Electronics Unit 1 PDF

Electronics UNIT 1 What is electronic devices? An electronic devices are the circuits which is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is...

Electronics UNIT 1 What is electronic devices? An electronic devices are the circuits which is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical circuit. Examples of electronics devices What is Electronic Components? Electronic components are the elements of the circuit which help in its functioning the electrical circuit. Electronic components are the basic building blocks of an electronic circuit any electronic system or any electronic device. They can control the flow of electrons in an electronic system or electronic circuit. Electronic components vary from small to big. So that they are easy to carry them from one place to another place. The cost of some electronic components is low and some of them is high. Conti….. Electronic components consist of two or more terminals. When a group of electronic components is connected together in an electronic board such as a printed circuit board (PCB), a useful electronic circuit is formed. Each electronic component in a circuit performs a particular task. They can be classified into two types Active and Passive Components. Basics of Electrical circuit Types of Electronic Components An electrical circuit is an interconnection of Electronic Components. Based on their capability to generate energy these elements are classified into active or passive electronic Components. Electronic Components are classified into two groups: Passive Components Active components Conti… Passive Components Passive components A passive element is an electrical component that does not generate power, but instead dissipates, stores, and/or releases it. They mainly resist, store, or control the flow of electric current or voltage in a circuit without actively amplifying or generating signals. These Passive components belongs to inactive functions of components, these Passive components do not have capacity to amplify the voltage or to rectify the supply. Without these components assembly of electronic circuit is not possible. Conti… Resistors, Capacitors, Inductors are called as passive components. Other Passive components include transformers, diodes, thermistors, varactors, transducers, and many other common components.  Resistors Resistors control the flow of current by offering resistance(The property of a substance which opposes the flow of electric current ) They are used to limit current, divide voltage, and set biasing conditions in electronic circuits. A resistor is a passive two-terminal electrical device that resists the flow of current. It is probably the simplest element in an electronic circuit. It is also one of the most common components as resistance is an inherent element of nearly all electronic circuits. They are usually color-coded. Resistor look like::: Applications of Resistors There won’t be any current flowing in the circuit if there is no resistor present. So, resistors are an essential component of electrical circuits. Some applications and uses of resistor are listed below: Circuit functions Voltage dividers Heating applications Variable resistors Frequency and timing LEDs and transistor Uses of Resistor in a Circuit Resistors are used to control current flow in circuits. This configuration is typically helpful for managing circuit tasks like altering the motor’s speed, the pitch of a musical note, the amplifier’s volume, etc. In electronic circuits, resistors provide a range of functions, such as reducing current flow, regulating signal levels, dividing voltages, terminating transmission lines. Basic terms Voltage is the force that makes electrons flow. Current: Current is the rate of the flow of electrons. Conti…. Uses of Resistor in Voltage Dividers As voltage dividers, resistors are utilised in electrical circuits. A voltage divider is a simple circuit that is used to divide the input voltage into smaller voltage. It is made up of two resistors connected in series, with the output voltage taken across one of the resistors. A voltage divider distributes the source voltage among various electrical circuit components and provides the required operating voltage at the load terminal or output. Conti…. Uses of Resistor in Heating Applications Due to the high temperature, the filament of appliances like heaters, toasters, electric stoves, microwaves, etc. glows. This is because the metal filament acts as a resistor and generates heat when current flows through it. Conti…. Uses of Resistor in LEDs & Transistors LEDs and transistors are examples of semiconductor devices that are sensitive to input current values. As a result, resistors are utilised in the circuit to control the input current value. Uses of Variable Resistor Since the resistance of variable resistors can be adjusted to a certain value, they are frequently employed in electrical circuits to change the value of current or voltage. With variable resistors, you may change the resistance while maintaining a constant current to change the voltage value. Uses of Resistor in Frequency and Timing Devices such as light flashers, electronic sirens, and blinking lights on airplanes or towers operate by storing electrical charge for a specific duration and then releasing it as light. In these cases, the resistor determines the amount