Thursday 16 July 2015

How a semiconductor diode(pn junction) works




Below is a very straight forward diagrammatic explanation of how the diode works.



A diode is just a p and n type semiconductor material joined together.
As soon as the junction is made, there will be a rush of the charged particles. The majority and minority carriers from n region will rush into the p region and the same from p region will rush into the n region. They are the carriers of the current. Now, the minority carriers too transport themselves and the reverse current and the forward current is equal, its just a basically rush of the particles moving from their own respective region to the other region simply because they dont have anyone to stop them. They are badass people. But with no actual use. The total amount of current will still be zero. Hence, if there is no external bias, there will be no current. Cool makes sense. Also, it might seem illogical for the elctron from n type material to actually go into the p region, although they have to overcome the attractive forces, they have still enough kinetic energy.The current her is called diffusion current.

But the rush is limited to only a certain region. The entire block of our material isn't going to be affected and technically replaced, but a small region near the junction. Hence the depletion region being formed as shown in the figure.

Now a bias is applied, positive bias. The relevant charged particles will be pushed, the depletion layer will be reduced and the current will flow. For the reverse bias, the depletion region will expand giving no chance for the charged particles to move hence no or very little current. The current under bias is drift current.

Youtube links-
https://www.youtube.com/watch?v=JBtEckh3L9Q
https://www.youtube.com/watch?v=OyC02DWq3mI
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Friday 10 July 2015

Religion.

Few days earlier. Results were to be announced anytime. Tensed, is the word too small to describe our situations. Every classmate of mine were worried and at the same time anxious about the results, scribbling through the college website and every now and then checking mail. It was around that time when I noticed something strange about my friend’s whatsapp dp.

It was a picture of Lord Shiva carrying a “damru” with one palm towards the screen. I laughed off. The reason was obvious. I took a screenshot of it and teased him about it. He said keeping that dp was “lucky”. I didn’t understand the logic. In fact I never do.

I don’t fully know what religion is but at the very least, it isn’t about keeping a God’s photo as YOUR display picture only around the time of results.

Hinduism very passionately includes worshiping of stones and cows, keeping widows in seclusion and hatred, marrying with a tree or fuck whatsoever. One fine day when we were to visit Tryambhakeshwar, a one of the 12 “Jyotirlings” of Lord Shiva. For those who don’t know, Lord Shiva, one of the trinity is supposed to reside in 12 places all over the India.

“Why did he chose ONLY India to cast his presence if he is the sin destroyer of the entire WORLD? Moreover why do all Hindu Gods chose only India to take birth?” asked my rational Uncle.

The question very appropriately, in itself, answers many other questions. Indian Gods were born only in India. Japanese Gods were only in Japan. Ahh well, Christians are a bit universal for the matter. If even, we were to think that they all were incarnations of the same single creature why did they advertised different ways to reach God?

They didn’t advertise anything. The different people requires different sets of rules, hence the different religions. Period.

Sati was banned by Britishers. Did the whole world die? No. Following this, how many more traditions can we remove by enforcing a law? Think about it. The biggest proof of blind faiths being illogical, irrelevant and ineffective is that they are followed in different styles in different lands. We consider crossing of a black cat a bad omen while some finds it lucky. Ohh wait, that just now reminded me of the origin of the “black cat crossing bad omen logic”.

Once upon a time, very long back, kings, businessmen who had to travel across cities even in nights faced a very inadvertent trouble in their bullock carts. Bulls when crossing deep forests, when encountered with a black cat turns horrified at the sight. It’s because the eyes of a black cat glows bright in dark which leads bulls to frighten. After the discovery of this fact, it was suggested that the travellers’ should rest for a while when their carts get crossed by a black cat. News spread carrying along with it several masala’s and result is something which is evident at present.

But still I don’t intend to hurt any of the sentiments. If this is what keeps you a human, it’s fine. If you believe that throwing a polythene full of flowers in to running water will bring you fortunes  it’s fine. It at least brings you hope. But do think of what your actions actually result to. Water contamination. But I say, it’s fine. Remember the film PK? It cleverly portrays how religious beliefs brings a lot of positive hope in your heart and a will to fight this world. “Somebody is there to protect me. I have done my job to make him happy, and now it’s his turn.” This thought itself is miraculous in everyday life, to keep you “going”.

