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PAPER BATTERIS

Paper batteries = Paper + Carbon nano tubes(CNT)

What are carbon nano tubes (CNT)?

Carbon nanotube is an allotrope of carbon. Allotropy is nothing but different structural modifications of an element. For example the following image shows the different alotropes of carbon

a-Diamond b-Graphite c-Lonsdaleite d-Buckminsterfullerene e-C540 f-C70 g-Amorphous

h-carbon nano tube

As you can see from the figure all the allotropes have different arrangement of atoms. For example, in case of diamond, the hardest element found on the earth, every single carbon atom is linked or bonded (covalent bond) with every other 4 atoms of carbon. Likewise, carbon nano tubes are a one of the allotropes of carbon where every carbon atom is linked with every other three carbon atoms and also form a cylindrical structure. Carbon nano tubes are man made. The graphite and diamond are alone the naturally occurring allotropes of carbon. 

What are paper batteries?

A paper battery is a flexible, ultra thin energy storage device made of cellulose (paper) and Carbon nano tubes. A paper battery can act as a super capacitor and also as a high - energy battery.

Working of paper batteries

Cathode : Carbon nano tube (CNT)

Anode : Lithium

Electrolyte : Bio electrolyte - blood, sweat, urine, etc

Separator : Paper

Source : BBC News © [2013]

Anode and cathode are the metal electrodes in the battery. The electrodes are placed in the battery in such a way that, they are in contact with the electrolyte. When an external load connected to the battery circuit is closed, current begins to flow because of the electro chemical reactions occurring inside the battery. Oxidation and reduction are the two main electro chemical reactions happening in any batteries. Oxidation takes place at anode and reduction takes place at cathode. Anode loses electrons to the ions from the electrolyte to form a compound and hence is said to be positively charged. Cathode gains electron from the electrolyte to form a compound and hence is negatively charged.

What is the role of the seperator?

The separator separates the anode and cathode. The batteries have to be very compact in size for the ease of use and hence the cathode and anode are closely packed. The separator acts as a barrier preventing the anode and cathode from touching each other. When they come in contact there will be no flow of current in external circuit.

Construction of paper batteries

1. A common xerox paper of desired length is taken
2. A specially formulated ink (with CNT) is spread over the paper
3. On the other side a thin film of lithium is laminated.
4. Aluminium rods are connected for carrying current.

Advantages of paper batteries

• Biodegradable & Non Toxic
• Reusable & Recyclable
• Durable
• Rechargeable
• No Leakage & Overheating
• Very Light Weight & Flexible

Applications

• Low battery power devices like in calculators, wrist watch and other low drain devices
• Laptop batteries, mobile phones, handheld digital cameras
• Wireless communication devices like mouses, keyboard, bluetooth headphones,etc

ROLLER COASTER

Roller coaster is an amusement ride! NO! It’s a heart pounding and a thrilling ride that makes you feel like you are going to fly right out of your seat. How does this scream machine work?

WORKING OF ROLLER COASTER

The roller coaster runs at a speed of 100km/hr. You may not believe, but the machine running at such great machine doesn’t have an engine. It’s like the winter sport, SLEDDING, where the car carrying 2 people is chained to dogs. The dogs carry the sled (the seated car) to the top of the hill. At the top of the hill the dogs are released and the car descends down the hill. The working of the roller coaster is very similar to sledding. But in roller coaster the action is repetitious.

There are two working technologies in roller coaster

Method A. Chain lift
Method B. Catapult lift

COMPONENTS OF ROLLER COASTER

1. The cars carrying the seating arrangement
2. Brakes
3. Driving components.

• In chain lift mechanism, pulleys and induction motors
• In catapult launch lift, electromagnets

Method A. Chain lift

Chain lift mechanism has a sinusoidal track. The car is pulled to the top by a pulley arrangement. The car then moves freely, like a free falling object under gravity.  The pulley is driven by an induction motor.  Assume the following image shows the track of the roller coaster

Track

Once the car reaches the top of the sinusoidal track (B), it is full of potential energy and falls freely to reach the bottom of the sinusoidal track (D), as its potential energy is being converted into kinetic energy.  Now at D it is full of kinetic energy. Its kinetic energy and it’s the wheeling action helps the car move to F. This goes on till a flat track is reached. 

Method B. Catapult lift

This mechanism works in a different way. Instead of being pulled up the hill, unlike chain lift, large amount of energy is built in a short period of time. It is done by placing one electromagnet at the first car and the other at the top of the track.