of current that flows based on the predetermined time. By increasing the resistance, the discharge time of current in the circuit is prolonged. Uses of Resistor In Daily Life The employment of resistors in heaters, toasters, microwaves, electric stoves, and many other heating equipments is due to the fact that they generate heat when conducting electricity. In the evening, the street lights are automatically turned on, and they are turned off in the daytime. This is because of photoresistors, which allow them to detect light and darkness. In the evening, the street lights are automatically turned on, and they are turned off in the daytime. This is because of photoresistors, which allow them to detect light and darkness. Photo resistor(LDR) LDR (Light Dependent Resistor) as the name states is a special type of resistor that works on the photoconductivity principle means that resistance changes according to the intensity of light. Its resistance decreases with an increase in the intensity of light. It is often used as a light sensor, light meter, Automatic street light, and in areas where we need to have light sensitivity. Look like How are LDRs Made? The Light-dependent resistors made with photosensitive semiconductor materials like Cadmium Sulphides (CdS), lead sulfide, lead selenide, indium antimonide, or cadmium selenide and they are placed in a Zig-Zag shape. Two metal contacts are placed on both ends of the Zig- Zag shape these metal contacts help in creating a connection with the LDRs. Now, a transparent coating is applied on the top so that the zig-zag-shaped photosensitive material gets protected and as the coating is transparent the LDR will be able to capture light from the outer environment for its working. Look like LDR Working Principle It works on the principle of photoconductivity whenever the light falls on its photoconductive material, it absorbs its energy and the electrons of that photoconductive material in the valence band (The valence band is the band of electron orbitals that electrons can jump out of, moving into the conduction band when excited. )get excited and go to the conduction band and thus increasing the conductivity as per the increase in light intensity. Types of Resistor Conti… Linear Resistors The resistors whose value changes with the applied temperature and voltage, are called linear resistors. There are two basic types of resistors with linear properties namely fixed resistors and variable resistors. Fixed resistors Fixed resistors are resistors with a specific value. Fixed resistors one of the most widely used types of resistor. Fixed resistors are used in electronics circuits to set the correct conditions in a circuit. Conti…. Types of Fixed Resistors 1.Wire Wound Resistors 2.Carbon Film Resistors Wire wound resistor Wirewound resistors are constructed using a conductive wire. The conductive wire is then wound around a non-conductive core. The conductive wire can be made of varying alloys and thickness to control the resistance value. Wirewound resistors are typically used in high power and industrial applications such as circuit breakers and fuses. Wire wound register Carbon film resistor A type of carbon resistor that uses carbon film to limit the flow of electric current to a particular level is known as a carbon film resistor. These are fixed value type resistors that are designed out of a ceramic carrier through a thin clean carbon film around it. Here carbon film works like the resistive material. The carbon film resistor symbol looks like a normal resistor Carbon film resistor Conti…. Variable Resistors Variable Resistors consist of a slider which taps onto the main resistor element and a fixed resistor element. A variable resistor is a resistor of which the electric resistance value can be adjusted. Conti….. Types of Variable Resistors 1.Potentiometer: A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. 2.Rheostat: A rheostat is a variable resistor that allows the manual control of the flow of electric current by lowering or raising the resistance. 3.Trimmer Resistor:Trimmers are mechanically driven, variable resistors. A wiper is moved across the resistance element, picking off an intermediate voltage in the potentiometer mode Trimmer resistor How does resistor works? A Resistor works by using this natural property of resistivity/conductivity of any material. It absorbs energy from the flow of electrons (electric energy) and dissipates in the form of heat (thermal energy). How does resistor works? Resistor and Resistance || 3d Animated hindi explanation || Physics|| (youtube.com) Non-Linear Resistor Non-linear resistors are those types of resistors where the electric current flowing through it changes with the exchange in applied voltage or temperature Thermistors Thermistors are a type of variable resistor that notices the change in temperature. Photo Resistor or LDR (Light Dependent Resistors) Photo Resistor or LDR (Light Dependent Resistors) or Photo Conductive Cell is a light-controlled variable resistor. The photo resistor resistance decreases with increase in incident light intensity. Capacitor A capacitor is a two-terminal electrical device that can store energy in the form of an electric charge. It consists of two electrical conductors that are separated by a distance. The space between the conductors may be filled by vacuum or with an insulating