R. K. Electronics: electrical

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Friday, September 7, 2018

Capacitor

Er. Ramesh Kr. Majhi September 07, 2018 0

A capacitor is circuit element which is capable of storing and delivering finite amount of charges. A capacitor essentially consists of two conducting surfaces (plates) separated by a layer of insulating medium called dielectric. One plate of the capacitor (say A) is positively charged, while the other (say B) has negative charge. The charge stored in a capacitor is proportional to the potential difference between the two plates.

When a capacitor is put across a battery there is momentary flow of electrons from A to B. Hence, a potential difference is established between plates A and B. This transient flow of electron gives rise to charge in current. As the charge on plates goes on increasing the voltage across the capacitor goes on increasing. After sometime the voltage across the capacitor becomes equal to voltage of dc source and charging currents’ i’ becomes zero. If dc source is removed now, the capacitor remains charged if such a charged capacitor is shunted by a resistance it will get discharge and voltage across it becomes zero after some time.

Mathematically, capacitance of capacitor is defined as the amount of charge required to create potential difference (PD) of 1 volt.

i.e. C = Q/V

Ø Q = CV

The capacitance is a measure of the amount of charge a capacitor can store; this is determined by the capacitor geometry and by the kind of dielectric between the plates. For a parallel plate capacitor made up of two plates of area A and separated by a distance d, with dielectric material, the capacitance is given by:

C = ε A / d where ε = εr * εo is permittivity of the dielectric material, εr is the relative permittivity and εo = 8.85x10־¹² F/m or C²/Nm² is the permittivity of the free space. With dielectric material, the capacitance is given by:

C = εo A/d

Note that capacitance has units of farads (F). A 1 F capacitor is exceptionally large; typical capacitors have capacitances in the pF - microfarad range.

Dielectrics, insulating materials placed between the plates of a capacitor, cause the electric field inside the capacitor to be reduced for the same amount of charge on the plates. This is because the molecules of the dielectric material get polarized in the field, and they align themselves in a way that sets up another field inside the dielectric opposite to the field from the capacitor plates. The dielectric constant is the ratio of the electric field without the dielectric to the field with the dielectric:

Note that for a set of parallel plates, the electric field between the plates is related to the potential difference by the equation:

for a parallel-plate capacitor: E = V / d

For a given potential difference (i.e., for a given voltage), the higher the dielectric constant, the more charge can be stored in the capacitor. For a parallel-plate capacitor with a dielectric between the plates, the capacitance is:

Energy stored in a capacitor

The energy stored in a capacitor is the same as the work needed to build up the charge on the plates. As the charge increases, the harder it is to add more. Potential energy is the charge multiplied by the potential, and as the charge builds up the potential does too. If the potential difference between the two plates is V at the end of the process, and 0 at the start, the average potential is V / 2. Multiplying this average potential by the charge gives the potential energy : PE = 1/2 Q V.

Substituting in for Q, Q = CV, gives:

The energy stored in a capacitor is: U = 1/2 C V²

Capacitors have a variety of uses because there are many applications that involve storing charge. A good example is computer memory, but capacitors are found in all sorts of electrical circuits, and are often used to minimize voltage fluctuations. Another application is a flash bulb for a camera, which requires a lot of charge to be transferred in a short time. Batteries are good at providing a small amount of charge for a long time, so charge is transferred slowly from a battery to a capacitor. The capacitor is discharged quickly through a flash bulb, lighting the bulb brightly for a short time.

If the distance between the plates of a capacitor is changed, the capacitance is changed. For a charged capacitor, a change in capacitance correspond to a change in voltage, which is easily measured. This is exploited in applications ranging from certain microphones to the the keys in some computer keyboards.

Playing with a capacitor

To help understand how a capacitor works, we can experiment using a power supply, a capacitor, and a piece of dielectric material. The power supply provides the voltage, or potential difference, that causes charge to build up on the capacitor plates.