BRAKES

As roller coaster don’t use any motors, and rely on natural forces, it is essential to use brakes to stop the machine. This is done by the fins built underneath the track. These fins have a clamp like arrangement placed at the end of the track and at various other points of the track.  These fins hit against the bottom of the car and the car stops due to friction.

There are two types of roller coaster

1. Wooden roller coaster
2. Steel roller coaster

THE PHYSICS BEHIND ROLLER COASTER

The roller coaster is mainly driven mainly as its potential energy is converted into kinetic energy at every fall. The sinking feeling that you like or hate the most is mainly because of the forces acting on you. The first force acting is the gravitational pull and another force is the force of acceleration, the force due to the speed. At every point on the roller coaster, the earth’s gravitational pull tries to bring you down to the surface. The force of acceleration is pulling you against the gravity. When you are climbing on the track these forces are in the same direction while you descend down they are in a different direction. When the forces are equal and opposite you feel like flying, no forces acting at all and hence you feel like freely falling. This gives the sinking feel!

LIGHTNING

Lightning

Source : link

How is lightning formed?

Lightning is formed basically because of the electric charges in the clouds. The clouds are one of the most fascinating objects of the Mother Nature to observe at. They do not have a precise form.  It is also interesting to watch them move. What makes them move? It’s the wind on the earth’s troposphere that makes the clouds move.

What is a cloud exactly?A cloud is nothing, but is full of water in all of its three states i.e.

Water droplets (liquid)

Water vapor (gas)

Graupel (solid)

Now, what is a graupel?  Meteorologists believe that the graupel is the major contributing factor to the charges present in the clouds. Graupel is water in its frozen state or in other words water in its solid state. Then why not ice or snow, why is it given a special name? That is because, the meteorologists believe that these frozen particles in the clouds measure less than 50um. Though they are a solid matter, they cannot be seen even with a microscope. They are visible only under a powerful electron microscope.  Hence they cannot be categorized as a form of ice or snow and hence the special name GRAUPEL. In the process of water cycle, moisture gets accumulated in the atmosphere. This accumulated water in all its three states forms the cloud. The water particles in the cloud are at constant motion and get collided with each other when they move rapidly. During their collisions, electrons are knocked off and thus creating a charge separation. It is also observed that the lower portions of the clouds are always negatively charged and the upper portions are always positively charged. This is primarily because of the presence of the graupels. But how do these graupels create such a standard charge separation with the negative charges always at the bottom still remains a mystery!!!

Cloud – A Giant Capacitor

As the lower portions of the clouds become negatively charged, equal positive charges are created at the earth’s surface (because of induction of charges). Hence, now the positive charges on the earth’s atmosphere and the negative charges in the clouds are now separated by air. Hence, it’s like a capacitor with air as dielectric. The charges keep building. When the electric field created by these charges is strong enough to break the air, the negative charges from the clouds move toward the positive charges on the earth’s surface. In other words, a lightning has stuck!! 

Ionization of air

When the negative charges are formed at the lower surface of the clouds, the elements of the air immediately next to the cloud particles gets ionized i.e get separated into electrons and positive ions. Then the elements next to these ions get ionized. This is called induction of charges and the end result of this process is the creation of positive charges on the earth’s surface. Now, the air between the clouds and the earth’s surface i.e. the air between the charges are said to be ionized.  Ionization of air means that the electrons are now freer to move than the previous state, the neutral state, i.e. the state before ionization.  The ionized air is known as plasma. The air is the conductive path for the electrons to descend from the clouds to the earth's surface.

Step Leader

Once the ionization process is begun and plasma is formed, a path is not formed right away. In fact, many  paths of ionized air stem out from the cloud. there are usually many separate paths of ionized air stemming from the cloud. But the path with the least resistance wins. The electrons flow in that path which has least resistance. The path can be from cloud to cloud or cloud to ground. The path chosen by the electrons is called step leaders. It is because of this reason we do not see lightning as a single line but it looks like  root. The electrons choose their paths in all direction, with the only criteria which has the least resistance. The air is not ionized equally in all directions. Dust or impurities (any object) in the air may cause the air to break down more easily in one direction, giving a better chance for the step leader to reach the earth in that direction.

