The Mystery of Force Fields!

The day was little breezy. Professor Govind was busy soldering the transistors on his new invention. The television was switched on and Sheela was there easing on the sofa, watching an episode of "Star Trek". It was indeed a nice episode. An asteroid was heading towards the small space ship in terribly high speed. The crew felt the danger of the asteroid hitting the space ship. Everyone was puzzled.

The captain shouted "Shields up!"

No sooner he shouted, than a thin bluish layer enclosed the space ship. It shattered up the asteroid into pieces then.

"Phew!, that's the end", exclaimed Sheela in amazement. "Professor, what actually is a force field?"Sheela's question attracted his attention. He started then, 

" Force fields are thin impenetrable barriers which could destroy or reflect everything that fell on them. Be it a stone, metal piece, water or even laser."

"Just have a look at this photograph. It looks like this", he showed her.

"The principle behind this force field is a simple theory. You might have seen your Plasma television screen. The same goes here- the principle of isolating air from vacuum", he paused to take out something from his junk box.

"Oh!, But Professor,what is that we call "plasma"? interrogated Sheela.

"I'll rather show you off", said Prof.Govind and took a hollow glass sphere, in which a metal electrode is inserted. He said, "Sheela, this glass bulb contains a mixture of Helium and Neon gases at very low pressure," while connecting its terminals to 5000V a.c. supply of high frequency(about 35 kHz). The bulb started glowing and violet streaks started appearing in it.

"Wow!" wondered Sheela.

He said, "Before the matter inside the bulb were in gaseous state. But, as soon as we started applying electric potential, the gases will be ionized completely. And this state in which gases are completely ionized is called "Plasma state" the forth state of matter" and touched the glass bulb. White streaks appeared from the filament to the point where he touched the bulb.
"Is there any chance that I get shock while touching this bulb, professor?" asked Sheela."Actually the glass here behaves are dielectric between the ionized air inside and my hand(both being a conductor, this setup behaves like a capacitor). 
Leaving this setup intact, he took a strong horseshoe magnet and placed it near iron filings. Sheela smiled and said, "I knew that magnets attract charged bodies already in my grade-5". 
"That's the matter. So we have ions that are charged, haven't we? Just imagine that this magnet attracts these ions completely to one side thereby creating vacuum at the center.We get a plane of ionized gases on the corner." 
The same principle is used in plasma windows.


"This plasma window can be used in combination with a series of laser curtains and carbon-nanotubes to generate a powerful force field around us. But to stop laser, one must deal with photochromatics", said Prof.Govind.
"Photochromatics?" interrogated Sheela.
"Yeah. It is the science based on the fact that certain materials can exist in two different forms. Say your sunglasses. How does it become black on exposure to the sun?" puzzled professor Govind.
"How?" asked Sheela. 
The glass is coated with a thin film of photochromatic materials which when exposed to radiations like UV rays becomes dark(colored) due to a change of state. Similarly, specially designed material has to be used to selectively stop lasers or else, you'll go blind on dark while you're in force fields."


"Hmm. That was interesting!" exclaimed Sheela. "Anyway, it's time for the dinner. Thank you professor. I must go now." 
"It's been a great time explaining you about this. Pleasure!" said the professor and got back to his workshop.

Anti-gravity

One day, Sheela wanted to ask some doubts on superconductors. She decided to approach prof.Govind in his laboratory. To her surprise, he was floating in mid-air defying gravity. She was astonished and ran out of words. She forgot why she'd come there and asked," Professor, How could you do that??!!!".

He jumped from mid-air and smiled at her. "Well, If a magician could do that, why can't I?"

"A magician performing anti-gravity trick"

"Super-conductive magnetic levitation is a wonder science which has made a remarkable mile-stone in the history of Science. There are two notable changes that occur when a material changes into a superconductor, namely

#1. Electrical resistance becomes zero.

#2. Magnetic lines of force are excluded from the material.

And these all happen for certain metals at low temperature only.Hope you might have heard about "Meissner effect".

