What is a superconductor?

A superconductor is an element or metallic alloy which, when cooled below a certain threshold temperature, completely loses all its electrical resistance. Thus, superconductors can allow electrical current to flow without any energy loss due to ideally zero resistance. But in practice, an ideal superconductor is very hard to manufactured. Hence very high conductivity materials made by the above principle, so named as superconductors. There are huge applications of superconductors.

 Superconductors are indeed perfect conductor that has zero resistance. It doesn’t just have very low resistance and conducts electricity well, but it has absolutely ZERO resistance and conducts electricity perfectly with no losses at all. In theory if you had a super conductor material it could be infinitely thin and infinitely long. Imagine a thin strand of 30 gauge wire carrying all the electricity used in the USA. That is possible with a super conductor.

Super conductor behavior is typically seen only near absolute zero which is really cold at -273 degrees centigrade which is 460 degrees below zero Fahrenheit. Better put on your long underwear for that. Minor detail, you can get close to absolute zero but so far it’s been impossible to get all the way to absolute zero. Fortunately some materials become super conductors at achievable temperatures that are slightly above absolute detail.

So why haven’t we seen super conductors in practical applications? Well, you need an electrical insulator and you need a thermal insulator around the super conductor. So far there isn’t much luck finding a perfect insulator, so a little heat leaches through any insulation, so must continually cool the material. You can cool a super conductor material in the lab but it isn’t practical across spans of distances like power lines. As usual, the devil is in the detail.

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Black holes | Definition, formation, and facts

Througout the field of cosmology, black holes has stood out to be among the most fascinating things ever studied about our universe.  The idea that a super massive and dense object exist in space where  gravity pulls so strong that it crushes and sucks anything across is path has continued to marvel astronomers and astrophysicists over the past years. Most famously, the winners for the 2020 noble prize award in the physics categories were all involved in various discoveries about  black holes.

So one may ask, what's really a black hole and how does it work?

Definition of a black hole

A black hole is a region in space where the force of gravity  pulls so strong that it prevent the escape of even the fastest of particles. Not even electromagnetic radiation such as light  can escape  it. 

A black hole's gravitational pull is so intense that no matter of any form can escape it once inside a certain region, called the event horizon.

So why are they called "black holes" anyway?

Ironically, black holes are not inherently black, neither are they conical spinning holes in the universe as some images may depict. The facts remains that the gravitational pull being experience on a black holes is so strong that it ends up crushing and sucking(like a hole), any matter found near it surrounding, including any rays of light.  When all light rays directed at a black hole are all sucked up to the last photon, what will be left is total darkness at the center. That is why black holes are often depicted as black looking monster tonadoes in space. 

So a clear answer to why black holes are so named is simply because:

"on a black hole, gravity pulls so extreme that it ends up sucking(like a hole) any matter found near it territory, including any traces of light rays, making it appear as black at the center"

Image depicting a star being pulled by a black hole's instense gravity

So what makes a black hole's gravity pulls so strong?

Being called a "hole" doesn't mean  it's an empty space. It in fact a huge volume of matter squeezed and packed into a very small radius. A perfect analogy taken from the NASA website says it will be like squeezing a star ten times more massive than the sun into a sphere approximately the size of New York City. The result would turn out to produce an extremely dense structure in space, one in which it mass will cause an infinite curvature in space-time and it gravity, so strong that no matter can escape it immerse pull.

When the statement "sucks any matter found near in vicinity" is often made anywhere when talking about black holes, that shouldn't make one try to visualize black holes as cosmic vacuum cleaners that swallow up any matter close to it.  Although it seems quite easier to try to view from this perspective, but the truth remains that, black holes doesn't actually swallow matters to itself (as would vacuum cleaners), their gravity just smear and pulls objects towards it center. These objects in turn, due to being acted upon by series of chaotic forces will be spewed out in some way. Thus, it will be more accurate to think of a giant tonadoe when thinking of a black hole, but this time with a drawing force caused by gravity, not by rotating wind.

The event horizon

The center(or the core) of a black hole is where the extreme gravitational pull takes place, and this region is associated with an event horizon. On a black hole, an event horizon is the boundary where the speed needed to escape a black hole's extreme gravitational pull will exceed the speed of light. That means that an object needs to travel faster than light to escape a black hole's event horizon.

But according to Einstein's special theory relativity, nothing can travel faster through space than the speed of light. This means a black hole's event horizon is essentially the point from which absolutely nothing can 

return. 

Formation of black holes

The idea behind the formation of black holes were first predicted by Einstein's field equations for the general theory of relativity. The prediction was that if an object is sufficiently massive or dense,(like a neutron star) there will become a point that it will collapse in upon itself and then become even more denser  that it creates an infinite distortion in space-time, resulting in an object with a very strong gravitational influence on nearby objects. The object having such property were later termed as a black hole.

In accordance to that, it was thus observed that when a neutron star(a very dense, heavy type of star) finally becomes too massive and its gravity becomes too much to handle, the star collapses on itself and explodes leaving behind a black hole. 

Black holes were never seen or observed by scientists with ordinary space telescopes that were used to detect light and other space radiations.  Even after years of studying, research, argument, etc. It continued to remain a hypothetical prediction.

 Astronomers and astrophysicists however we're only able to deduce the presence of a black hole on space by detecting it gravitational effect on nearby stars and objects. For example, when a star or other interstellar objects crosses a black hole, they will be teared apart and drawn inward  Not long after the invention of the event horizon telescope that astronomers were now able to  photograph the first image of a black hole.

Image showing the first actual photo of a black hole and it shadow, taken by the event horizon telescope at the center of galaxy M87.