With the power supply connected to the capacitor, a constant difference in potential is maintained between the two plates. This results in a certain amount of charge moving on to the plates from the power supply, and there is a particular electric field between the plates. When some dielectric material is inserted between the plates, the field can not change because the potential difference is constant, and E = V / d. To ensure that the field does not change, charge flows from the power supply to the plates of the capacitor. Removing the dielectric causes the charge to flow back to the power supply, keeping the field constant. To summarize, when the voltage is fixed but the capacitance changes, the amount of charge on the plates changes.

On the other hand, if the power supply is connected to the capacitor briefly and then removed, it will be the charge that stays constant. If a dielectric material is inserted between the plates in this case, the field between the plates will be reduced, as will the potential difference. Removing the dielectric increases the field, and therefore increases the voltage.

Electric fields and potentials in the human body

The body is full of electrical impulses, and we can measure these signals using electrodes placed on the skin. The rhythmic contractions of the heart, for example, are caused by carefully timed electrical impulses. These can be measured with an electrocardiogram (ECG or EKG). If the heart is malfunctioning, this will usually produce a change in the electrical activity of the heart, with particular changes corresponding to particular problems. Similar analysis can be done on the brain using an electroencephalogram (EEG).

Click on EKG's and heart arrythmias for a look at how heart arythmias are investigated using EKG's, as well as for a look at a typical electrical signal from a normal heart.

All about Transformer

types of transformer

Er. Ramesh Kr. Majhi September 07, 2018 0

A transformer is an electrical gadget which, by the standards of electromagnetic acceptance, exchanges electrical vitality starting with one electric circuit then onto the next, without changing the recurrence. The vitality exchange typically happens with a difference in voltage and current. Transformers either increments or abatements AC voltage. Transformers are utilized to meet a wide assortment of requirements. A few transformers can be a few stories high, similar to the sort found at a creating station or sufficiently little to grasp, which may be utilized with the charging support for a camcorder. Regardless of what the shape or size, a transformers reason continues as before: changing electrical power starting with one sort then onto the next. There are a wide range of kinds of transformers being used today. This asset will investigate Power Transformers, Auto Transformers, Distribution Transformers, Instrument Transformers, Isolation Transformers, Potential Transformers and Current Transformers.

How Transformers Work

Essential Transformer Design, it is imperative to recall that transformers don't produce electrical power; they exchange electrical power starting with one AC circuit then onto the next utilizing attractive coupling. The center of the transformer is utilized to give a controlled way to the attractive motion produced in the transformer by the present moving through the windings, which are otherwise called loops. There are four essential parts to the fundamental transformer. The parts incorporate the Input Connection, the Output Connection, the Windings or Coils and the Core.

Input Connections - The information side of a transformer is known as the essential side in light of the fact that the fundamental electrical capacity to be changed is associated now.
Output Connections - The yield (o/p) side or auxiliary side of the transformer is the place the electrical power is sent to the heap. Contingent upon the prerequisite of the heap, the approaching electric power is either expanded or diminished.
Winding - Transformers have two windings, being the essential winding and the optional winding. The essential winding is the curl that draws control from the source. The auxiliary winding is the curl that conveys the vitality at the changed or changed voltage to the heap. As a rule, these two loops are subdivided into a few curls with a specific end goal to diminish the formation of motion.
Core - The transformer center is utilized to give a controlled way to the attractive motion produced in the transformer. The center is for the most part not a strong bar of steel, rather a development of many thin overlaid steel sheets or layers. This development is utilized to help dispense with and decrease warming. Transformers for the most part have one of two sorts of centers: Core Type and Shell Type. These two sorts are recognized from each other by the way in which the essential and auxiliary loops are put around the steel center.

Core type - With this compose, the windings encompass the overlaid center.
Shell type - With this compose, the windings are encompassed by the overlaid center.

At the point when an information voltage is connected to the essential winding, exchanging current begins to stream in the essential winding. As the present streams, a changing attractive field is set up in the transformer center. As this attractive field cuts over the auxiliary winding, exchanging voltage is delivered in the optional winding.

