Science Facts

THE SECRET OF SUCCESS IS ????????????

2014-06-05T09:58:00.001-07:00

Once a person asked Socrates, an ancient Greek philosopher, what is the the secret of Success. Socrates thought for a moment and then told the young man to meet him near the river the next morning.

They met next morning. Socrates told the young man to walk with him inside the river.

When the water got up to their necks, Socrates took the young man by surprise and ducked him into the water. The man struggled to get out but Socrates was strong and kept him under water until he started turning blue.

The young man struggled hard and finally managed to get up. The first thing he did was to gasp and take a deep breath.

Socrates asked, “What did you want the most when you were under the water?”

The man replied “Air”.

Socrates said: “That’s the most secret to success. When you want success as badly as you want air, you will get it. There is no other secret”.

Moral of the story:

A burning desire is the starting point of all accomplishments. Just like a small fire cannot give much heat, a weak desire cannot produce great results.

How Radio Works

2012-06-28T09:31:00.004-07:00

Introduction:

Technically, radio is a small part of the electromagnetic spectrum , so-called because electromagnetic waves are driven across space at the speed of light by electric and magnetic forces. Gamma rays, x-rays, ultra-violet, visible light and infra-red are also parts of the same spectrum. They all travel at the identical speed but have different properties and uses, depending on their frequency or wavelength .

If equipment generating radio frequency energy (a transmitter) is connected to an antenna (or aerial) the energy is radiated in the form of radio waves. Some of the radiated energy can then be collected by another antenna which, when coupled to a radio receiver, enables a link to be made between the transmitter and receiver. Adding information to the radio carrier wave enables messages to be transmitted. These messages may take the form of television program-mes, voice messages, data or other forms of radio communication. Radio is an immensely versatile medium.

The way in which radio waves propagate or travel through the atmosphere varies with the frequency or wavelength of the radio signal. In general, the lower the frequency the further the distance that radio waves will travel. As the frequency increases, the waves may be obstructed or deflected by hills and buildings. At extremely high frequencies, rainfall and other weather conditions can significantly limit the effective operating range of radio communications. These propagation characteristics mean that different bands of frequencies are suited to particular types of radio use. For example, for national and international broadcasting the long-wave (approximately 148-283 kHz) and medium-wave (approximately 526-1606 kHz) bands are used. At the higher frequencies such as VHF (Very High Frequency - 30 to 300 MHz) and UHF (Ultra High Frequency - 300 to 3000 MHz), where the effective transmission range is shorter, the bands are more suited to local broadcasting or local coverage for mobile radio systems. At higher frequencies it is possible to allocate wider channels (i.e., more bandwidth) and this allows more information to be transmitted per channel than at lower frequencies. For example, at VHF, because of the greater bandwidth available, high quality stereo music can be transmitted, but a typical channel in the long wave bands will support only a low quality music broadcast.

Basic radio block diagram:

The power supply (not shown) is connected to the pre-amplifier and power amplifier blocks.

Microphone - a transducer which converts sound to voltage.
Pre-Amplifier - amplifies the small audio signal (voltage) from the microphone.
Tone and Volume Controls - adjust the nature of the audio signal.
The tone control adjusts the balance of high and low frequencies.
The volume control adjusts the strength of the signal.
Power Amplifier - increases the strength (power) of the audio signal.
Loudspeaker - a transducer which converts the audio signal to sound.

Radio Receiver System

The power supply (not shown) is connected to the audio amplifier block.

Aerial - picks up radio signals from many stations.
Tuner - selects the signal from just one radio station.
Detector - extracts the audio signal carried by the radio signal.
Audio Amplifier - increases the strength (power) of the audio signal.
This could be broken down into the blocks like the Audio Amplifier System shown above.
Loudspeaker - a transducer which converts the audio signal to sound.

Regulated Power Supply System

Transformer - steps down 230V AC mains to low voltage AC.
Rectifier - converts AC to DC, but the DC output is varying.
Smoothing - smooths the DC from varying greatly to a small ripple.
Regulator - eliminates ripple by setting DC output to a fixed voltage.

Feedback Control System

The power supply (not shown) is connected to the control circuit block.

Sensor - a transducer which converts the state of the controlled quantity to an electrical signal.
Selector (control input) - selects the desired state of the output. Usually it is a variable resistor.
Control Circuit - compares the desired state (control input) with the actual state (sensor) of the controlled quantity and sends an appropriate signal to the output transducer.
Output Transducer - converts the electrical signal to the controlled quantity.
Controlled Quantity - usually not an electrical quantity, e.g. motor speed.
Feedback Path - usually not electrical, the Sensor detects the state of the controlled quantity.