Streamer

As the step leaders are being developed and are in the way approaching the earth's surface, the electric potential on the earth's surface starts to increase. And therefore, electric lines of flux start from the earth's surface too as the step leaders start from the clouds. These lines of fluxes are called Streamers. When the step leader and the streamer meet the lightning is said to have been reached the earth's surface or in other words lightning is stuck !!! Also, it has to be noted that streamers do not occur in all the lightnings striking the earth's surface

Streamers

Source : link

It occurs only with the heavily charged clouds. In the above figure a streamer can be seen clearly. The bright line from the earth's surface to the cloud the streamer and a little less bright line from the cloud to the earth's surface is the step leader.

Why do we hear a sound (thunder) when lightning occurs?

Heat is always associated with electric current. Since there is an enormous amount of current in a lightning strike, enormous amount of heat is also associated with it. The heat generated is so large that a bolt of lightning is hotter than the surface of the sun.The white-blue flash that we see, is actually because of the heat generated. This heat energy makes the air around the step leader extremely hot. Immensely hot, that the air explodes as the heat energy expands the air. This explosion is what we hear as thunder.

Why is thunder heard after lightning?

Lightning and thunder actually occur at the same time. Light is very faster than sound. The velocity of light is 300,000,000 m/sec and that of sound is 331 m/sec. Hence, light reaches first and is followed by the sound(the thunder)

The lightning, results in heating up the atmosphere. The lightning can actually heat the area in the general vicinity to 20,000 degrees Celsius! (This is 3 times the temperature of the surface of the sun). Hence, the buildings on the earth's surface can easily be damaged and can even cause death to the living beings. Hence, we have to protect our self against lightning. The device used to protect us against lightning is called lightning arrester.

PACEMAKER

This is a X-ray image of a patient with an implanted pacemaker.

Source :Link

To start with let us define  pace maker as an electronic device that artificially makes the heart to beat. the heart has its own natural pacemaker. when it fails to work an artificial pacemaker is implanted. In the figure, you can see the image of the pacemaker removed from a deceased patient before cremation.

Where why and when is it used? How does it work? How can a human body work on electric current? In order to understand these questions we first have to understand the electrical system in human body.  

Electrical signals in the human body

You are moving your hand. Your brain sends commands to the muscles in your hand to move and hence your hand obeys. What is this command? How does it travel so quickly? It is because of electrical charges. Let us look in detail.

Pacemaker by Steven Fruitsmaak | Link

Inside the human body, electric charges are present. Without these electric charges a human cannot live. Any organ eye, nose, etc cannot function without electric charges or flow of electric charges (electric current). How are these electric charges conducted throughout the body or in simple terms how does the flow of these electric charges occur? The nerve cells conduct these electric charges. Because of which we can think, remember, and make decision, act, react and so on. If we speak, listen and watch it is because of those electrical signals. These signals are called action potential.

Our body is made up of millions and millions of cells. Every cell has various constituents in them like proteins (made of an acid called amino acid), carbohydrates (made of carbon, hydrogen). But, a common characteristic of every human cell is as follows. The inside of the cell is always negatively charged and outside the cell is positively charged. The charges are separated by the cell wall. This potential that is present on the boundary of every cell wall is called resting potential. The positive charges are because of sodium and potassium cations. The following figure depicts resting potential

There is always a balanced state towards which all human cells work i.e. to ensure more positive ions remain outside the cell. In other words they make sure they always have resting potential. When you touch a pen, it is your brain feeling it. Hence, there is a messenger carrying this signal to the brain that you have touched a pen and your brain acts accordingly lift it or start writing. As your fingers touch the pen, there is a change in the charges in those cells that come in contact to the surfaces of your finger. The positive ions move inside and the potential changes and this potential is called action potential and now the cell is said to be depolarized.

 Because of induction of charges the adjacent cells also undergoes the changes as shown in the figure below. Likewise, the depolarization happens throughout the nerve cells that connect your finger and the brain. As this action potential reaches the brain or when the brain cells get depolarized they recognize it is a pen and send commands to the fingers.

This is how electrical signals travel in the body. There are charges present in the heart too. Electrical charges in the heart conducts in the same way but not through nerves. Let us look in detail.

