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]]>The transformers, loads, motors and other electrical equipment in power systems are all at different voltage levels.To relate the voltage, power and current ratings of these devices the per-unit system is used. In this system voltages, currents, powers, impedances are not measured in ordinary units volt, amperes etc. Instead, a base value of the quantity is introduced and the actual value is divided by that specific value of archive pu values.

Mathematically: Per Unit value = Actual Value / Value of Quantity

A condenser is an essential part of Steam Power Station which condenses the steam coming from the turbine. Two types of condensers include the Jet condenser and the surface condenser.

A jet condenser is a comparatively economical method in which the steam is mixed with cooling water.

In surface condenser a bank of horizontal tubes which carry the cooling water. Exhausted steam moves over the surface of tubes. Steam loses its heat to water and condenses. Compared to the jet condenser, this method is expensive initially.

Heating is a fatal problem in Power Transformers. It causes burning of the winding. Engineers in Power Industry fight the heat problem by ensuring good design. The core features of the good design involve the reduction of eddy currents. Furthermore, the core and winding of transformers are submerged in oil. Heat from windings and core is transferred to oil. Radiator tubes on outside transformers provide a flow path to transformers heat.

The terms tariff refers to the rate of electrical power (electricity). Most common types of the tariff are:

- Simple Tariff: Each unit of energy is charged at fixed rate.
- Flat rate tariff: In this, the consumers are divided into different classes based on the type of load they use.
- Block rate tariff: The units of energy are divided into different blocks and are charged accordingly. For example consumers using units b/w 1-50 kW are charged at $0.5, consumers utilising 50-100 kW are charged at $0.3 and so on.
- Two part tariff: In this type, two factors are considered for assigning tariff. The first one is maximum demand and the second one is the number of units used.

- HVDC transmission uses two conductors for power transmission, which is comparatively economic as compared to HVAC power system which uses three conductors.
- There is no inductance/capacitance associated with HVDC Power and due to this better voltage regulation is achieved at the consumer end.

Different types of phase faults on Power Systems are:

- L-L: Line to Line Fault
- L-G: Line to Ground Fault
- L-L-G: Line to Line to Ground
- L-L-L: Line to Line to Line

L-L-L is the most dangerous type of phase fault.

It is a ratio between the sum of individual maximum demands to the maximum demand on the power station.

Mathematically,

Diversity Factor = Sum of individual maximum demand / Maximum demand at power station

Since D.F is inversely proportional to Maximum demand, greater D.F means lesser maximum demand and a smaller plant capacity. The above all scenario means that if D.F is greater than capital investment on the plant is smaller.

The combination of the aluminium conductor with steel results in another conductor whose tensile strength is high as compared to individual aluminium itself. This composite conductor is named as aluminium conductor steel reinforced (A.C.S.R)

A transformer which is used to control the voltage levels of the transmission line at a point that is far away from the main transformer. For that purpose, a special type of transformer is used which is named as Booster transformer.

A switc gear contains circuit breakers, switchbusbarsbars, instrumentation transformers and relays.

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]]>V ∝ I

Where ‘V’ is voltage and ‘I’ is current and ‘R’ is constant of proportionality.

R is actually resistance of conductor which is assumed constant.

Removing this proportionality we get:

V = IR

We can use this formula to find current and resistance as well:

I = V/R

and R = V/I

You can easily memorize the above equations from the triangle.

- Draw a triangle.
- Divide it into 3 parts
- Mention V on top side
- Mention I on bottom left side
- Mention R on bottom right side.
- To find V place your thumb on V and observe I and R. Here we get equation IR or better I.R
- To find I place your thumb on I and observe V and R. Here V is in numerator and R is in denominator we get equation I = V/R
- Finally, place your thumb on R and observe V and I. We get R = V/R

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]]>The post Laplace Transform Quick Reference Table [Ohmic References] appeared first on Ohm's Law.

]]>This article shares the Laplace Transform Quick Reference table for commonly used functions.