The proportion between the quantity of real turns of wire in each loop is the key in deciding the kind of transformer and what the yield voltage will be. The proportion between yield voltage and information voltage is the same as the proportion of the quantity of turns between the two windings.

A transformers yield voltage is more prominent than the information voltage if the optional winding has a greater number of turns of wire than the essential winding. The yield voltage is ventured up, and thought to be a "progression up transformer". In the event that the auxiliary winding has less turns than the essential winding, the yield voltage is lower. This is a "progression down transformer".

Transformer Configurations

There are diverse setups for both single-stage and three-stage frameworks.

Single-phase Power - Single-stage transformers are frequently used to supply control for private lighting, repository, cooling, and warming needs. Single stage transformers can be made much more adaptable by having both the essential winding and auxiliary twisting made in two a balance of. The two sections of either winding would then be able to be reconnected in arrangement or parallel designs.

Three-phase Power - Power might be provided through a three-stage circuit containing transformers in which an arrangement of three single-stage transformers is utilized, or on three-stage transformer is utilized. At the point when a lot of intensity is engaged with the change of three-stage control, it is more sparing to utilize a three-stage transformer. The one of a kind game plan of the windings and center spares a great deal of iron.

Delta and Wye Defined - There are two association designs for three-stage control: Delta and Wye. Delta and Wye are Greek letters that speak to the manner in which the conductors on the transformers are arranged. In a delta association, the three conductors are associated end to end in a triangle or delta shape. For a wye, every one of the conductors transmit from the middle, which means they are associated at one regular point.

Three-phase Transformers - Three-stage transformers have six windings; three essential and three optional. The six windings are associated by the maker as either delta or wye. As already expressed, the essential windings and auxiliary windings may each be associated in a delta or wye design. They don't need to be associated in a similar setup in a similar transformer. The genuine association designs utilized rely on the application.

Power Transformer

A power transformer is utilized principally to couple electrical vitality from a power supply line to a circuit framework, or to at least one segments of the framework. A power transformer utilized with strong state circuits is known as a rectifier transformer. A power transformer's appraising is given as far as the optional's most extreme voltage and current-conveying limit.

Distribution Transformer

A shaft compose dissemination transformer is utilized to supply generally little measures of capacity to habitations. It is utilized toward the finish of the electrical utility's conveyance framework.

Autotransformer

The autotransformer is an extraordinary kind of intensity transformer. It comprises of a solitary, persistent winding that is tapped on one side to give either a stage up or a stage down capacity. This is unique in relation to an ordinary two-winding transformer, which has the essential and auxiliary totally disengaged from each other, however attractively connected by a typical center. The autotransformer's windings are both electrically and attractively interconnected.

An autotransformer is at first less expensive than a correspondingly evaluated two-winding transformer. It likewise has better direction (littler voltage drops), and more prominent proficiency. Moreover, it tends to be utilized to get the impartial wire of a three-wire 240/120-volt benefit, much the same as the auxiliary of a two winding transformer. The autotransformer is viewed as dangerous for use on standard dispersion circuits. This is on account of the high-voltage essential circuits are associated straightforwardly to the low-voltage auxiliary circuit.

Isolation Transformer

A disengagement transformer is an extremely one of a kind transformer. It has a 1:1 turn's proportion. In this way, it doesn't step voltage up or down. Rather, it fills in as a security gadget. It is utilized to confine the grounded conductor of an electrical cable from the frame or any bit of a circuit stack. Utilizing a segregation transformer does not lessen the threat or stun if contact is made over the transformer's auxiliary winding.

In fact, any obvious transformer, regardless of whether used to exchange flags or power, is detaching, as the essential and optional are not associated by conductors but rather just by acceptance. Be that as it may, just transformers whose basic role is to seclude circuits (restricted to the more typical transformer capacity of voltage change), are routinely portrayed as disengagement transformers.