Historical prediction of black holes

In 1915,  Einstein published his general theory of relativity in which he showed that gravity is not an attractive  force existing between two masses as Newton said, but gravity is a function of space-time curvature. He included series of equations along with his theories to justify his claims. These equations are popularly known as "Einstein's field equations"(EFE). These equations related how the geometry of space-time affected other parameters like mass, energy, momentum, and stress. In short terms, the equations summaries the relationship between matter and the geometry of space-time. Due to the non-linear nature of Einstein's equations, Einstein himself assume that they were unsolvable. Lots of effort were made by other mathematicians and physicists in solving the field equations and understanding it solutions.

Not long after, in January 1916 Karl Schwarzschild a German physicist and astronomer produced the first exact solution to the field equations. He used Einstein's field equations to calculate the outcome of the gravitational effect of a single spherical body, such as a star.

The first case was that : If a mass of a star is neither very large or highly concentrated(made to be very dense), the gravitational influence of the star on other nearby matter will just be the same as that given by Newton's theory of gravity. That is to say that the gravitational force of attraction of the star will be given by F=GMm/R². Thus, Newton's theory was not incorrect, rather it justifies general relativity under certain conditions.

For a weak gravitational field, the result of general relativity does not differ significantly from Newton laws of gravitation. But for intense gravitational field, (i.e one cause by a large or extremely dense mass generating instense curvature in space time) the result diverge, and general relativity has been proven to predict the correct result.

The second case was the most important one, as it predicted an extraordinary object in space. The second case was that : If a body of mass were concentrated or confined within a vanishingly small volume, the resulting calculation shows that there will come to occur a point of infinite curvature and density - a singularity- in at the center, where gravity will become so strong that nothing pulled into the surrounding region can ever leave. Even light cannot escape.

Yes, black holes were first predicted by Einstein's general law of relativity. But as technologies advanced, we were able to observe our first actual black hole back in 2016.  It was thus proving Einstein's prediction to be correct.  

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The 4 fundamental forces of nature

 A force by definition is a push or pull that an object exerts on another, causing it to experience motion or deformity. Everything in the universe experience some kind of force that react with it in every second. These forces can be grouped in four major fundamental units and termed as "the four fundamental forces of nature".

The four fundamental forces of nature are the most major forces that govern the behavior of everything in the universe and they cannot be further divided into any other basic forces. They can also be termed as the fundamental interactions. The are the simplest unit of force in which other forces present in the universe are built on.

These forces include:

• Gravitational force
• Electromagnetic force
• Weak nuclear force
• Strong nuclear force

These forces can be either short range or long range, depending on the number of bodies they act on. Each of these forces will be briefly explained in this post.

Gravity

In the elementary stage, gravity was defined as the force that tends to pull all object towards the center of the earth. But the earth is not the only system that has or experience the influence of gravity, in theory, everything in the universe having mass will experience gravity.

Gravity is thus a force that that attract two or more objects having mass together. Gravity surrounds us, it responsible for pulling all objects having mass towards earth's center example when you throw a ball  into the air, it returns to you because of the earth's gravity. The earth is surrounded by a gravitational field and this force of gravity on the ball is what pulls it back to the earth.

Gravity is also what binds planets in an orbit around the sun. Gravity by nature is too weak to be noticed unless at least one of the masses is very large. As described by Einstein's general law of relativity, gravity comes as a result of space-time curvature. If an objects has more mass, it will create more curve in space-time and consequently will have more gravity. That is exactly why the gravitational attraction between planet's orbital around the sun appears to be stronger because the sun has a relatively greater mass, creating more space-time curvature(as Einstein explained) and thus more attractive force.

Newton was the first scientist that discovered the force of gravity while watching a falling apple from a tree and asked why the apple fell. He later postulated his laws universal gravitational law, stating that the force of attraction between two bodies of mass m1 and m2 is inversely proportional to the square of their distance R between their centers and is directly proportional to the product of their mass.

This can be represented mathematically as:

F= Gm1m2/R^2

Where 

G= the universal gravitational constant

m1 & m2 = the masses of the two bodies

R = the distance between them

From this equation, we can calculate the gravitational force of the earth to be equals to 9.807m/s^2.

Overview of gravitational force

- It are the weakest among  the four fundamental forces, having an infinite strength of 1.

-It always tend to attract objects, it never repels them.

- It cannot be modified, absorbed or shielded against.

- It has an infinite range, thus it capable of holding planets, stars and galaxies

- It hypothetically uses gravitons as the mediators

- Mass acts as the main source. 

Electromagnetism

The word "electromagnetism" contains two terms, namely electricity and magnetism. It was long thought that electricity and magnetism  were separate forces, ideas changed as Einstein's law of relativity describes electricity and magnetism not as separated forces, but as inter-related phenomena. Electricity gives rise to magnetism and vise-versa. 

Electromagnetic force is a force that acts between electrically charged particles (electrons, protons, ions, photons) and it's so named as it exhibit  both the property of electricity and magnetism. 

It is the force that causes like charges to repel each other and unlike charges to attract each other. These phenomenon of attraction and repulsion is what binds electrons close to their orbitals, as they are attracted to the positively charged neutrons in the neucleus.

Light also is an electromagnetic wave, that undergoes continuous oscillation from electric field to magnetic field at right angle to each other.

Electromagnetic induction is also a phenomenon of electromagnetism, where electricity can be generated using  changing magnetic field across a coil of conductor.

So as we can see, electromagnetic force plays a vital role in our day to day living.

Overview of electromagnetic force

-  It is the force that acts upon charged particles, and it  contains both electrical and magnetic properties.

- It is the second strongest fundamental force of  nature, having an infinite strength of 10^36

- The also posses an infinite range.

