical power remains constant but, voltage and current vary.

If the current increases, voltage decreases, and vice versa. When an alternating current passes through the primary coil it creates a varying magnetic flux. When the varying magnetic flux is linked with the coil, an E.M.F is induced in the neighboring coil.  A transformer is made up of a rectangular iron core. 

The transformer only works on AC and can't be operated on DC. It operates only on alternating current and voltage.

Applications

The transformer is used as follow:

• To Regulate alternating current,
• To start and stop  the flow of electricity 
• Battery charging 
• Steel manufacturing
• Transmission and distribution lines

• Transformers are used to set apart two circuits electrically and it is used to increase or decrease alternating voltage without changing power in appliances

• It is also used in power generation and distribution of power and, in high-power industrial loads such as motor drives and other appliances. 

• The transformer is also used at the power stations and grid stations through which voltages are supplied to industrial and residential areas.

How does an electric motor work

What is an electric motor?

Electric motors are the fundamental part of doing any machinery work. No machine has to work without motors.

An electric motor is an electrical machine that converts electrical energy into mechanical energy. Electric motors can be powered by direct current (dc) as well as alternating current (AC). When AC or DC voltage is supplied to the electric motor, the shaft rotates.  An electric motor is all about electromagnetism.

Electrical motor

How does an electric motor work

Electrical motors work on the principle of electromagnetism. A motor uses magnets to create motion. As we know that motor converts electrical energy to mechanical energy, so the interaction between the magnetic field and electric current generates a force as torque applied on the moror's shaft.

The electric motor is based on the principle when a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force. Constructionally there is no basic difference between dc motor and dc generator. DC motors are also like dc generators.

The working function of an electric motor

In the motor,  these magnets create rotational motion. Unlike poles of magnets attract such as north and south poles of magnets attract each other and the like poles repel such as north to north or south to south, this attraction and repulsion produced rotation.

This rotational motion creates a force as torque in the motor.

Construction of a basic electric motor

Constructionally, there is no basic difference between dc motor and dc generators. Basic parts of the motor are Armature or rotor, brushes, axle, commutator, permanent magnet, and power source.

When current is supplied to the armature conductor from the power supply, they experience a force tending to rotate the armature. Armature conductor under N-pole of magnet assumed to carry current downward and carry current upward under S-pole. The direction of the force on the conductor can be found by Fleming's left-hand rule. The conductor experience a force as torque that tends to rotate armature in the clockwise or anti-clockwise direction. Reversing the current in the conductor will develop continuous and unidirectional torque.

Structure of electric motor

The working function of the commutator is the same in both the dc motor and dc generator. The commutator assures that the current always flows in one direction. The brushes ride on the commutator. The function of brushes is the transmission of electric current from coil to load in motor.

Applications of electric motor

There are a lot of applications of electric motors because our environment is full of machines and no one can be live without machines that help and facilitates us. 

Almost all the machines operate by electrical motors. There are no machines that do have not an electric motor. Our house, industries, society, and the whole world are full of applications. We can observe by own ourselves the applications of electric motor. 

Some of the applications are as below:

• The electric motor is used in water pumps, drill machines, industrial equipment.

•  There are different machine tools, power tools, fans, compressors, rolling mills, and turbines.

• Spinning machines, lifts, centrifugal pumps

      Winching system, cranes, and elevators.

    

 There are different applications and usage of electric motors concerning the size of the motor and constitutionally, from small machines to huge machines.

PN junction diode and its applications

PN junction diode

A PN junction is an interface between two types of semiconductor material, p-type and n-type. The "p" (positive) side contains an excess of holes while the "n" (negative) side contains an excess of electrons in the outer shells of the electrically neutral atoms there. This allows electrical current to pass through the junction only in one direction. The p-n junction is created by doping, for example by ion implantation, diffusion of dopants, or by epitaxy. If two separate pieces of material were used, this would introduce a  between the semiconductors that would severely inhibit its utility by scattering the electrons and holes. P-N junctions are the elementary building blocks of semiconductor electronic devices such as diodes, transistors, solar cells, and integrated circuits. They are the active sites where the electronic actions of devices take place.

PN junction diode

Forward biased 

When the p-type is connected to the positive terminal of the battery and the n-type to the negative terminal then the p-n junction is said to be forward-biased. In the case of the forward-biased junction, the built-in electric field at the p-n junction and the applied electric field are in opposite directions. When both the electric fields add up, the resultant electric field has a lower magnitude than the built-in electric field. The potential barrier is almost eliminated and the current starts flowing in the circuit. results in a less resistive and narrow depletion layer or region. The depletion region’s resistance becomes negligible when the applied voltage is large. 

Forward biased function 

Reverse biased

When the p-type is connected to the negative terminal of the battery and the n-type is connected to the positive side then the p-n junction is said to be reverse biased. In this case, the built-in electric field and the applied electric field are in the same direction. When the two fields are added, the resultant electric field is in the same direction as the built-in electric field creating a more resistive, thicker depletion region. The depletion region becomes more resistive and thicker if the applied voltage increases and the junction resistance becomes very high and as a result, practically no current flows through the circuit.

Reverse biased function 

Application of a junction diode

• PN junction diode can be used as a photodiode as the diode is sensitive to the light when the configuration of the diode is reverse-biased.

• It is used as a rectifier in many electric circuits and as a voltage-controlled oscillator in varactors.

• It can be used as a solar cell and used in switches digital design.

•  The forward-biased diode is used in LED lighting applications.

• It is used in wave shaping circuits in radar, computers, and other electronic devices.