Electrical system in the heart

To understand the electrical system in the heart let us discuss the working of the heart in brief. The heart is a muscle that works continuously like a pump.Heart is located at the centre of the chest tilted lightly towards left hand side. It is hollow and is divided into four chambers namely

1. Left atrium
2. Right atrium
3. Left ventricle
4. Right ventricle

as shown in the figure below. Each beat of the heart is set in motion by an electrical signal generated inside the heart all by itself. In order to understand the electrical system of the heart let us discuss the

working of the heart in brief

Working of the heart

The right atrium receives impure blood (de-oxygenated blood) from all parts of the body and the left atrium receives pure blood (oxygenated blood) from the lungs. When the atria are full with blood, they contract and hence a pressure is generated. The right atrium contracts first and then the left atrium. Hence there is a time delay between the two atrial contraction. This pressure is called systolic pressure and  forces the valve between the atria and ventricles to open and hence the blood flows into ventricles. When the ventricles are full with blood, the ventricles contract.

  

Heart diagram by ZooFari | Link 

The pressure developed due to the contraction of ventricles is called diastolic pressure. The right ventricle pumps impure blood to the lungs and the left ventricle pumps pure blood to different parts of the body.In the figure above the impure blood vessels are red in colour and pure blood vessels are blue in colour. From the working of the heart, it is clear that the blood is pumped because of the pressure created due to the contraction of the atria and ventricles. How do the contraction occur? It is because of the electrical signals in the heart, the contraction is happening. These electrical signals originate in a node called sino-atrial node also called as SA node as shown in the figure below. You can see the SA node in the right atrium.

When a cell that is negatively charged becomes positively charged it is called depolarization as already discussed. Depolarization in the heart begins at the Sino-Atrial node also known as SA node. SA node cells can depolarize all by themselves and this action is called automacity .Once the SA node cells are depolarized, the neighboring muscle cells start getting depolarized shown by red arrow around the SA node. This wave of depolarization now spreads through Bachmann's bundle to the left atrium. The atrial contraction happens because of the depolarization of the cells. The cells in the heart are called myocytes and have this special characteristic feature to get reduced in volume when they are depolarized. This happens because of the movement of calcium, potassium and sodium ions inside and outside the cell thereby decreasing and increasing its charge. And correspondingly, the volume changes and hence the contraction and expansion of the atria which leads to filling of blood inside the atria and then being pushed into the ventricles.

Recollect that there is a time delay between the left and right atrial contraction. This is because the electrical signals are generated in the SA node in the right atrium. It takes time for these electrical signals to travel to the left atrium through Bachmann's bundle. Hence the right atrium contracts first and then the left atrium. These signals also travel to another node called Atrio-Ventricular node also called as AV node from the SA node through the path called inter nodal track as shown in the figure above. The distance the signals have to travel from the SA node to AV node is more than the distance they have to travel from SA node to the left atrium. Hence the contraction of ventricles happen after the left atrial contraction. 

From the AV node, the signals travel to the walls of the ventricles through bundle of his as shown in the figure. Also, the right ventricle receives the signals first and then the left ventricle. Hence the contraction of right ventricle happens first and then the left ventricle. Hence the order of the contraction of the heart muscle or the order in which electrical signals are received by the heart muscles is as follows

• Right atrium
• Left atrium
• Right ventricle
• Left ventricle

The ECG Electro-cardio Gram, is the recording of the measure of these electrical signal. If you observe an ECG, there are four main waves that are due to the depolarization of the atria and ventricles.

sinus rhythm label by Agateller (Anthony Atkielski) | Link

Here, the waves are the measure of the electrical action in the heart

P wave - depolarization of right atrium

R wave - depolarization of right ventricle

T wave - re-polarization of right ventricle

The PR interval is very important in designing the pacemaker and is the delay between the atria and ventricle depolarization and is 0.2 sec.

The following animation depicts the working of the electrical system in the heart

ECG principle by Kalumet | Link

Now that we have understood the generation and conduction of electrical signals in the heart let us now give pacemaker a proper definition and understand its working. Heart rate is the number of heart beats per minute. When the human body is at rest, the heart rate in adults is 60-80 beats per minute. In other words the SA node generates electrical signal to depolarize the cells 60-80 times in a minute. Hence every cell in the heart depolarizes 60-80 times in a minute. A normal healthy heart has its own pacemaker, the SA node that generates the electrical signals for the heart to pump blood. The heart is in need of a pacemaker under following conditions

Bradycardia – a condition in which the heart beats too slowly - less than 60 beats per minute

Tachycardia - a condition in which the heart beats too fast - more than 80 beats per minute

Atrial fibrillation – the upper chambers of the heart beat rapidly

Heart failure – a condition in which the heartbeat is not sufficient to supply a normal volume of blood

When the above conditions are left untreated, the patient may eventually die. hence to treat the condition or disease, an artificial electronic device is surgically implanted to regulate the heart beat. Such an electronic device is called pacemaker. On the whole, a pacemaker is required if the entire electrical system or a part of the system fails.