- Photons acts as their mediator

- They travel at the speed of light(300 000 km/s)

Weak nuclear force

The weak nuclear force or weak interaction is the force responsible for nuclear changes in the sub-atomic particles, these changes includes; nuclear fusion (which is the combination of atomic nucei), nuclear fission(which is the disintegration of atomic nucleus), beta decay( process of converting neutrons to protons and vise-versa) , and electron capture. 

These nuclear changes are very vital for the working of the universe and even life on earth. For example, nuclear fusion is responsible for generating energy from the sun and other stars, where hydrogen is converted into helium.

Overview of the weak nuclear forces

- It is responsible for nuclear changes in sub-atomic particles

- It is the third strongest fundamental forces of nature having an infinite strength of 10^25

- They occur at a very short range as it only acts upon sub-atomic particles. Hence, it has a infinite range of 10^-18

- W and Z bosons acts as the mediator

Strong nuclear force

The strong nuclear force is by far the most strongest and complex force in the universe. It only act upon sub-atomic particles in the nucleus. The atomic nucleus is made up of protons and neutrons, the protons possesses a positive charge while the neutrons are electrically neutral. The protons which were supposed to repel each other because of their like charges are tightly binded together in the nucleus by the action of a force called the strong nuclear force.

The electromagnetic force couldn't possibly keep the nucleus of an atom together, because it is much too weak, and the protons would simply repel one another and fly, because they are all positively charged, and we know that two positively charged particles won't attract each other. So there needs to be a stronger force, and that just happens to be the Strong Force. This force is also responsible for binding Quarks and Gluons into Protons and Neutrons.

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What is superconductivity

Superconductivity is a phenomenon that explains the ability of some materials to conduct electricity with ideally zero resistance, zero energy loss, and zero magnetic fields, when cooled to critically low temperatures. This fundamental property of some materials was discovered by a Dutch scientist named Heike Kamerlingh Onnes in 1911, when he succeeded in cooling Mercury to 4.19 degrees Kelvin and discovered that the instrument suddenly measured zero resistivity. 

Purpose of superconductivity

One of the major problems facing a non-ideal system is "energy losses". It can come in form of heat, sound, or even as a light wave. No matter how it transmitted, it definitely an unacceptable and unavailable situation. Particularly in the field of electricity, non-ideal conductors 

Scientists however has been making deep advancement into developing an ideal or close to an ideal conductor with zero energy loss. 

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Concepts of electromagnetic force

 

The word electromagnetic force consists of two qualitative distinct forces: electricity and magnetism. It is the force acting on either or both an electric charge or on a magnetic pole. It is called "electromagnetic" since the "electric" or "magnetic" nature of the force depends on how the object which is feeling that force is moving relative to the source-charges that are causing this force. For example, an electric charge moving in a magnetic field, i.e. near magnets, is experiencing an electric field, meaning it feels as if it were at rest near electric charges. It is customary to say that the "electric" or "magnetic" nature of the field o is a relative nature of the motion thus it is best to call this force "electromagnetic".

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Introduction to Thermodynamics

 

Thermodynamics is that branch of science ,which deals with conversion of heat energy into other form of energies and describe their conversions quantitatively. Initially ,thermodynamics was means to deal with conversions from heat energy into mechanical work and vice versa. since we know that different manifestations of energy are inter convertible, according to the law of conservation of energy, the scope of thermodynamics have been enlarged to cover conversion of heat energy to other forms mechanical, electrical, magnetic , chemical etc. The thermodynamics deals with innumerable phenomena covering the different branches of physics ,chemistry and engineering.

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Semiconductors - theory and applications

The study of electricity has since been limited to the nature of current on conductors and insulators until when researchers decided to explore more on semiconductors. Materials whose conductivity falls between those of conductors and insulators are called semiconductors. Semiconductors are “part-time” conductors whose conductivity can be controlled.

Silicon is the most common material used to build semiconductor devices. Si is the main ingredient of sand and it is estimated that a cubic mile of seawater contains 15,000 tons of Si. Si is spun and grown into a crystalline structure and cut into wafers to make electronic devices.

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How do solar panels works?

The annual increasing rates of global warming and carbon emission has opened up a the revolution of a cleaner energy. Thanks to advanced research on the theory and concepts of semiconductors, we can now efficiently utilize energy from our earth's longtime neighbor the sun. It was proven that the amount of energy released by the sun in just a second, is capable of powering the whole of the united states for about 9 million years.

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How radio frequency works

 

Radio waves are electromagnetic waves that include light, microwaves, x-rays, infrared, ultraviolet, etc. Radio waves are composed of both electric fields and magnetic fields. In fact, a wave is produced when a time-changing electric field induces a time-changing magnetic field and then the time-changing magnetic field induces another time-changing electric field and the process repeats. This is all described by a set of equations modified and assembled by James Clerk Maxwell, so today they are called Maxwell’s equations.

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Understanding the band theory

 

The band theory is basically an extension of the molecular orbital theory which satisfactorily explains the electrical properties of solids.The molecular orbital theory postulates that when two atomic orbitals of similar energy of two different atoms combines or overlaps with each other they loose their identity and form new orbitals 

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Understanding magnetic field, magnetic flux, and magnetic flux density

 Analogies are often effective in explaining matters relating to physics most especially when two or more terms sounds quite similar and complicated. In our previous post, we were able to explain speed, velocity, and acceleration using analogies and in today's post, we have yet another group of physics philosophy which sounds quite similar and complicated to understand. So we'll try and break it down by applying it rules to a more common objects. Let start by their definitions.

Magnetic field

A magnetic field is a region around a magnet or a current-carrying conductor, where a magnetic force is experienced or where a magnetic force exist. The direction of this magnetic field is represented by magnetic field lines.