When a superconductor is placed in a weak magnetic field, the field penetrates only a small part of the material(order of few micrometers). Just look at these pictures depicting Meissner effect", said Professor Govind.

"Meissner effect is a state of perfect diamagnetism in which, the magnetic field within the material of the superconductor is zero(B=0). This leads to the condition that the magnetic susceptibility is -1.

Whenever a magnet is brought near diamagnetic materials, they themselves become magnetized so as to oppose the external magnetic field. This is extreme in this case. You might be knowing that water is diamagnetic and this fact has helped scientists to levitate a frog applying a high magnetic field of "15 tesla", added him.

"That sounds interesting", exclaimed Sheela.

"Just watch what I'm doing. I'm pouring liquid nitrogen which boils at -196 degree Celsius so as to bring this metal piece to its superconduction state. It's always pleasure to watch how it levitates.

By now you could have understood the secret of anti-gravity and how I was floating in mid-air earlier", asked professor Govind.

"Hmm..That's true..and interesting too."

Power from Fruits!

One fine day, Professor Govind was doing some experiments on Quantum teleportation. Sheela entered his lab and found some cut fruits on the table. She thought that Govind must have cut the fruits for his breakfast. She asked, "Professor, the law is the same for all, isn't it?

"Yes, no doubt" said professor Govind.

Sheela sarcastically asked him, " Haven't you shouted at me not to eat something in the laboratory?? Then, what these freshly cut apples and lemons have to do in your laboratory?" 

Govind smiled at her and said, "Oh! These fruits are the food for these multimeters and LED's."

"Food for them!" screamed Sheela. "But how?", she asked.

"Well, I can explain you. Different types of fruits have different electrolytes(ions) in them, especially, lemons and grape fruits have acids like ascorbic acid, citric acid, ions and NADH(Nicotinamide Adenine Dinucleotide Hydride generates cellular energy). When electrodes are inserted into them, these ions migrate to the appropriate electrodes generating current.

He took an apple and inserted two electrodes, a copper electrode(cathode) on one of the sides and a Zinc rod(anode) on the other side. He connected these rods to a multimeter and it was found working. Then he replaced multimeter with an LED(Light Emitting Diode) and showed that it lit up. But the light doesn't last long. It was slowly becoming dull and finally stopped glowing.

"Oh! So, fruits produce current that won't last for even 5 minutes, yeah?? Then what's the use professor?" asked Sheela. "Hmm. Nothing, I suppose. They produce only a few current(about 2 volt) and stops as soon as all the electrolytes have been used up completely. However few more lemons connected in series can serve as our regular batteries. Also potatoes produce a few more volts than fruits. So, this is a bit economical than ours", said Professor.

"Economical?? Well, what do you mean? Don't you know that these lemons cost more than a common battery? Sound that you haven't been to the city markets, right?" laughed Sheela.

"Hmm..I didn't make a note of it. Err, I think it would help a lot in any village in an under-developed countries, where there's no availability of neither electricity nor batteries", said Govind.

Invisible Liquid!

It was 28th of February, the National Science Day. Sheela was wondering what could she present on the eve of Science exhibition arranged in her school. With no other thought, she decided to approach professor Govind. No sooner she opened the laboratory, she was puzzled. Professor was inflating some balloons. 

She asked him whether he's turned a baby with sarcastic undertone.He welcomed her and asked what can he do for her.She explained her situation and requested him to guide her with a science fair project.

He asked, "Why shouldn't you do this?"

"This!! Professor, I'm sure that I ain't a baby," shouted Sheela.

Govind said, "Hmm, say that you're familiar with helium balloons".

"Professor, I know that helium is lighter than air and hence a balloon inflated with helium floats to the top; what's new with this??" asked Sheela desperately.

Now professor didn't speak anything and went to the junk box and took an empty glass fish tank. Then he started doing something. "Professor, I was asking about my science project, please", Sheela said. Professor never uttered any words and was keen in his job. Sheela watched what he was doing.