What is a pacemaker?

A pace maker is a small device that is implanted under the skin, most often under the collar-bone on the left or right side of the chest. Pacemaker continuously monitors the heart and if it detects a slow rhythm or an interrupted rhythm it sends electrical impulses to make the heart beat normal. As shown in the first figure pacemaker have thin, soft, insulated wires called leads to carry the electrical impulses from the pacemaker to the heart. Pacemaker is designed to mimic the heart's natural pacemaker, the SA node. Pacemaker has two purposes namely

• Pacing
• Sensing

The most popularly used pacemaker nowadays is the dual chamber pacemaker. A dual-chamber pacemaker typically requires two pacing leads: one placed in the right atrium, and the other placed in the right ventricle. A dual-chamber pacemaker monitors (senses) electrical activity in the atrium and/or the ventricle to see if pacing is needed. When pacing is needed, the pacing pulses of the atrium and/or ventricle are timed so that they mimic the heart’s natural way of pumping. It comprises of three parts: an electrical pulse generator, a power source (battery) and an electrode (lead) system. The electrical pulse generator consists of the following components: a sense amplifier circuit, a timing control circuit and an output driver circuit (electrical impulse former) as shown in the figure below

The electrodes give the electrical activity of the heart. After the sense amplifier amplifies the signal, a comparator compares the signals received from the electrodes to the one already stored in the form of voltage signal. If the signal received is the same as that of the reference voltage, then the heart is normal and no signals are sent. But if it is low or high, then the pulse generator starts sending signals till the heart's activity returns to normal. A timing control is needed to control the time difference between the pulses to the SA node and AV node which is 0.2 sec.

This is a very basic working of the pacemaker. In the modern era, the pacemakers with microprocessors and transceivers are under research. These modern pacemakers fit into the application called tele-monitoring of patients where the patient monitoring system is linked to the satellites and the doctors can get updates of their patients' condition from any part of the world. Such pacemakers record the history of working of the heart and its electrical activity and transmits data when in need.

MAGLEV TRAINS

Magnetic levitated trains are abbreviated to maglev trains. Maglev trains do not have engine to pull the train cars rather they use the basic principles of electromagnets.

What are electromagnets?

Any current carrying conductor (e.g. wire) has a magnetic field around it. It loses its magnetism when the current is turned OFF. Electromagnet is a coil of wire. It is usually wound on an iron core with many turns lying side by side. This is done because; the strength of the magnetic force produced depends on

• the number of turns of the coil
• the amount of current.

Hence more the no of turns more is the magnetic field. The poles of the electromagnet can be changed by changing the direction of the current.

What are maglev trains?

Maglev trains are trains which are suspended, guided and propelled (moved forward) by magnetic forces. The track of the maglev train is called the guide-way. Working of the maglev trains can be studied under the following

• Levitation
• Propulsion
• Guidance

Levitation

            Maglev trains have no contacts with the rails while they move forward. They are levitated on the guide-way with the help of magnetic forces. Levitation is the process by which an object is suspended against gravity in a stable position without any physical contact.

Magnetic levitation is used based on the property (1) that “The force between two magnetic bodies is directly proportional to their magnetic moments and indirectly proportional to the square of the distance between them”. Hence, while the magnetic levitation is designed, the major factor to be considered is the distance between the train and the guide-way.

There are two types of levitation used in maglev trains namely

• Electro Magnetic Suspension (EMS)
• Electro Dynamic Suspension (EDS)

Electro Magnetic Suspension (EMS)

            Like poles repel each other and unlike poles attract. This is the basic principle used in EMS. The electromagnets are placed under the train and in the guide-way. The electromagnet on the guide-way repels with the magnets under the train and hence the train levitates. The levitating gap is kept as small as possible to have greater magnetic forces according to the property (1) discussed earlier. The levitating gap is usually 10mm with passengers onboard. While the train is moving, the electromagnets are magnetized and when the train has to be stopped, just the current is turned off to demagnetize the magnets. The train stops and rests on the guide-way closing the gap.

