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.