(watch the video)

Sheela
could not speak for a moment."Woww!Invisible liquid" she exclaimed.
"So, how about you doing this for your science fair, Sheela?" asked
professor. 

"This is excellent professor. Explain me how it works", asked Sheela.

"The principle is nothing but what you explained me earlier. Density matters..." smiled Professor.

He
continued,"I just closed this tank with a wooden board and filled it
with Sulphur hexafluoride gas. Sulphur hexafluoride is roughly 5 times
denser than air. Lighter gases tend to displace heavier gases downwards.

Hence SF6 displaces air upwards".

"Thousand thanks for you professor," greeted Sheela.

"But be careful.This gas is much poisonous and also a green house gas", explained Professor.

Magic-Sand

Magic sand - one of the most rated party tricks of the decade is worth watching.  Just check out the video here.

 Magic sand or Mars sand or moon sand or aqua sand or whatever it is called, is a direct outcome of a special law of Physics - Hydrophobicity! It is never wetted by water.

Hydrophobicity is the property of objects by virtue of which they repel water. (hydro-water, phobic-fear) The substances which repel water are called as hydrophobes or water repellents.

First let's know what the so-called magic sand is made of. It is made up of usual beach sand coated with some hydrophobic substance, usually trimethylsilanol. This trimethylsilanol is an organo-silicon compound. Like any other organosilicon compound, it acts as water-repellent.

How it works?? Let's see.

Usually a water repelling (hydrophobic) substance is a non-polar compound which has a greater tendency to combine within themselves and so, they do not readily bond with other compounds. In other words, their adhesive force is very less than their cohesive force. Not only water, but they repel all polar compounds to different extent.

Water, a polar molecule exists as a liquid due to inter-molecular hydrogen bonding. Since oxygen is highly electronegative, it attracts the shared pair of electrons towards itself and acquires a small negative charge. On the other hand, hydrogen atoms acquire a small positive change. So, hydrogen having a small "+ve" charge naturally attracts oxygen having small "-ve" charge as "unlike charges attracts each other". Thus all water molecules are associated. There is no chance for interaction between water and non-polar covalent molecules as the atoms do not differ much in electro-negativity. They are usually neutral compounds and so, there is no chance for interaction with water molecules which are electric dipoles. At the same time, they are strongly bound to themselves so that they repel water.

Initially this "Magic sand" was developed so as to degrade ocean spills. When it is sprinkled on sea water, it mixes with oil and settle down the ocean floor as the mixture becomes heavier. The point is they are not wetted by water, but can be wetted by oil, where oil is a non-polar compound.

It is widely used as a trick. Under water, they appear shiny, why because, when they are made to submerge in water, they gather a thin film of air around themselves.

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Ping Pong Ball Magic!

Now this summer vacation is the time for doing some weird and interesting scientific experiments. 
Just take a ping pong ball and use a long straight pin to puncture it so that there is tangential hole on it.

Now take a beaker full of liquid nitrogen and use tongs to immerse the ping pong ball into beaker so that it stays in the middle of the beaker, for 1 minute or so.

 Take the ball out and gently place it on a table. It starts spinning at a high speed. Check the video!

Exciting to see and do, isn't it??


But why it spins?? Let's check it out~!


When you immerse the ball into liquid nitrogen, nitrogen gets inside the ball. Liquid nitrogen exists at a very low temperature of around -200 degree Celsius. When the ball is placed on the table, liquid nitrogen gets heated up and gets converted into gas. This gas rushes out at a high speed due to the high pressure inside the ball. The gas comes out through the small tangential hole with high speed. By Newton's law, the ball experiences a equal and opposite force. Any force acting on a spherical body along a tangent tends the body to spin. Hence the ball spins.


As it spins, it gets heated up due to the friction between the table and the surface of the ball . So, the speed of the ball increases for a while and the decreases as the pressure inside the ball decreases. 
Try doing this in your science lab. Sure you will like it~!
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The video has been taken from the net and the picture has been taken from a site and altered for better understanding.


Discussion on this article awaited. Please post as a comment.