Instrument Transformer

For estimating high estimations of current or voltage, it is alluring to utilize standard low-run estimating instruments together with exceptionally developed instrument transformers, additionally called exact proportion transformers. An exact proportion transformer does similarly as the name proposes. It changes at a precise proportion to enable a connected instrument to check the current or voltage without really running full power through the instrument. It is required to change generally little measures of intensity since it's solitary load, called a weight, is the fragile moving components of an ammeter, voltmeter or wattmeter.

There are two sorts of instrument transformers:

Current - Used with an ammeter to gauge current in AC voltages

Potential - Used with a voltmeter to gauge voltage (potential distinction) in AC.

Current Transformer

A present transformer has an essential curl of at least one turns of overwhelming wire. It is constantly associated in arrangement in the circuit in which current is to be estimated. The auxiliary loop is comprised of numerous turns of fine wire, which should dependably be associated over the ammeter terminals. The optional of a present transformer should never be open-circuited. This is on account of the essential isn't associated with a steady source. There is an extensive variety of conceivable essential voltages, on the grounds that the gadget can be associated with numerous kinds of conductors. The optional should dependably be accessible (shut circuited) to respond with the essential, to keep the center from ending up totally polarized. On the off chance that this happens, the instruments will never again read precisely.

A cinch on ammeter works correspondingly. By opening the brace and putting it around a current conveying conductor, the conductor itself goes about as a solitary turn essential. The optional and the ammeter are advantageously mounted in the handle of the gadget. The dial enables various current extents to be measured precisely.

Potential Transformer

A potential transformer is a precisely composed, to a great degree exact advance down transformer. It is ordinarily utilized with a standard 120-volt voltmeter. By duplicating the perusing on the voltmeter (called the avoidances) by the proportion of change, the client can decide the voltage on the high side. Basic change proportions are 10:1, 20:1, 40:1, 80:1, 100:1, 120:1, and significantly higher.

As a rule, a potential transformer is fundamentally the same as a standard two-twisting transformer, with the exception of that it handles a little measure of intensity. Transformers for this administration are dependably the shell compose, in light of the fact that this development has been demonstrated to give better precision.

Potential Transformers (like the one presented above) are intended for observing single-stage and three-stage control line voltages in control metering applications.

Resistor Color Coding

tricks to learn color code

Er. Ramesh Kr. Majhi September 06, 2018 0

Resistor esteems are regularly shown with shading codes. For all intents and purposes every single leaded resistor with a power rating up to one watt are set apart with shading groups. The coding is characterized in the universal standard IEC 60062. This standard portrays the checking codes for resistors and capacitors. It incorporates additionally numerical codes, as frequently utilized for SMD resistors. The shading code is given by a few groups. Together they indicate the opposition esteem, the resilience and some of the time the dependability or disappointment rate. The quantity of groups changes from three till six. As a base, two groups show the opposition esteem and one band fills in as multiplier. The opposition esteems are institutionalized, these qualities are called favored esteem.

Resistor shading code graph

The graph beneath demonstrates to decide the opposition and resilience for resistors. The table can likewise be utilized to indicate the shade of the groups when the qualities are known. A programmed resistor mini-computer can be utilized to rapidly discover the resistor esteems

Tips for perusing resistor codes:

Technique to remember color code in Nepali: Mr. BBROY le afno Green Ball r Vai ko Granite Weapon Gold sitta Satyo.

In the segments underneath illustrations are given for various quantities of groups, however first a few hints are given to peruse the shading code:

The perusing heading may not generally be clear. Now and again the expanded space between band 3 and 4 give away the perusing bearing. Likewise, the primary band is typically the nearest to a lead. A gold or silver band (the resilience) is dependably the last band.

It is a decent practice to check the maker's documentation to make sure about the utilized coding framework. Shockingly better is to quantify the obstruction with a multi-meter. Now and again this may even be the best way to make sense of the opposition; for instance when the shading groups are singed off.