material known as a dielectric. The ability of the capacitor to store charges is known as capacitance. Capacitors store energy by holding apart pairs of opposite charges Look like Conti…. An electric field appears across the capacitor. The positive plate (plate I) accumulates positive charges from the battery, and the negative plate (plate II) accumulates negative charges from the battery. After a point, the capacitor holds the maximum amount of charge as per its capacitance with respect to this voltage. This time span is called the charging time of the capacitor. When the battery is removed from the capacitor, the two plates hold a negative and positive charge for a certain time. Thus, the capacitor acts as a source of electrical energy. If these plates are connected to a load, the current flows to the load from Plate I to Plate II until all the charges are dissipated from both plates. This time span is known as the discharging time of the capacitor. What Are the Applications of Capacitors? Capacitors for Energy Storage Audio equipment Camera Flashes Power supplies Magnetic coils Lasers Capacitors for Power Conditioning Improve the quality of power Capacitors allow only AC signals(exhibits both positive and negative values) to pass when they are charged, blocking DC signals(exhibits only positive values or only negative values). This capacitor effect is used in separating or decoupling different parts of electrical circuits to reduce noise as a result of improving efficiency. What Is Alternating Current? An alternating current can be defined as a current that changes its magnitude and polarity at regular intervals of time. It can also be defined as an electrical current that repeatedly changes or reverses its direction opposite to that of Direct Current or DC, which always flows in a single direction Direct Current:In direct current, the voltage is always constant, and the electricity flows in a certain direction. Look like…. Capacitors as Sensors Capacitors are used as sensors to measure a variety of things including humidity, mechanical strain, and fuel levels. Two aspects of capacitor construction are used in the sensing application – the distance between the parallel plates and the material between them. The former detects mechanical changes such as acceleration and pressure, and the latter is used in sensing air humidity. Capacitors for Signal Processing here are advanced applications of capacitors in information technology. Capacitors are used by Dynamic Random Access Memory (DRAM) devices to represent binary information as bits. Look like Types of Capacitors According to structure: 1.Fixed Capacitors(fixed capacitance) 2.Variable Capacitors(variable capacitance) 3.Trimmer Capacitor(A trimmer capacitor differs from a regular variable capacitor in that it's smaller, and its value is set initially during production and is meant to be left there for some time until an adjustment is needed.) Fixed capacitor Trimmer Capacitor Variable capacitor According to polarization: According to polarization: 1.Polarized(capacitors are in use to accomplish high capacitive density) 2.A polarized capacitor is actually a capacitor that can only be used in one voltage direction(DC) 3.Non-polarized capacitors are suitable for both AC and DC supplies. 4.Non-polarized capacitors are capacitors without positive or negative polarity. Voltage is the force that makes electrons flow. Current: Current is the rate of the flow of electrons. Others types…. Ceramic Capacitors(The material in use within this capacitor type is dielectric) dielectric :insulating material or a very poor conductor of electric current. Film Capacitors It consists polymer film, plastic film, or film dielectric. Power Film Capacitors Polypropylene film is in use as a dielectric in a capacitor. Conti….. Electrolytic Capacitors In an electrolytic capacitor, a metallic anode covered with an oxidized layer. It is in use as a dielectric. Paper capacitors: Paper capacitor is a fixed capacitor in which paper is in use as the dielectric material. How does capacitor works? https://www.youtube.com/watch?v=R2QQ0yiqH_U First, we can note that a metal typically has an equal amount of positively and negatively charged particles, which means it’s electrically neutral. Conti…. If we connect a power source or a battery to the metal plates of the capacitor, a current will try to flow, or the electrons from the plate connected to the positive lead of the battery will start moving to the plate connected to the negative lead of the battery. However, because of the dielectric between the plates, the electrons won’t be able to pass through the capacitor, so they will start accumulating on the plate. Cont…. Conti…. After a certain number of electronics accumulated on the plate, the battery will have insufficient energy to push any new electronics to enter the plate At this point, the capacitor is actually fully charged. The first plate has developed a net negative charge, and the second plate has developed an equal net positive charge, creating an electric field with an attractive force between them which holds the charge of the capacitor. Conti…. Capacitor Dielectric Working Principle Let’s take a look how the dielectric can increase the capacitance of the capacitor. A dielectric contains molecules that are polar which means that they can change their orientation based on the