There is a very popular story about a business man. He was having a bad time, his company was in huge debts and the trade wasn’t going well. He was thinking of every possible way to prevent his company to go bankrupt but couldn’t. One day he was walking alone a road distressed as usually, decided to sit on a bench, it was then an old man approached him and seeing his bad mood asked what the matter was. The businessman narrated his helpless situation. The old man seeing the man extremely sad took out a cheque and handed him over saying that the man can return the money in one year and will meet him at the same place then and went, The businessman was shocked at the gesture but was even more shocked when he saw the cheque. It was from Warren Buffet and the sum was 1 billion dollars! He was overjoyed. Now all his problems were solved, but suddenly his conscience struck him. As a man with self-respect he couldn’y just accept the favour. He decided to not just withdraw the money but to keep it for future security. He decided to simply forget about the cheque and concentrate on the business. He tried hard, made better deals, assured client satisfaction, soon in less than six months. He had kept the cheque safely all this while and eagerly waited for the day to come when he could return the cheque just as it was. Finally, the day came and he saw the same old man sitting on the bench but as soon as he started to move towards him, a middle-aged woman came and started to pull Warren Buffet from his sleeves! He got anxious and asked the woman who see was and how could he behave like this to such a personality?! The woman just gave him a grim look and told him that he is no special, he was just his father who is a mental patient and just roam about calling himself Warren Buffet!

What was it which made the business man to come back on track? Hope. Hope that there was something he could use as his last resort if anything goes even worse. His self-respect and courage made him try his best to not actually use it. This is what religion brings to one’s life. As long as it brings hope to you, it is legitimate for you to perform religious actions. We cannot stop you from doing something which doesn’t harm living beings, but sadly your actions does. (Aquatic animals)
But there’s a hack. Pay your taxes regularly so that water you just spoiled gets cleaned up. It’s gonna be cleaned up anyway. Pay for roads to be cleaned where you kept a coconut and a “lal chundhi”. Rituals say you to keep it, not to protect it and make sure to make it last till eternity. But once again I’ll tell you, this all stuff isn’t necessary. They are to religion what add-ons are to your browser. “Extras” To make your experience complete.

But, I don’t really hate religion. It’s something which keeps these monsters civilized. Yes. We are monsters who are simply trained to be civilised. Otherwise there are tribals who eat each others. If we would look closely into some rituals, we will find them necessary for the overall stability of the world. They were meticulously planned on to implement. Stories which Hinduism teaches, no doubt contains lessons which are pure genius. We should respect them. We should follow them. My parents say, “how can someone create stories so intimidating, so consequential, so real?”

“What?” I say, “don’t you watch movies, TV series? The fictional stories they say, aren’t they simply spectacular with so much of variety and fresh content every week? “

Then there is no reason to doubt the ability of our ancestors to woo stories especially when they were supposed to inculcate values not only in their present but also the future generation. Maybe there was no one with an elephant face with two wives and still no children(Why?) It’s always funny to ask, why isn’t there any progress to Gods and their families?

We spill milk in lakhs of litres on a stone, to make our day good not realizing that if we would have donated it, that same one glass of milk could have actually made somebody’s day good. They, in very specific manner what is termed as “defense”, say that science hasn’t yet found many answers. Yes, but that doesn’t mean you will roam around following some manuscripts written over thousand years ago. Science has answers now, to those questions which were considered “unanswerable” earlier. Predicting disasters, curing mental diseases(do I really need to tell what religious people have an opinion about this?) and many things which were considered to be in the religious domain.

But,

If we should not believe in religion, what should make us in control?

First of all, you should consider yourself extremely lucky that you were given a life or may be your parents had a beautiful night that date. But, err you still are lucky. Furthermore, you have two legs, two arms, two eyes, a mouth, two ears and a caring parents who shower their love to you. A mom who destroys her own youth to make yours better. Omg, you are complete! And mind you, you are still lucky enough to have these bare minimum.

Second step, follow your religion. Yes, be aware of what it actually is. Read every books. I am telling you Bhagwad Gita. Ramayana and Mahabharata are epic. Not just because they are called “epic”, but they actually are. If the customs and beliefs satisfies your thoughts, follow it. But don’t fall prey to blind faith. Cross examine everything but remember again, some things really take time to fully understand. But if not, try another or may be nothing.

So you decided to follow nothing? Chill, it’s not a sin but wait you are already above this stuff. You just saved a lot of precious time of your life. Now you are supposed to not think of Gods but think of your future generation yet to come. You are now responsible to make your world worth living for others. The world given to you is beautiful and you are here to make it even more beautiful. O live in present to the fullest rather than shedding tears on the past. Many of times we cry over our past for which we could actually do nothing about. It was probably bound to happen, think it this way. Don’t remind yourselves that you did a mistake, instead pledge a vow that you will never do it again. Don’t think about what will happen in your future, instead strive for ways to improve it. Don’t worry too much about making the right choices. Nobody knows what is the right decision to make, life’s all about making a decision and then trying to justify it to be right enough. Never give up, it takes years for one to become an overnight success.

And one last thing,

If you are a religious person, don’t think every atheist got a license to kill.
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