Magnetic flux

The magnetic flux  is therefore proportional to the number of magnetic field lines passing through a magnetic field. For simplicity sake, just view the magnetic field lines as just the individual lines, then view the magnetic flux as the whole lines put together. The magnetic flux determines the strength of a magnetic field, i.e the more the magnetic flux set up, the stronger the magnetic field. Therefore, the magnetic flux is the net number or quantity of the magnetic field lines set up or produced in a magnetic field.

Magnetic flux density

This is defined as the magnet flux per unit area in a given magnetic field. While the magnetic flux determines the total strength of a magnetic field, the magnetic flux density determines the strength of a magnetic field just IN A GIVEN AREA. 

Now let move to the analogies.

Magnetic field: Let use a standing fan as an example. When you switch on the fan, it will blow the air around itself and you will feel the air. When you move closer to the fan you will feel the air pressure more intense. When you move farther away from the fan you will feel the air pressure lesser and as you continue to move away, the air pressure diminishes. Now let take the region that you experienced the air as fan field. If we are to define the fan field, we would say that the fan field is a region that a fan force(which is air) is experienced. Comparing it to the magnetic field, the magnetic field is just a region that a magnetic forced is experienced. But we humans cannot experienced a magnetic force but metals do.

Magnetic field lines: The standing fan is pushing the air towards a specific direction. But can we see it. No. But we can thus feel it. In fact if we were to draw lines representing the direction of the air, all we have to do is we will just try to visualize where we're recieving the breezes from and then draw an imaginary line showing the direction of the air. That is what magnetic field lines is all about. Magnetic flied lines(or magnetic lines of force) is just an imaginery line that shows the direction in which a magnetic force is comming from.

Magnetic flux:  A magnetic flux is represented to be the whole magnetic lines of force put together. Let consider a moment when the fan blades rotate at high speed, we will notice that even if we move farther away from the fan and in a slightly different direction, we will still feel the air intensely and the number of our imaginary lines will appear to be much because we will be receiving the air from all directions. So likewise, when the magnetic field is stronger, it will generate more magnetic field lines which will increase the magnetic flux. 

Magnetic flux density: To understand magnetic field density, let take a different approach. Let use the aspect of population density. The population density of a country is just a net number of people living in a particular country(maybe china). So the magnetic flux density is the amount of magnetic flux present in a given area. NOTE; "a given area" in a magnetic field not the whole magnetic field area. Just as the population density of a country can be greater or less than the one in another country. Likewise, the magnetic flux density in a given area can be greater than the one in another area. Consider when you stand by the side of the fan,, and when you stand in front of and when you stand at the back of the fan. You won't receive the same intensity of air, because the air density  varies from region to region.

 

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Understanding Active, Reactive, and Apparent power in an AC circuit

 When dealing with power in an AC circuit, you'll definitely come across these terms; Real(or active) power, Reactive power, and Apparent power. What is their difference? 

This post will explain all you need to know about power in an AC circuit, bit by bit.

What is electric power: Electric power refers to the rate in which electrical energy is transfered in an electric circuit. It is the rate per unit time at which work is done in a circuit.

In a linear AC circuit(circiuits that obeys ohms law hence, V=IR), we have basically two types of loads, which are:

1. Resistive loads: These are loads that just consume electrical power and dissipate them in form of heat while performing useful functions. For this kinds of load, current remains in phase with voltage i.e they draw current in the same proportion as the applied voltage. The type of power consumed by them is called the active power.

Examples of resistive loads include: Resistors, Electric heaters, incandescent bulbs etc.  

2. Reactive loads: These are loads that store power temporariy in the circuit and unlike resistive loads, energy consumed by reactive loads are not dissipated as heat but rather it is stored  for some time and again returned back to the circuit, making the net energy consumed by it to be zero. In reactive loads, There are two types of reactive loads.

* Capacitive loads and

* Inductive loads.

Examples of reactive loads include:  Inductors, transformers, line capacitors etc. The kind of power used by reactive loads are called reactive power. 

Note that reactive loads ideally do not consume power. But in practice, all reactive loads has some resistive component and leakages present, which causes power to be dissipated as heat and resulting in energy losses.

What is Active power

This is the actual amount of power that is being expended in the circuit to perform useful work  e.g creating heat, lighting a bulb etc. It is the power that is actually being dissipated by the circuit due to it resistive component. In other words, when your're using your household equipment, like Lightbulbs, Electric irons, TVs,  Washing machines etc power is being expended and the amount is reading on your meter. This kind of power which is being consumed by the circuit to do useful work is called active power. 

Active power can be alternatively called real, actual, useful or true power and it measured in Watt or kilowatt.

Formulas for calculating active power:

P = V I (In DC circuits)

P = VI Cosθ (in Single phase AC Circuits)

P = √3 VL IL Cosθ or (in Three Phase AC Circuits)

P = 3 VPh IPh Cosθ 

P = √ (S2 – Q2)or

P =√ (VA2 – VAR2) or 

Real or True power = √ (Apparent Power2– Reactive Power2) or

kW = √ (kVA2 – kVAR2)

What is Reactive power

The power that is not utilized to do any useful work but it continuously transfered from the load to source is called reactive power. 

In an AC circuit, Not all loads do consume power or dissipate them as heat. Taking a capacitor and an inductor for example. Inductors and capacitors ideally do not dissipate electric power but rather stores them in form of magnetic field and electrostatic field respectively. Power is needed to establish this respective fields. So the power needed for a capacitive load to build up an electrostatic field or for an inductive load to build up a magnetic field is called reactive power. It is called reactive power because the power consumed is not dissipated as heat or utilize to do any useful work. These fields will only build up in the positive half cycle of the AC waveform and will be given back to the circuit in the negative half cycle, making the net power consume by it to be zero.

