TRANSISTOR-THE KING OF ELECTRONICS

We know, the flow of electrons is electric current. Electrons are said to be negative charge carriers.

In a molecular structure, if there is a vacancy for an electron, it is called hole. When an electron from somewhere in the structure fills-up this hole, a new hole will be created where the electron has just left. Hence a hole can move opposite to the electron. So the holes are said to be positive charge carriers.

In a germanium crystal, arsenic is infused. We get electron rich material called N type (negative) material. When boron is added to germanium, we get holes surplus P type (positive) substance.

A thin P type material is sandwiched between two N type material. Now a transistor is made. These three pieces NPN are respectively called emitter, base, and collector.

By connecting negative of the battery to the emitter(N) and positive to the collector(N), the electrons can be pushed from emitter and pulled at the collector. On the way, through the base(P) some electrons combine with holes. So some electrons are lost in the base. But most of the electrons reach collector resulting in collector current.

By applying suitable negative voltage to the base, we can control the quantity of holes in the base region. consequently the loss of electrons flowing through the base and the collector current is also controlled.

In a nutshell: By varying small voltage that is applied to the base, one can produce big variations in the collector current. This is amplification, main function of transistor.

Example of one application: Microphone(mic) converts voice into electrical signals. These small varying electric voltage is fed to the base of the transistor. Then we get large varying current as output from the collector. It is then supplied to a speaker which produces big sound.

So many transistors are present in all the electronic gadgets. In the CPU of the computer, millions of transistors is present.
At present : No transistor, no electronics.

Note: PNP transistor is also possible.

Comments

LISSAJOUS FIGURES

Definition: "When a particle is subjected to two sine wave motion or two oscillatory motion at right angles, the particle describes lissajous figures". We know sine wave motion and circular motion is basically same. Hence we draw two circles A and B perpendicular to each other. The circle B rotates twice faster than circle A. That is, frequency of circle B is two times than that of A. A particle at the intersection of two circles is subjected to two sine wave motion A and B at 90 degree simultaneously. The particle will describe figures depending on the frequency and phase of A and B . In our case, the ratio of frequency is 1:2 and the two waves are in phase. To draw lissajous figures : A moving point in both the circles are chosen. Here we should remember; during the time taken by the circle A to complete one rotation, circle B completes two. Hence the points are marked on the circles according to their speed. Then straight lines

THE PARABOLA

A jet of water shooting from a hose pipe will follow a parabolic path. What is the so special about parabola. Y= x^2 Draw a graph for the above equation. It will result in a parabola. This parabola is also called unit parabola. Any equation involving square will yield a parabola. Example: Y = 2x^2 +3x+3 (also called quadratic equation) X= 2 and -2, both satisfies the equation 4 = X^2. Parabolic equations always have two solutions. Any motion taking place freely under gravity follows parabolic path. Examples: An object dropped from a moving train, A bomb dropped from flying plane, A ball kicked upwards. If a beam of light rays fall on the parabolic shaped mirror, they will be reflected and brought to focus on a point. This fact is made use of in Dish Antenna, Telescope mirrors, etc. Inverted parabola shape is used in the construction of buildings and bridges. Because the shape is able to bear more weight. A plane

CASINO'S GAME

Let us find out how the casino survives with mathematics. Say, your friend invite you for a game of dice. You must bet (wager) 2 dollars. If you roll 'six' you will get back 8 dollars. The game will go on for 30 rounds. All sounds good. The probability of rolling 'six' is 1/6. Since the game will be played for 30 times, the 'expected win' is 30*1/6 = 5. That is, you are expected to win 5 rounds out of 30. Hence your gain will be 5 * 8 =40 dollars. ok. This also implies that you will loose 25 rounds. Hence your loss will be 25*2 =50 dollars. Your net gain will be gain-less = 40-50 = -10 dollars. For 30 rounds, the loss is -10 dollars, Hence, for one round =-10/30 = -1/3 dollars. There will be a loss of -1/3 or 0.33 dollars per round. It is not a fair game. Let us make a simple formula to calculate 'Pay out per round\. The probability for a win = p The pay-out in case of win = V No. of rounds = n The expect

sciencecapsules

Search This Blog