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]]>The post Decimal-Binary Quick Reference Table [Ohmic References] appeared first on Ohm's Law.

]]>Computers, mobiles and electronic devices work on the binary. The binary system has two numbers 0 and 1. should know both these

Electrical Engineering should know both methods of expressing numbers. The quick reference table below provides information and conversions for both systems.

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]]>

List of Components

- Solar Panel
- Battery Regulator
- Battery
- Inverter

The solar panel is a combination of solar cells. Solar cells are also known as photovoltaic cells (PV cell). The size of single cell ranges between 6-6.5 (square inches). The thickness of the whole cell is same as a page.

Note: *The working principle of solar cells is a part of technical scientific knowledge and you can simply skip this part if you’re more concerned with physical knowledge and working.*

The PV cell has two regions, namely the p and n regions. A pn junction is formed between them. The n region is very thin and allows sunlight to penetrate through it. Whenever sunlight photons penetrate any region (n or p), it strikes the atoms near pn junction and knocks an electron out of valence shell.

The electron leaves the atom, creating a hole behind. Finally, the electron-hole pairs are generated.

After formation of electron-hole pairs, the free electrons in p region move towards n region under the action of electric field and holes in the n region move towards p region.

On connecting load with the panel, these electrons start moving from negative terminal towards the load and then back to the positive terminal. From there, these again pass through pn junction and back to n region. Meanwhile, the sunlight creates new electron-hole pairs and the process continues.

Typically the size of solar cell ranges between 6-6.5 square inches. A single cell can approximately produce 0.5V. The terminal voltage is slightly dependent on sunlight. Change in sunlight’s intensity has a mere change on output voltages.

However the amount of current depends on the intensity of sunlight.

A single cell provides 0.5V on output. Due to this reason, a single cell is impractical. A combination of multiple solar cells in series can solve our problem.

Solar panels are available in 12V, 24V, 36V, 48V, 96V and 120V. One can also get a custom made panel depending on his specific applications.

A battery regulator controls the rate of electric current flowing to the battery. It is also known as charge controller/charge regulator. A charge controller takes the output from the panel and ensures that battery is properly getting a charge. In simple words, a regulator acts as a safety device against over charge.

A solar panel generates DC voltage. Batteries also store this DC voltage. On the other hand, electrical components and devices at our homes require ac voltage. An inverter changes stored DC to ac. For example a standard inverter converts 12V DC to 12V AC.

A transformer steps up the 12 Vac to 120Vac. Usually, transformers and inverter circuit is assembled inside the same box.

Solar panels require deep cycle Lead acid batteries. A deep cycle battery is deeply discharged whilst by using most of its capacity. Moreover, these batteries can be recharged thousands of times and are also available at lower cost.

For the same ratings lithium-ion battery costs double than a Lead acid battery.

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]]>After reading this post you will be able to learn:

- Different types of Resistors
- Difference between Potentiometer and Rheostat
- Resistor Color Codes
- Prefixes
- Size of Components and its relationship with wattage rating

The ability of resistor to current flow is known as resistance. SI unit of resistance is ohms.

Various types of resistors are used in different electrical applications. All these types, however, fall in one of these two categories: The fixed resistors and variable resistors.

FRs have a constant value of resistance. This value always remains the same within the tolerance levels. The carbon composition models are inexpensive and easily available. However, they have a large range of tolerance usually ranging between 2-10%.

Other FR models include metal film and metal oxide resistors. Both these models have very small tolerance value and they provide highly precise values. The cons of such model, however, is their high price.

Wire wound resistors is another class of FRs. These models can be employed when a large amount of heat is present and normal FRs are expected to die.

As the name explains, VRs provide a variable resistance. VRs have three terminals. This section provides information on two different models of VRs.

The generic potentiometer is also known as the classic potentiometer. Its usual size ranges between 1-1.5 inches. A wiper (knob) is attached on GPs which can be adjusted for changing resistance.