Reactive power is measured in volt ampere reactive(VAR)

Formulas for calculating reactive power:

Q = V I Sinθ

Reactive Power=√ (Apparent Power2– True power2)

VAR =√ (VA2 – P2)

kVAR = √ (kVA2 – kW2)

If Active power is called useful power, does it mean that reactive power is useless?

No, not at all. Let use a ceiling fan as an example. Without the AC capacitor present inside the fan, the fan blades won't rotate. But power is thus needed to charge this capacitors and this power does not contribute in rotating the fan, but without the capacitor being charged, the coils making up the fan won't be energized and the fan won't rotate. So the energy used to charge the capacitor is not utilize to do any useful work as it just charging the capacitor. When the capacitor is fully charged, it will thus deliver this energy to the fan colis which will then utilize it to perform the useful work which is rotating the fan blade. 

What is Apparent power

Apparent power is the mathematical combination of active power and reactive power. It equals to the total power in an AC circuit, both dissipated and absorbed/returned. Thus in apparent power, the phase angle difference between the voltage nd the current is ignored.

Formulas for calculating Apparent power:

S = V I

Apparent Power = √ (True power2 + Reactive Power2)

kVA = √kW2 + kVAR2.

If you need further reasonning, you can consider the wheel barrow analogy below;

In order to make the wheel barrow move, it is obvious that we’ve to apply force at the handle.

But the force should be applied in the forward direction only after lifting the handle. Otherwise there would a hindrance for the motion due to the leg of the wheel-barrow.

Active Power is that which results in active work (propelling the wheel-barrow in forward direction). So active power is solely that work which is done on the wheels of the barrow for the procurement of real (useful) work. 

Reactive Power can be reckoned as that which helps to keep the barrow in the lifted position.

The total power which is the Apparent Power (Lifting + Pushing) is that which is applied at the handles.

Just imagine what would happen if the wheel barrow is thrust forward without lifting? The barrow moves forward, but not with much ease. There is much difficulty encountered to the person who is pushing it as well as on the wheel barrow. The same applies in the case of transmission system also. If reactive power support is not provided then there is much difficulty in transfer of power between buses. Moreover, in the case of a wheel barrow, one has to incur extra work in lifting the barrow so that it moves forward smoothly. Thus, reactive power is a necessary evil (it is not a part and parcel of useful work but it helps in useful work being done more easily).

Analogy extracted from quora.com

Hope you enjoyed the post. If you have any question concerning this post or other post, kindly includeit in the comment box below, I'll be glad to respond. And don't forget to subscribe for more interesting post like this one.

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Understanding speed, velocity, and acceleration by analogies

The concept of speed, velocity and acceleration is what we are experiencing in our daily life. From rolling a ball, to riding a bike, to boarding a train, we are all experiencing the effect of speed, velocity, and acceleration, so it not just a mathematically proven fact, like the special theory of relativity.

When basic physics parameters like this is explained by analogies, it helps students to get a clearer picture of what is really happening and how it affect us. In this post, we will explore series of analogies that will help us understand some of these elementary parameters of physics.

But first, there are two more things we have to understand. There are the two types of physical quantities - SCALAR and VECTOR

SCALAR - when just the magnitude is enough (i.e the size or just the number).

For example, my height is 80cm, the temperature is 30degrees, distance between California and Texas is 500km.

VECTOR - When direction and magnitude are both required for understanding. For example, the velocity of the car I saw was 30km/hr toward North, I applied 40N force on the bench downwards.

Now we've understand what scalar and vector are, let proceed to our main business. 

Speed: Speed is defined as the rate of change of distance moved with time. Speed, as a scalar quantity has a property of magnitude(size) but no direction. For example an object moving at a speed of 40ms^-1  has an higher speed than one moving at a speed of 20ms^-1 .

Velocity: Velocity is defined as the rate of change of distance moved with time(or the rate of change of displacement with respect to time) in a specified direction. The term velocity is not the same as speed. It has both magnitude and direction. Hence it is a vector quantity.

Acceleration: Acceleration is defined as the rate of change of velocity with respect to time.  Acceleration is the second derivative of displacement.

Speed and velocity are pretty much the same thing, with just one difference. Direction. If you assign a direction to speed, it becomes velocity. So now we know the theoretical definition of speed, velocity and acceleration. Let now move to the practical definition of it.

Speed: Speed is simply how fast an object is moving. Let use a roller coaster analogy. As we all know that a roller coaster moves in a circular and directionless manner. So it has just speed but no velocity. So we can say that the rollar coaster moves at the speed of 12m/s or the speed increases to 30m/s. That's just it, no direction is needed to understand.

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Velocity: Velocity has to do with how fast an object is moving towards a given direction. For example if your boarding a train towards the East, the speed of the train could be just 300km/hr, but if you were to specify the direction, you will say that the velocity of the train is 300km/hr towards North. Now there is direction. 

Sometimes speed and velocity are often used interchangeably, you might often hear that a car was moving at a velocity of 20m/s or so. It all the same, but when asked for velocity, always try to include the direction.

Acceleration: Acceleration refers to how fast an object switches it speed in a time duration. Consider a car at rest, when you start the engine and hold the accelerator peddal, even if you put it at the highest speed you will still notice that it will take time before the car will start moving at it highest speed, it will start slowly untill it begins to move faster. 