What are "serial" and "parallel" circuits?

series and parallel circuits

Er. Ramesh Kr. Majhi September 05, 2018 0

As a rule, we discover circuits where in excess of two segments are associated together. There are two essential manners by which to interface in excess of two circuit parts: arrangement and parallel. Initial, a case of an arrangement circuit:

Here, we have three resistors (marked R1, R2, and R3), associated in a long chain from one terminal of the battery to the next. The characterizing normal for an arrangement circuit is that there is just a single way for electrons to stream. In this circuit the electrons stream in a counter-clockwise course, from guide 4 toward direct 3 toward guide 2 toward point 1 and back around to 4.

Presently, we should take a gander at the other kind of circuit, a parallel setup:

Once more, we have three resistors, yet this time they shape in excess of one ceaseless way for electrons to stream. There's one way from 8 to 7 to 2 to 1 and back to 8 once more. There's another from 8 to 7 to 6 to 3 to 2 to 1 and back to 8 once more. And after that there's a third way from 8 to 7 to 6 to 5 to 4 to 3 to 2 to 1 and back to 8 once more. Every individual way (through R1, R2, and R3) is known as a branch.

The characterizing normal for a parallel circuit is that all parts are associated between a similar arrangement of electrically basic focuses. Taking a gander at the schematic outline, we see that focuses 1, 2, 3, and 4 are on the whole electrically normal. So are focuses 8, 7, 6, and 5. Note that all resistors and additionally the battery are associated between these two arrangements of focuses.

Furthermore, obviously, the many-sided quality doesn't stop at straightforward arrangement and parallel either! We can have circuits that are a mix of arrangement and parallel, as well:

In this circuit, we have two circles for electrons to course through: one from 6 to 5 to 2 to 1 and back to 6 once more, and another from 6 to 5 to 4 to 3 to 2 to 1 and back to 6 once more. Notice how both current ways experience R1 (from guide 2 toward point 1). In this arrangement, we'd state that R2 and R3 are in parallel with each other, while R1 is in arrangement with the parallel mix of R2 and R3.

The fundamental thought of an "arrangement" association is that segments are associated end-to-end in a line to shape a solitary way for electrons to stream:

The fundamental thought of a "parallel" association, then again, is that all parts are associated over each other's leads. In an absolutely parallel circuit, there are never in excess of two arrangements of electrically basic focuses, regardless of what number of segments are associated. There are numerous ways for electrons to stream, yet just a single voltage over all parts:

Arrangement and parallel resistor designs have altogether different electrical properties. We'll investigate the properties of every design in the areas to come.

REVIEWS:

• In an arrangement circuit, all parts are associated end-to-end, shaping a solitary way for electrons to stream.

• In a parallel circuit, all parts are associated over each other, shaping precisely two arrangements of electrically regular focuses.

• A "branch" in a parallel circuit is a way for electric current shaped by one of the heap parts, (for example, a resistor).

• Components in a series circuit share the same current: ITotal = I1 = I2 = . . . In

• Total resistance in a series circuit is equal to the sum of the individual resistances: RTotal = R1 + R2 + . . . Rn

• Total voltage in a series circuit is equal to the sum of the individual voltage drops: ETotal = E1 + E2 + . . . En

• Components in a parallel circuit share a similar voltage: ETotal = E1 = E2 = . . . =En

• Total obstruction in a parallel circuit is not as much as any of the individual protections: RTotal = 1/(1/R1 + 1/R2 + . . . 1/Rn)

• Total current in a parallel circuit is equivalent to the aggregate of the individual branch streams: ITotal = I1 + I2 + . . . In.

What is Resistor ?

types of resistor

Er. Ramesh Kr. Majhi September 05, 2018 0

The resistor is a latent electrical segment to make obstruction in the stream of electric current. In

every single electrical system and electronic circuits they can be found. The obstruction is estimated in ohms. An ohm is the obstruction that happens when a current of one ampere goes through a resistor with a one volt drop over its terminals. The current is corresponding to the voltage over the terminal finishes. This proportion is spoken to by Ohm's law:

equation with ohm's law: R=V/I

Resistors are utilized for some reasons. A couple of illustrations incorporate delimit electric current, voltage division, warm age, coordinating and stacking circuits, control gain, and fix time constants. They are monetarily accessible with opposition esteems over a scope of in excess of nine requests of size. They can be utilized to as electric brakes to disperse dynamic vitality from trains, or be littler than a square millimeter for hardware.