charges on the two plates. So the molecules align themselves with the electric field in such a way enabling more electrons to be attracted to the negative plate, while repelling more electrons out of the positive plate. So, once the it is fully charged, if we remove the battery, it will hold the electric charge for a long time, acting as energy storage. Conti…. example Connecting a new capacitor will increase the speed. Capacitors are used to dump a burst of energy to give electric motors a push to help them get spinning Magnetic Field is the region around a magnetic material or a moving electric charge within which the force of magnetism acts. What is an inductor? An inductor is a passive electronic component that temporarily stores energy in a magnetic field when electric current flows through the inductor's coil. In its simplest form, an inductor consists of two terminals and an insulated wire coil that either loops around air or surrounds a core material that enhances the magnetic field. Inductors help to handle fluctuations in an electric current running through a circuit. The inductor's ability to resist changes to the current is referred to as its inductance, which is the ratio of voltage to the current's rate of change within the coil. Inductor look like Conti…. When an electric current flows through a conductor such as copper wire, the current generates a small magnetic field around the wire. If the wire is shaped into a coil, the magnetic field becomes much stronger. If the wire is coiled around a central core made up of a material such as iron, the magnetic field grows stronger still -- this is essentially how an electromagnet works. T The magnetic field completely depends on the electric current. Conti… Inductors use the relationship between the electric current and magnetic field to compensate for changes in the current's flow. When the current begins to pass through the inductor's coil, the magnetic field starts to expand until it finally stabilizes. Until then, the coil inhibits the flow of current. After the magnetic field stabilizes, the current flows through the coil normally. Conti….. energy is stored in the magnetic field as long as the current continues to run through the coil. When the current stops flowing, the magnetic field starts to collapse, and the magnetic energy is converted back into electrical energy, which continues to flow into the circuit until the magnetic field completely collapses. Conti.. Inductance is a result of the induced magnetic field on the coil. It is also determined by several factors, such as The shape of the coil. The number of turns and layers of the wire. The space that is given between the turns. The size of the core. How does inductor works? https://www.youtube.com/watch?v=uW-M8eBHq9U Different Types of Inductors Depending on the type of material used, inductors can be classified as follows: 1.Iron Core Inductor 2.Air Core Inductor 3.Iron Powder Inductor 4.Ferrite Core Inductor, which is divided into: Soft Ferrite Hard Ferrite Iron Core Inductor The core of this type of inductor is made of iron. These inductors are low-space inductors that have high power and high inductance value. However, they are limited in high-frequency capacity. These inductors are used in audio equipment. Iron core conductor Air Core Inductor These inductors are used when the amount of inductance required is low. Since there is no core, it does not have a core loss. But the number of turns the inductor must have is more for this type when compared to the inductors with the core. This results in a high-quality factor. Usually, ceramic inductors are often referred to as air- core inductors. Air Core Inductor Iron Powder Inductor In this type of inductor, the core is iron oxide. They are formed by very fine and insulating particles of pure iron powder. High magnetic flux can be stored in it due to the air gap. The permeability of the core of this type of inductor is very less and is usually below 100. They are mainly used in switching power supplies. Iron Powder Inductor Ferrite Core Inductor In this type of inductor, ferrite materials are used as the core. Ferrites can be classified into two types: soft ferrites and hard ferrites. Soft Ferrite: These are materials that have the ability to reverse their polarity without any external energy. Hard Ferrite: These are permanent magnets, that is, their polarity will not change even when the magnetic field is removed. Ferrite inductor Functions of an Inductor Inductors can be used for two primary functions: 1.To control signals. 2.To store energy. Conti…. Controlling Signals Coils in an inductor can be used to store energy. The function of the inductor depends upon the frequency of the current passing through it. That is, higher frequency signals will be passed less easily and vice versa. This function tells that it blocks AC Current and passes DC Current. Hence, it can be used to block AC signals. Storing Energy Inductor stores energy in the form of magnetic energy. Coils can store electrical energy in the form of magnetic energy, using the property that an electric current flowing through a coil produces a magnetic field, which in turn, produces an electric current. In other words, coils offer a means of storing energy on the basis of inductivity. Semiconductors Semiconductors are materials which have a conductivity between conductors (generally metals) and nonconductors or insulators (such as most ceramics). Conductors are those substances through which electricity can flow are called conductors. Some common conductors are copper, aluminum, gold, and silver. Insulators are those substances through which electricity cannot flow are called insulators. Some common insulators are glass, plastic, rubber, and wood. Why is called semiconductor? A semiconductor is a material that has electrical resistance more than conductors and less than insulators so that it can conduct current not as fast as conductors but does not restrict the flow of current as insulators. So it kind of “semi” conducts the current. Working of semiconductor through video https://www.youtube.com/watch?v=8LUL2cBoJ48 How does semiconductor works? Carbon, silicon and germanium (germanium, like silicon, is also a semiconductor) have a unique property in their electron structure -- each has four electrons in its outer orbital. This allows them to form nice crystals. The four electrons form perfect covalent bonds with four neighboring atoms, creating a lattice. A covalent bond is formed by the equal sharing of electrons from both participating atoms. The pair of electrons participating in this type of bonding is called a shared pair or bonding pair. Covalent bonds are also called molecular bonds. Look like Conti… In a silicon lattice, all silicon atoms bond perfectly to four neighbors, leaving no free electrons to conduct electric current. This makes a silicon crystal an insulator rather than a conductor. Why metals are good conductors of electricity? Metals tend to be good conductors of electricity because they usually have "free electrons" that can move easily between atoms, and electricity involves the flow of electrons. While silicon crystals look metallic, they are not, in fact, metals. All of the outer electrons in a silicon crystal are involved in perfect covalent bonds, so they can't move around. A pure silicon crystal is nearly an insulator -- very little electricity will flow through it. Doping Silicon You can change the behavior of silicon and turn it into a conductor by doping it. In doping, you mix a small amount of an impurity into the silicon crystal. There are two types of semiconductor materials on the basis of impurities: 1.Intrinsic semiconductors 2.Extrinsic semiconductors N-type P-type N-type In N-type doping, phosphorus or arsenic is added to the silicon in small quantities. Phosphorus and arsenic each have five outer electrons, so they're out of place when they get into the silicon lattice. The fifth electron has nothing to bond to, so it's free to move around. It takes only a very small quantity of the impurity to create enough free electrons to allow an electric current to flow through the silicon. N-type silicon is a good conductor. Electrons have a negative charge, hence the name N- type. P-Type In P-type doping, boron or gallium is the dopant. Boron and gallium each have only three outer electrons. When mixed into the silicon lattice, they form "holes" in the lattice where a silicon electron has nothing to bond to. The absence of an electron creates the effect of a positive charge, hence the name P-type. P-type silicon is a good conductor. Applications of semiconductor devices They are used in the designing of logic gates and digital circuits. These are used in microprocessors. They are also used in analog circuits such as oscillators and amplifiers. Used in high voltage applications. diagram Types of Semiconductor devices Diode : Light Emiting Diode(LED) Photo diode: Zener diode LCD : solar cell Diode A diode is a semiconductor device that comprises a single p-n junction. P-n junctions are usually formed by joining up of p-type and n-type semiconductor materials. This formation is due to the reason that the n-type region has a higher number of electron concentrations whereas the p-type region has a higher number of hole concentrations, hence, the electrons get diffused from the n-type region to the p-type region. Hence, this phenomenon is used in generating light. Diode, an electrical component that allows the flow of current in only one direction. In circuit diagrams, a diode is represented by a triangle with a line across one vertex. Uses of diodes Diodes help in performing digital logic. They are used for isolating signals from a supply They are also used in creating power supplies and voltage doublers. The light emitting diodes or LEDs are used in sensors and also in laser devices any many other light illumination devices. Zener diodes are used as voltage regulators. Working of diode In the N-type region, the majority of charge carriers are electrons and the minority of charge carriers are holes. Whereas, In the P-type region, the majority of charge carriers are holes and the minority of charge carriers are electrons. Because of the concentration difference, the diffusion takes place in majority charge carriers and they recombine with the minority charge carriers which are then collected near the junction and this region is known as the Depletion Region. Unbiased pn junction Video working of diode https://www.youtube.com/watch?v=qu9reCzzrco Reverse Bias condition When the anode or p-type terminal of the diode is connected with a negative terminal of the battery and the n-type or cathode is connected with the positive terminal of a battery, this type