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Why do birds and squirrels not get shocked by the high voltage power lines

Do you sometimes wonder why birds and some other animals like squirrels, sit and play over high voltage transmission lines without getting electrocuted? Our curiosity can go as far as making us assume that birds and squirrels feets are covered by strong insulators, or their body are resistance to electricity. The fact is that none of these assumptions are basically true because the reason why this happens is not owing to any special abilities. Birds or squirrels are absolutely not immune to electric shock( as you see in the image below). Here is what really happens.

photo of a dead bird hanging on a transmission pole

What is electric shock or electrocution: Electric shock is the sudden discharge of electric current into the body which can cause severe injury or a permanent damage to the body. Electrocution is when the victim dies from it at that point. For us to know why current isn't flowing through birds or squirrels sitting on a high voltage wires, we first have to know the three things needed for electric current to flow in the first place.

What is needed for current to flow 

For electric current to flow continuously, there must be: 

• A voltage source: Voltage is what provides the electromotive force for electrons to flow round a circuit. Just like a water pump is needed to provide the pressure needed to pump water through a pipe, so in the case of electricity, voltage is what provides the drive force for electric current and it always  relative  between two point. You'll never see a battery or an AC generator having just one terminal, it should have two active wires or terminals.

• A closed circuit: For electrons to flow continuously, they must be a  path, and that path is called a circuit. But electrons doesn't have infinite sources and destinations so a closed circuits provides a complete path for electrons to flow round a conductor. It doesn't matter the type of current, whether it an alternating current(AC) or a direct current(DC) they all require a closed circuit.

• A path of NO or relatively LOW resistance: There is practically no conductor with zero resistance, but for electric current to flow the resistance on a circuit must not be high enough to completely stop the flow of current in that circuit. Electric current highly prefer the path of lower resistance, that means a very least amount of current will flow in a in a path filled with electrical resistance.

Each of these 3 criteria plays a role on why birds and squirrels do not get electrocuted when playing on what suppose to roast them to ashes. Let explore.      

POINT 1:   ONE POINT CONTACT - As we’ve already learned, electricity requires a complete path (closed circuit) to continuously flow. Without two contact points on the body for electric current to enter and exit respectively, there is no hazard of shock. This is why birds and squirrels can safely rest on high-voltage power lines without getting shocked because they make contact with the circuit at only one point. When current is generated from the source (power plants) to the transmission lines, it follows a loop pattern. From the  live wires to different loads (transformers, home appliances) and then the earth wire(or ground) acts as the return path for this current to flow back to the source . Birds or squirrels do not take part in this loop because they always land on either of these wires. 

POINT 2: In order for electrons to flow through a conductor, there must be a voltage present to motivate them. Voltage, as you should recall, is always relative between two points. There is no such thing as voltage ”on” or ”at” a single point in the circuit, and so the bird contacting a single point in the above circuit has no voltage applied across its body to establish a current through it. Yes, even though they rest on two feet, both feet are touching the same wire, making them electrically common. Electrically speaking, both of the bird’s feet touch the same point, hence there is no voltage between them to motivate current through the bird’s body.

For schematic view of both scenario, see this diagram:

As we can see that the safe bird, appears to be electrically common.

POINT 3: Birds,  squirrels and even some other animals have a rather higher resistance to electricity. As earlier mentioned, electric current flow chooses the path of lower resistance. Birds do not offer an easy path for current to flow due to it high electrical resistance, so current bypasses the birds and chooses the path of lower resistance which are the copper or aluminium cables.

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What causes lightening and thunder and why do we see lightening before hearing thunder

Do you sometimes wonder why we often see lightening flashes first before we hear the sound of thunder? What is the science behind it and how can you protect yourself from being struck by lightening? Find out these answers and more below.

Lightening flashes and associated thunder does occur when our atmosphere attains instability. This means that the factors surrounding our atmosphere will swift from the normal level and either increases or decreases rapidly. During thunderstorms, the atmosphere becomes unstable due to the increase in air pressure, humidity, charge particles, cloud imbalances etc, this will thus trigger the actions of lightening sparks and  thunder strikes.

The science behind lightening

Lightening is  a very powerful electrical discharge in our atmosphere caused when the imbalance of charge particles between clouds and other regions tries to equalize themselves generating millions of voltage capable to breakthrough the resistance of air. The action will then produce a visible spark reaching over five miles (eight kilometers) in length and raising the temperature of air up to 60, 000 degrees Fahrenheit(33, 400 degrees Celsius), that's 6 times  hotter than the surface of the sun.

The phenomenon of lightening is really due to the concept of static electricity where unlike charges tend to attract each other and like charges repel.When the atmosphere and clouds becomes saturated with moisture, the particles of rain, ice, or snow inside the clouds begin colliding and bumping into each other, this collision will then cause a static electricity between them and often positive charge particles  will move to the top of the cloud  while negatively particles will settle in the bottom of the cloud.

Charge formation in the clouds(image by britannica.com)

             This charge indifference will accumulate up to a point that they start demonstrating an attractive force between each other, since there is no conductive path for current to flow, the voltage(or charge indifference) will accumulate until it supersedes the resistance of air and electric current is then forced to conduct through air and thus creates an electric arc or what we call lightening. Objects on the ground, like trees, skyscrapers, power towers, telephone mass, and the Earth itself, becomes positively charged and will also attract the negatively charge particles from either the cloud or air and join in the game.

What causes the sound of thunder

Thunder is not a phenomenon of it own, but it caused by lightening. When lightening occurs, it will generate an enormous amount of heat into the air, one hotter than the surface of the sun. This will cause the air in the lightening channel to compress to a huge amount increasing it normal atmospheric pressure up to 10-100 times. As the air now then tries to expand from compression into it normal state, it does so at a supersonic speed, forcing itself out of the channel, which ultimately produces a loud sound, heard as thunder. Just like when you inflate a balloon, you're in fact increasing the air pressure inside balloon, and when you pop it, air is force out of the balloon, producing sound. Thunder just does so in a large scale.