TPs can be thought of as a modern class of GPs. TPs require a screw drive for adjusting the value of resistance.

The working of GPs and TPs is exactly similar. There are two working modes: As Potentiometer and as Rheostat

In this configuration, the terminals b,c connect with an external circuit for providing variable resistance. The knob/setting of the component can be adjusted to change the value of resistance. Change in resistance changes the output voltage.

Two connections a and b join with an external circuit. The knob/settings can be adjusted to change the value of resistance. The change in resistance changes the amount of current flowing through the circuit.

In other words, the potentiometer mode can be thought of as a variable voltage providing device and rheostat mode can be though as a variable current providing the device.

Photoresistor: It is a light controlled VR whose value of resistance (VOR) decrease with the increase in the intensity of light.

Thermistor: The temperature dependent VR whose VOR changes with a change in temperature. Thermistors are classified in two classes: NTC and PTC.NTC stands for negative temperature coefficient

NTC stands for the ** negative temperature coefficient** thermistor and resistance of such components decrease with increase in temperature.

PTC stands for the * positive temperature coefficient* thermistor and r of such devices increases with increase in temperature.

Resistors are measured in ohms (Ω) and they could have a very small value like 1Ω or a very large value such as 10,00,000Ω. In scientific work, the notation large numbers like 10,00,000 are raised to the power of 10. For example, we can write 10,00,000 as 10^{5}. In Electrical Engineering the prefixes are used instead. For example, 10,00,000 can be expressed as 1 Mega ohm (1MΩ). A list of most commonly used prefixes is provided here for sake of reference. You can also use a prefixes calculator for conversions.

The tolerance and resistance values of Wire wound and power resistors are printed over their bodies. On the other hand, small sized resistors such as Carbon and metal film resistors have circular bands printed over their bodies. The number of bands on resistors can be 4, 5 or 6.

The first band represent the first and second digit of value. The third band is multiplier and value obtained from first and second are multiplied with this band. The fourth and last one represents tolerance value. The tolerance value is a range of values within which the resistance can oscillate.

Example: 5kΩ ±5%.

The first band was Green which provides first value 5, the second band was black which provides second digit 0. The third one is a red multiplier of 100. This says 50 * 100 = 5kΩ and finally a tolerance of ±5%.

The 5 Band code is same to 4 with a difference in an extra value.

You can use these both charts or can use the following calculator for finding values directly.

However, there are 7 Different values which you should memorise.

The size of resistors depends on the power rating. The figure below gives a comparative analysis of size and wattage rating:

So that was all about our Ohmic Guide. Hope you enjoyed it and learn a lot from it. Please share your views in comments.

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]]>The post 5 Practical Applications of Ohm’s Law in Daily Life appeared first on Ohm's Law.

]]>The electrical heater is a commonly used appliance in winters. Provided with the resistance of heater coil and applied voltage, We can calculate the power supplied to this heater. Let’s assume that resistance of heater coil is 5 ohm and input voltages are 120V. We can use the formula from Ohmic Wheel: P = V^{2}/R to find the power, P = 120^{2}/5 ohm = 2880 watt. This power can then be multiplied with time to calculate the electricity bill at our premises.

The speed control of conventional fans is achieved by using a potentiometer. A potentiometer is a variable resistance. A circular knob on the component can be rotated to achieve a variable resistance on the output terminals. For any specific value of input, we can calculate the resistance, current and thus power flowing through Ohm’s Law.

Most electronic devices in our daily life such as Mobile phone chargers, Laptop chargers, Internal circuits of devices and DC Power supplies all require a specific amount of current. Using Ohm’s Law we can calculate the amount of resistance that would be connected in that circuit for achieving any specific value of current.

Fuses and circuit breakers are the protection components which connect in series with the electronic devices. Fuses/CB’s are usually rated in Amperes. The selection of fuse for any specific rating of the component is calculated by Using Ohm’s Law. For example, you have an electric kettle which has an internal element of 10 ohms. The applied voltages are 100V. Now using Ohm’s law the current comes out to be I = V/R = 100V/10 ohm = 10A. Now while designing Fuse you are required to keep the rating at 10A.