of connection is called a Reverse Bias condition. Look like Importance of reverse bias Positive terminal attracts the electrons away from the junction in N side and negative terminal attracts the holes away from the junction in P side. As a result of it, the width of the potential barrier increases that impedes(delay) the flow of majority carriers in N side and P side. What is the importance of forward bias? It decreases the potential barrier strength in the circuit. Forward bias has a very thin depletion layer compared to reverse bias. It minimises the circuit resistance, increasing the current flow. Forward Bias Condition When the anode or p-type terminal of the diode is connected with a positive terminal and the n-type or cathode is connected with the negative terminal of the battery, this type of connection is called a Forward Bias condition. Look like LED A light-emitting diode (LED) is a semiconductor device that emits light when an electric current flows through it. When current passes through an LED, the electrons recombine with holes emitting light in the process. LEDs allow the current to flow in the forward direction and blocks the current in the reverse direction. Look like Conti… Light-emitting diodes are heavily doped p-n junctions. Based on the semiconductor material used and the amount of doping, an LED will emit coloured light at a particular spectral wavelength when forward biased. As shown in the figure, an LED is encapsulated with a transparent cover so that emitted light can come out LED Symbol Simple LED Circuit :The circuit consists of an LED, a voltage supply and a resistor to regulate the current and voltage. How does LED work? https://www.youtube.com/watch?v=tPFI2_PdCYA Valence band:The valence band is simply the outermost electron orbital of an atom of any specific material that electrons actually occupy Conduction band: The conduction band is the band of electron orbitals that electrons can jump up into from the valence band when excited. When the electrons are in these orbitals, they have enough energy to move freely in the material. This movement of electrons creates an electric current. Working of LED Conti… EXPLANATION IN THE FORWARD BIAS THE FLOW OF CURRENT in the battery will be from +ve to –ve but the flow of electron will be from –ve to +ve. Due to external voltage when the potencial barrier break the electron will move from n type to p type(higher energy level to lower energy level). Due to this energy difference the light will be emit in the form of photons. At the end…. The energy is released in the form of photons on recombination. In standard diodes, the energy is released in the form of heat. But in light-emitting diodes, the energy is released in the form of photons. We call this phenomenon electroluminescence. Electroluminescence is an optical phenomenon, and electrical phenomenon where a material emits light in response to an electric current passed through it. As the forward voltage increases, the intensity of the light increases and reaches a maximum. Difference between depletion layer and forbidden energy gap 1.The gap between the valence band and the conduction band is referred to as the forbidden gap. 2.The difference in energy levels between the conduction band and valence band is known as the forbidden energy gap. 3.No electron stays in the forbidden band. The depletion region is a region near the junction of a semiconductor device where there are no free charge carriers. In this region, the forbidden energy gap plays a role in creating a potential barrier that prevents the flow of What is the difference between depletion layer and barrier potential? Potential barrier : The potential difference established across the p-n junction due to diffusion of electrons from n-region to p-region is called potential barrier. Depletion region : It is a layer created around the p-n junction which is devoid of free charge carriers and has immobile ions only. What determines the colour of an LED? The colour of the light emitted by the LED depends on the wavelength of the light which in turn depends on the semiconductor material used in the diode while manufacturing LED. Aluminium alloys are used to obtain red, orange and yellow light, and indium alloys are used to get green, blue and white light. Slight changes in the composition of these alloys change the colour of the emitted light. Alloys: Photo diodes: Photodiodes are a class of diodes that converts light energy to electricity. Their working is exactly the opposite of LEDs which are also diodes but they convert electricity to light energy. Photodiodes can also be used in detecting the brightness of the light. Photodiodes are designed to work in reverse bias condition. Typical photodiode materials are Silicon, Germanium and Indium gallium arsenide. They are also called a photo-detector, a light detector, and a photo-sensor diagram Cont… Zener Diode A Zener Diode, also referred to as a breakdown diode, is a specially doped semiconductor device engineered to function in the reverse direction. When the voltage across a Zener diode’s terminals is reversed and reaches the Zener Voltage (also known as the knee voltage), the junction experiences a breakdown, allowing current to flow in the opposite direction. This phenomenon, known as the Zener Effect, is a key characteristic of Zener diodes. In this condition when the electric