So we can see from our explanation that since lightening causes thunder, it just a situation of normality for us to see lightening first before thunder. I personally don't accept with some common assumptions that we do see lightening before thunder due to the fact that light travels faster than sound. It is thus true that the speed of light is greater than sound, but putting matters into perspective we can see that this has absolutely nothing to do with speed here or how light travels, it's just not possible for the thunder, which is caused by lightning, to be heard first before the lightning.

One more myth about thunder is the fact that thunder is completely harmless because it just a sound. This is also practically not so true. While the action of thunder involves the production of loud sounds, thunder is not just about the sound produced. The sound of thunder if it loud enough and at a close range, can damage the ears and may cause temporary deafness.

Most importantly, thunder is produced by a sudden expansion of air from a lightening bolt. The air is thus released at a supersonic speed raising it pressure up to 100 times more than normal. If produce at a very close proximity, the extreme shock wave cause by it is capable of blowing a human off the ground, causing property damage etc. Windows and glass materials have been the most vulnerable substances during the action of thunder in my area. And lastly, the internal shock and fear you perceive during a sudden and an unexpected thunder strike can lead you to astray to running directionless into a dangerous object.

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Why is it said that electrons are negatively charged

 The separation of electric charges into positive and negative still sounds much of a brain box to some curious new physicist, especially in the field of electrical and electronics engineering. But the interesting fact about this is that it was all because of Benjamin franklin's arbitrary decision.

Are you actually a curious type? Do you want to know they full fact behind the ideas that :

1. Electrons possesses a negative charge, while protons are positively charged.
2. Like charges repel while unlike charges attract

This post will explain all of the in depth concept of electric charges using the theory of static electricity. 

Why do knowing these facts matter:   Real scientists and inventors who make a difference don't only limit themselves with implicit explanations, but they move further to know more on the underlying concept of scientific theories. Of cause there is no big deal about just seeing things as everyone does, but to be an inventor, you'll have to be curious enough to fully grasp the root cause of how things actually works, not just how to make things.

What are charges anyway 

To understand the concept of electric charges, let first revisit the past a bit.

          It was discovered centuries ago that certain types of materials would mysteriously attract one another after being rubbed together. For example: after rubbing a piece of silk against a piece of glass rod, the silk and glass would tend to stick together. Also, when a paraffin wax is rubbed with wool cloth; they are seen to attract each other. Indeed, there was an attractive force that could be demonstrated even when the two materials were apart.

This phenomenon became even more interesting when it was discovered that identical materials, after having been rubbed with their respective cloths, always repelled each other. For example: lets consider two glass rods rubbed with silk and brought together. They are seen to repel each other:

Even the materials used to do the rubbing will also tend to repel each other. For example: Two wool cloths will be seen to repel each other after they were used to rub different paraffin wax. Same goes for two silk cloths used to rub different glass rods.

What could have caused this invisible force of attraction and repulsion?  Whatever change that took place to make these materials attract or repel one another was invisible.

         Some experimenters speculated that invisible ”fluids” were being transferred from one of the material to another during the process of rubbing, and that these ”fluids” were able to effect a physical force over a distance. Charles Dufay was one of the early experimenters who demonstrated that definitely two different  types of changes  took place by rubbing certain pairs of objects together.  This idea that there was more than one type of change manifested in these materials was due to the fact that  two types of forces were produced: attraction and repulsion. The hypothetical fluid transfer became known as a CHARGE.

         

What is the concept of positive and negative charges

 One pioneering researcher, Benjamin Franklin, came to the conclusion that there was only one fluid exchanged between rubbed objects, and that the two different ”charges” were nothing more than either an excess or a deficiency of that one fluid. After experimenting with wax and wool, Franklin suggested that the coarse wool removed some of this invisible fluid from the smooth wax, causing an excess of fluid on the wool and a deficiency of fluid on the wax. The resulting disparity in fluid content between the wool and wax would then cause an attractive force, as the fluid tried to regain its former balance between the two materials. 

           His postulations reveal that during the rubbing process, the two materials concern must fall into either of the two opposing categories. In other words, one must be in excess while the other must be in deficiency. There was never a time where two materials rubbed against each other both became either in excess or in deficiency. 

          Following Franklin’s speculation of the wool rubbing something off of the wax, the type of charge that was associated with rubbed wax became known as ”NEGATIVE” (because it was supposed to have a deficiency of fluid) while the type of charge associated with the rubbing wool became known as ”POSITIVE” (because it was supposed to have an excess of fluid). Little did he know that his innocent conjecture would cause much confusion for students of electricity in the future!

 

 NOTE: The idea of using negative and positive as the word was simply an arbitrary decision by franklin. Since the word "negative" always refers to lack of something and positive designated to a possession of...  

Why is the word "negative" designated to Electrons and "positive" to protons

        It was discovered much later that this ”fluid” was actually composed of extremely small bits of matter called  ”ELECTRONS ”, so named in honor of the ancient Greek word for amber: another material exhibiting charged properties when rubbed with cloth. Experimentation has since revealed that all objects are composed of extremely small ”building-blocks” known as ATOMS, and that these atoms are in turn composed of smaller components known as particles. The three fundamental particles comprising most atoms are called protons, neutrons and electrons. 

However, electrons have significantly more freedom to move around in an atom than either protons or neutrons. In fact, they can be knocked out of their respective positions (even leaving the atom entirely!). If this happens,  an important imbalance will  occur. Electrons and protons are unique in the fact that they are attracted to one another over a distance. It is this attraction over distance which causes the attraction between rubbed objects, where electrons are moved away from their original atoms to reside around atoms of another object.