The magnets are placed in the form of C under the train. The  repulsive force acts on all the three edges of the C-shape and helps in better levitation.

The major factor to be considered while designing the magnetic strength is the earth’s gravity. As already mentioned, the magnetic strength depends on the amount of current. Hence, to make the train levitate against the gravitational pull, large current is required to create a strong repulsive magnetic force. Study shows that to maintain a gap of 50.8 mm 50,000 ampere turns of magnetic strength has to be supplied.

Magnetic intensity (strength) = N × I

Where,

N – Number of turns of the coil

I – amount of current

Hence, to maintain a gap of 50.8mm in a coil with 1000 turns (assumption) 50 amperes of current has to be supplied.

The train moves at a speed of 400 km/hr. The maintenance of a very small levitating gap at higher speed using EMS is challenging. The monitoring and control of the gap is very difficult at higher speed. Hence, higher speeds cannot be achieved in this design.

 Electro Dynamic Suspension (EDS)

EDS was discovered by Japanese while EMS by Germans. By using EDS, much higher speeds can be attained. The fastest train running in the world uses EDS principle and runs at a speed of 581km/hr. However the train has to be run on wheels till it gains a speed of 100 km/hr, only after which it can be levitated. In this system the track is called inductrack.

Electro dynamic suspension system has electromagnets on the train. The inductrack has an array of electrically shorted circuits (coils connected in series from the start of the track till the end). According to Faraday’s law of electromagnetic induction, whenever there is a change of flux linked with the coil, an emf (current) is induced in the coil. When the train starts to move on its wheels, the magnetic flux linked with the coils in the inductrack changes and hence an emf (current) is induced in the coils. As already discussed, every current carrying conductor has a magnetic field around it. Hence, there is a magnetic field developed around the coils in the inductrack. This magnetic field opposes its cause i.e. the magnetic field in the train (by Lenz’s law - when a current is induced in a conductor it is in such a way to oppose the cause). Therefore, a repulsive force is produced between the magnetic field of the train and the track and the train levitates.

The electromagnets in the train are superconducting electromagnets. Superconductors are materials whose resistivity (Resistivity is how much a material opposes the flow of current) becomes zero when they are cooled to critical temperature. Critical temperature is the temperature at which the matter has no distinction in its states. For e.g. at critical temperature of nitrogen, nitrogen is neither a gas nor a liquid, but has both the characteristics of gas and liquid. Superconducting electromagnets are used as the coils of these electromagnets can carry huge amount of current as the resistivity is almost zero. Hence, the magnetic force is higher and hence higher speed is achieved.

Here, as the power is supplied only to the electromagnets in the train, this system consumes less power compared to EMS system. In EDS system the levitation gap is 10 cm. Though the distance between the two magnetic bodies is larger, the magnetic force produced is huge because of the use of superconducting magnets. Therefore, this system does not require any control and monitoring of the levitating gap.

 Propulsion

Propulsion is moving the train forward. To propel the vehicle, the electromagnets are placed on the sides of the guide-way.  They are energized according to the time when the train reaches that particular spot and are de-energized the rest of the time.

Maglev propulsion by Cool Cat,Stannered available at http://en.wikipedia.org/wiki/File:Maglev_Propulsion.svg Under a Creative Commons Attribution-Share Alike 3.0 Unported license

In figure, the train is pushed due to repulsion of south poles and is pulled due to attraction of poles. So the train moves forward. Now the next set of pole comes into action and thereby a continuous motion is produced.

 Guidance

The propulsion coils are used for guidance. The propulsion coils are placed on the left and right side of the guide-way.
Emf is induced in the coils when the train is moving, the same principle on which EDS works. The coils are connected and hence the emf on either side of the train are opposite in direction. Hence, they cancel out each other. Thus the  train moves in the centre of the guide-way. When the train deviates from its centre position i.e. when it moves towards one of the walls, one of the emf is greater than the other and the resultant emf directly depends on the difference in distance. As, there is an emf, a resultant magnetic force is also produced. Hence, the magnetic force due to emf depends on the difference in distance. This resultant magnetic force called the guiding force pushes the train to the same distance and thereby putting in the centre.

Maglev trains are mainly used for transportation in china, japan, germany,etc. It is still not used by many countries. This article has just briefed the basic principles and working of the maglev trains.  Maglev trains are the best example of the modern transport means.

If solar panels are installed above the guide-way all the way along in maglev trains, they can also help in saving world resources!