field increases to a high value it enables the tunnelling of electrons from the valence band to the conduction band of a semiconductor, which suddenly increases the reverse current. Why Zener diode? Conti…lot of heat generated… Conti… Conti… Conti… In reverse the voltage across Zener diode will remain constant even though the current changes, due to this property it is used as voltage regulator. V-I characteristics Look like Applications and Uses of Zener Diode can be seen in the following: Zener diode acts as a voltage regulator Zener diode protects from over voltage When the input voltage increases and reaches the Zener breakdown voltage, the current through the diode will create a voltage drop across the resistor. This triggers a short circuit to the ground. Zener diode is used in clipping circuits Clipper circuits are used to prevent the output signal from going beyond a determined value without changing anything of the input signal. Zener diode can be used to shift voltage Zener diode’s core uses include converting a signal from one voltage to another. What is the Full form of LCD? The full form of LCD is Liquid Crystal Display. it is a passive device, which means that it does not deliver any light to display characters, animations, videos, etc. LCD uses fluorescent tubes to lighten the picture. It is a flat panel display technology, mainly used in TVs and computer monitors, nowadays it is used for mobile phones also. These LCDs are completely different from that old CRT displays, it uses liquid crystals instead of cathode ray in its primary form of operation. LCD In LCD display, it consists of millions of pixels made of crystal and arranged in a rectangular grid. In LCD it has backlights that provide light to each pixel. Each pixel has a red, green, and blue (RGB) sub-pixel that can be turned on or off. Conti… LCD is a combination of two states of matter, the solid and the liquid. The solid part is crystal and the liquid and crystal together make the visible image. LCD consists of two layers which are two polarized panels- filters and electrodes. LCD screen works by blocking the light rather than emitting the light. There are two types of pixel grids in LCD: Active Matrix Grid– It is a newer technology. In smartphone with LCD display uses this technology. Passive Matrix Grid– It is an older technology. Characteristics of LCD Resolution: LCD is made up of liquid crystal, which is neither liquid nor solid, and this thing reflects the light in a well-formed way, lights enter into the crystal and reflect very clearly. So the image made with this liquid crystal is very accurate. Brightness: Brightness means the light provided by the LCD, which is nothing but the intensity of visible light, Contrast Ratio: It is the ratio of the brightest color and the darkest color for a particular position of the screen provided by the display. Response Rate: Response Rate is high in LCD, it means the time required for changing colors of the pixels is very much less Working principle of LCD Polarized light and Unpolarized light The light waves which travel only in a single plane are known as polarized light waves. The process of transforming unpolarized light waves to polarized light waves is called the polarisation of light. Conti…. Advantages of LCD : The main advantage of LCD is, it has low in cost and energy efficient and very less power consumption. LCD is thinner and lighter and very flexible. LCD provides excellent contrast, brightness and resolution, so the picture quality is very clear like a crystal. Radiation of LCD monitors are much less than CRT monitors. It provides various conveniences like portability as compared to previous technology based screens. Solar cell A photovoltaic (PV) cell, commonly called a solar cell, is a nonmechanical device that converts sunlight directly into electricity. Some PV cells can convert artificial light into electricity. It is a form of photoelectric cell, defined as a device whose electrical characteristics, such as current, voltage, or resistance, vary when exposed to light. Solar cells are the building blocks of photovoltaic modules, otherwise known as solar panels. Applications of solar cells They are used as a photodetector detecting light or other electromagnetic radiation near the visible range, measuring light intensity. Solar cells are often bundled together to make larger units called solar modules, themselves coupled into even bigger units known as solar panels. Just like the cells in a battery, the cells in a solar panel are designed to generate electricity; but where a battery’s cells make electricity from chemicals, a solar panel’s cells generate power by capturing sunlight instead. How does a Solar Cells work? A solar cell is a sandwich of n-type silicon and p-type silicon It generates electricity by using sunlight to make electrons hop across the junction between the different flavors of silicon 1.When sunlight shines on the cell, photons (light particles) bombard the upper surface. 2.The photons (yellow blobs) carry their energy down through the cell. 3.The photons give up their energy to electrons (green blobs) in the lower, p-type layer. 4.The electrons use this energy to jump across the barrier into the upper, n-type layer and escape out into the circuit. 5.Flowing around the circuit, the electrons make the lamp light up. Video(how does solar cell works?)