            Electrons tend to repel other electrons over a distance, as do protons with other protons. The only reason protons bind together in the nucleus of an atom is because of a much stronger force called the strong nuclear force which has effect only under very short distances. Because of this attraction/repulsion behavior between individual particles, electrons and protons are said to have opposite electric charges. That is, each electron has a negative charge, and each proton a positive charge.

The process of electrons arriving or leaving is exactly what happens when certain combinations of materials are rubbed together: electrons from the atoms of one material are forced by the rubbing to leave their respective atoms and transfer over to the atoms of the other material. In other words, electrons comprise the ”fluid” hypothesized by Benjamin Franklin. The result of an imbalance of this ”fluid” (electrons) between objects is called static electricity. It is called ”static” because the displaced electrons tend to remain stationary after being moved from one insulating material to another. In the case of wax and wool, it was determined through further experimentation that electrons in the wool actually transferred to the atoms in the wax, which is exactly opposite of Franklin’s conjecture! In honor of Franklin’s designation of the wax’s charge being ”negative” and the wool’s charge being ”positive,” electrons are said to have a ”negative” charging influence. Thus, an object whose atoms have received a surplus of electrons is said to be negatively charged, while an object whose atoms are lacking electrons is said to be positively charged, as confusing as these designations may seem. By the time the true nature of electric ”fluid” was discovered, Franklin’s nomenclature of electric charge was too well established to be easily changed, and so it remains to this day.

Why do like charges repel and unlike charges attract

If we take the examples of wax and wool which have been rubbed together, we find that the surplus of electrons in the wax (negative charge) and the deficit of electrons in the wool (positive charge) creates an imbalance of charge between them. This imbalance manifests itself as an attractive force between the two objects:

The imbalance of electrons between the atoms in the wax and the atoms in the wool creates a force between the two materials. With no path for electrons to flow from the wax to the wool, all this force can do is attract the two objects together

Dedicated to the book "Lessons In Electric Circuits, Volume I – DC"

 By Tony R. Kuphaldt

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What is conventional current and why is it opposite to electron flow

Many students of physics and electrical engineering are confused by the idea of conventional current. If current is due to the flow of electrons, and direction of flow of electrons is from negative to positive, then what's with this conventional current of a thing, and why is it opposite to electron flow. 

To understand this post fully, I would recommend you first read about the concept of charged particles  in my previous post on why is it said that electrons are negatively charged. It will give you the ground basis on why it was necessary to introduce conventional current notation. 

This post will explain all you need to know about conventional current and why it opposite to electron flow. But first, let make sure we're on the same page by defining what electric current is.

What is electric current

When defining electric current due to current flow in metallic conductors, we would say that electric current is the flow of electrons. But the story sounds different when we consider the particles actually moving in electrolytes, (for e.g when a voltage source is applied to a glass of salt water,  what will happen is that positively charged sodium ions will move toward the negative terminal while negatively charged chloride ions move toward the positive terminal). This tells us one thing, that charged particles, which could be electrons, protons, ions, holes or both electrons and ions is what constitute current flow. 

      Electric current is thus the measure of flow of electric charge (or charges) through a conductor. But what direction do the charges actually flow to in terms of origin and destination?

What is the direction of electric current

 Benjamin Franklin in his experiment with static electricity, discovered that when a wax and a wool tend to attract themselves after they were rubbed together, it entails that bunch of invisible fluids (later discovered to be electrons) were trying to regain it former balance after they were displaced by the action of that rubbing. This invisible fluids will always flow from the region of excess(denoted to be positive) to the region of deficit(denoted to be negative). Expanding further with the wax and wool experiment, when wax and wool were vigorously rubbed together, invisible fluids will forcefully be displaced from one of the material to another. But from which material to which material?  Franklin then suggested that the coarse wool removed some of this invisible fluids from the smooth wax during the process of rubbing, causing an excess of fluid on the wool and a deficiency of fluid on the wax. The resulting disparity in fluid content between the wool and wax would then cause an attractive force, as the fluid tried to regain its former balance between the two materials.

Advancement in scientific research further made it clear that these ”fluid” was actually composed of extremely small bits of matter called electrons, and that they were actually displaced from the wool to the wax not from the wax to the wool as Franklin suggested. So the wax was the actual region of excess (or positive region) and the wool was the actual region of deficit(or negative). In other words, Franklin's suggested region of excess (which was the wool) was clarified to be the region of deficit and his suggested region of deficit(which was the wax) was clarified to be the real region of excess. So Franklin's conjecture of direction of charged particles was the other way round. What a confusion.

Why was a convention needed?

First of all, what is a science convention? A science convention is an international conference, that holds to set up a precise and generally acceptable standards in science parameters and unit of measurement.

By the time the true direction of electron flow was discovered, the nomenclature of ”positive” and ”negative” had already been so well established in the scientific community that no effort was made to change it, although calling electrons ”positive” would make more sense in referring to ”excess” charge. You see, the terms ”positive” and ”negative” are human inventions, and as such have no absolute meaning beyond our own conventions of language and scientific description. Franklin could have just as easily referred to a surplus of charge as ”black” and a deficiency as ”white,” in which case scientists would speak of electrons having a ”white” charge (assuming the same incorrect conjecture of charge position between wax and wool). However, because we tend to associate the word ”positive” with ”surplus” and ”negative” with ”deficiency,” the standard label for electron charge does seem backward. Because of this, many engineers decided to retain the old concept of electricity with ”positive” referring to a surplus of charge, and label charge flow (current) accordingly. This became known as conventional flow notation.

Hope you liked this post and also understands the reason why what they call conventional current exist and why they say it opposite to electron flow. If you have any doubt or question concerning this article, just include it in the comment box below and don't forget to subscribe if you want to be receiving notifications for interesting post like this one.

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