Read more https://rktech4engineers.blogspot.com/what-is-a-resistor/

Resistor definition and image

A resistor is an inactive electrical segment with the essential capacity to confine the stream of electric current.

The universal IEC image is a rectangular shape. In the USA the ANSI standard is extremely normal, this is a crisscross line (appeared on the right).

Read more https://rktech4engineers.blogspot.com/what-is-a-resistor/

Fixed resistor symbol Fixed resistor symbol

Outline of sorts and materials

Resistors can be partitioned in development compose and additionally obstruction material. The accompanying breakdown for the sort can be made:

Settled resistors
Variable resistors, for example, the

Potentiometer
Rheostat
Trimpot

Opposition subject to a physical amount:

Thermistors (NTC and PTC) because of temperature change
Photograph resistor (LDR) because of a changing light level
Varistor (VDR) because of a changing voltage
Magneto resistor (MDR) because of a changing attractive field
Strain Gauges because of mechanical load

For every one of these sorts a standard image exists. Another breakdown in light of the material and assembling procedure can be made:

Carbon structure
Carbon film
Metal film
Metal oxide film
Wirewound
Thwart

The decision of material innovation is a particular to the reason. Frequently it is an exchange off between costs, accuracy and different prerequisites. For instance, carbon piece is an extremely old system with a low accuracy, yet is as yet utilized for particular applications where high vitality beats happen. Carbon organization resistors have a body of a blend of fine carbon particles and a non-conductive artistic. The carbon film method has a superior resistance. These are made of a non-conductive bar with a thin carbon film layer around it. This layer is treated with a winding slice to increment and control the obstruction esteem. Metal and metal oxide film are broadly utilized these days, and have better properties for security and resilience. Moreover, they are less impacted by temperature varieties. They are similarly as carbon film resistors developed with a resistive film around a round and hollow body. Metal oxide film is for the most part more sturdy. Wirewound resistors are presumably the most established compose and can be utilized for both high exactness and also high power applications. They are developed by winding an extraordinary metal combination wire, for example, nickel chrome, around a non-conductive center. They are sturdy, exact and can have low obstruction esteem. A weakness is that they experience the ill effects of parasitic reactance at high frequencies. For the most astounding necessities on accuracy and strength, metal thwart resistors are utilized. They are developed by solidifying an extraordinary composite chilly moved film onto a fired substrate.

Resistor attributes

Subject to the application, the electrical architect indicates distinctive properties of the resistor. The main role is to constrain the stream of electrical current; in this way the key parameter is the obstruction esteem. The assembling precision of this esteem is demonstrated with the resistor resilience in rate. Numerous different parameters that influence the obstruction esteem can be indicated, for example, long haul steadiness or the temperature coefficient. The temperature coefficient, generally indicated in high accuracy applications, is dictated by the resistive material and the mechanical outline.

In high recurrence circuits, for example, in radio hardware, the capacitance and inductance can prompt undesired impacts. Thwart resistors for the most part have a low parasitic reactance, while wirewound resistors are among the most noticeably bad. For exact applications, for example, sound enhancers, the electric clamor must be as low as could be expected under the circumstances. This is regularly indicated as microvolts commotion per volt of connected voltage, for a 1 MHz data transfer capacity. For high power applications the power rating is vital. This determines the most extreme working force the segment can deal with without modifying the properties or harm. The power rating is typically indicated in free air at room temperature. Higher power appraisals require a bigger size and may even require warm sinks. Numerous different attributes can assume a part in the outline determination. Cases are the most extreme voltage, or the beat strength. In circumstances where high voltage floods could happen this is an imperative trademark.

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