Same as above.

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]]>The post 7 Most Commonly Used Resistor Bands you Should Memorize appeared first on Ohm's Law.

]]>But,

It is a silly practice to calculate the same value again and again.

Why not use our BRAIN automation for that purpose?

Here is the collection of 7 most commonly used Resistor Bands you should memorize.

Brown Black Brown Gold

Yellow Violet Brown

Brown Black Red Gold

Red Red Red Gold

Yellow Violet Red Gold

Brown Black Orange Gold

So that was all about our collection. Here is the summarised save button for your reference.

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]]>

It is defined as the potential difference between two points.

The concept of voltage can be easily understood by comparing magnetic forces of material with electrical forces. We all are familiar with the simple magnet and its magnetic property by which it attracts some metallic objects towards itself. A magnet has the magnetic force which surrounds its core and it attracts every other object which is placed inside its field. The magnetic forces are strong near the magnet and they begin to weak while we move away from that magnet.

Like a magnetic force, there is a similar force which is named as the Electric force (EF). Like the previous case of magnets, EF is strong at some points, and it is weak at other points. The comparative difference of Electric force between weak and strong points is known as potential difference. Technically the name ‘Voltage’ represents this potential difference which exists between different points.

The flow of charges from one point to another.

Electrical conductors contain a large number of electrons. The application of voltage source (potential difference) across any conductor causes the flow of electrons from lower to the higher terminal.

Two different conventions represent the flow of charges from one point to another.

In old days the scientists though that flow of charges from positive to the negative terminal is responsible for the current flow. (In real the case is opposite). However, the trend is still followed today and this type of flow is known as conventional current flow.

The flow of electron from -ve to +ve terminals is responsible for the flow of current. This type of flow is known as Electron current flow.

We previously studied that moving electrons are responsible for producing current in any circuit. These moving electrons continuously collide with the static atoms and electrons present in the atom. A quantity resistance represents this opposition offered by static atoms and electrons. In simple words, we can describe the resistance as an opposition force which tends to reduce the current flowing through any circuit.

Resistors are the practical components which provide resistance.

The ability of anybody to do work is known as Power.

In Electrical terms, it can be defined as the transfer of energy per unit time. Mathematically we can explain it as the current times voltage.

P = VI

The above discussion along with the units of quantities can be summarised in this graphic:

Power, Current, Voltage and Resistance are the four basic Electrical quantities that help us to understand What exactly Electrical is and what are we going to study.

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]]>The post Ohm’s Law Circuit Diagram with 5 Different Examples appeared first on Ohm's Law.

]]>Two parallel lines having one with comparatively larger length represents the DC Source and a Zig-Zag symbol represents the resistor. Whereas the simple lines are used to represent the wires.

Now let’s start learning the basic mathematics of law using 10 Different Examples.

Example 1: A 10V battery connects in series with a 20k ohm Resistance. Find the current flowing through the circuit.

Solution: Using V_{1} = I_{1} R_{1}.

I_{1} = V_{1}/R_{1} = 0.5 mA

Example 2: A 15V source connects with an unknown resistor. The value of current is measured as 5 mA. Find the value of R.

Solution: R_{2}= V_{2}/ I_{2 }= 15V / 5mA = 3kΩ

Example 3: A 50k Resistor joins with a 25VDC Variable Supply. Find the value of unknown current that is flowing through this circuit.

Solution: I_{3} = V_{3} / R_{3} = 25V / 50k = 0.5mA

Example 4: The power dissipation through a 29k Resistance is 15watt. Find the value of current and input voltages supplied by the source.

Solution: Here the formulas: I = SQRT(P/R) and V = SQRT(P*R) will be used. You can learn about all these formulas from Ohmic Wheel.

Example 5: R5 = 10Ω and P5 = 20watt

Solution: V5 = 14.14 and I5 = 1.414

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