Diagrams:

Videos:

**Wish U All The Best**

How Transformer Works

2012-06-27T09:39:00.002-07:00

Introduction:

A transformer is an electrical device that takes electricity of one voltage and changes it into another voltage. You'll see transformers at the top of utility poles and even changing the voltage in a toy train set.
Basically, a transformer changes electricity from high to low voltage using two properties of electricity. In an electric circuit, there is magnetism around it. Second, whenever a magnetic field changes (by moving or by changing strength) a voltage is made. Voltage is the measure of the electric force or "pressure" that "pushes" electrons around a circuit.
If there's another wire close to an electric current that is changing strength, the current of electricity will also flow into that other wire as the magnetism changes.
A transformer takes in electricity at a higher voltage and lets it run through lots of coils wound around an iron core. Because the current is alternating, the magnetism in the core is also alternating. Also around the core is an output wire with fewer coils. The magnetism changing back and forth makes a current in the wire. Having fewer coils means less voltage. So the voltage is "stepped-down."

Transformers on the Electrical Grid

Let's look at the electricity that comes to your home. When electricity moves from a power plant it is put into a very high voltage to be able to travel long distances. The high voltage lines can be as high 155,000 to 765,000 volts to travel many hundreds of miles.
In order for your home or a store to use the electricity, it has to be at a lower voltage than on the long-distance lines. So, the electricity is "stepped-down to a lower level using a transformer. This lower voltage electricity is put into the local electric wires at a substation. The substation breaks the larger amount of power down into smaller pieces at lower voltage. It then is stepped down again and again.
Once smaller transformers take that voltage down to usually 7,200, the power leaves this substation.
In your neighborhood, a transformer on top of a utility pole, or one connected to underground wires, transforms the 7,200 volts into 220-240 volts. This is then sent into your home over three wires. The three wires go through the electric meter, which measures how much electricity you use. One of the three wires is the ground, and the other two are the positives.
Some of the electrical appliances in your home use the 220-240 volts. These are things like a water heater, stove and oven, or air conditioner. They have very special connections and plugs. Other devices, like your TV or computer only use one-half of the electricity -- 110-120 volts.
In a toy train set, the voltage is reduced even more from 110-120 and is changed from alternating current into direct current.
Some businesses use higher voltage power to run big machines. So, they don't need to have the voltage reduced as much.

Step-up and step-down transformers:

So far, we've observed simulations of transformers where the primary and secondary windings were of identical inductance, giving approximately equal voltage and current levels in both circuits. Equality of voltage and current between the primary and secondary sides of a transformer, however, is not the norm for all transformers. If the inductances of the two windings are not equal, something interesting happens.

Notice how the secondary voltage is approximately ten times less than the primary voltage (0.9962 volts compared to 10 volts), while the secondary current is approximately ten times greater (0.9962 mA compared to 0.09975 mA). What we have here is a device that steps voltagedown by a factor of ten and current up by a factor of ten:

Turns ratio of 10:1 yields 10:1 primary:secondary voltage ratio and 1:10 primary:secondary current ratio.

This is a very useful device, indeed. With it, we can easily multiply or divide voltage and current in AC circuits. Indeed, the transformer has made long-distance transmission of electric power a practical reality, as AC voltage can be “stepped up” and current “stepped down” for reduced wire resistance power losses along power lines connecting generating stations with loads. At either end (both the generator and at the loads), voltage levels are reduced by transformers for safer operation and less expensive equipment. A transformer that increases voltage from primary to secondary (more secondary winding turns than primary winding turns) is called a step-up transformer. Conversely, a transformer designed to do just the opposite is called a step-down transformer.
Let's re-examine a photograph shown in the previous section:

Transformer cross-section showing primary and secondary windings is a few inches tall (approximately 10 cm).

This is a step-down transformer, as evidenced by the high turn count of the primary winding and the low turn count of the secondary. As a step-down unit, this transformer converts high-voltage, low-current power into low-voltage, high-current power. The larger-gauge wire used in the secondary winding is necessary due to the increase in current. The primary winding, which doesn't have to conduct as much current, may be made of smaller-gauge wire.

In case you were wondering, it is possible to operate either of these transformer types backwards (powering the secondary winding with an AC source and letting the primary winding power a load) to perform the opposite function: a step-up can function as a step-down and visa-versa. However, as we saw in the first section of this chapter, efficient operation of a transformer requires that the individual winding inductances be engineered for specific operating ranges of voltage and current, so if a transformer is to be used “backwards” like this it must be employed within the original design parameters of voltage and current for each winding, lest it prove to be inefficient (or lest it be damaged by excessive voltage or current!).

Transformers are often constructed in such a way that it is not obvious which wires lead to the primary winding and which lead to the secondary. One convention used in the electric power industry to help alleviate confusion is the use of “H” designations for the higher-voltage winding (the primary winding in a step-down unit; the secondary winding in a step-up) and “X” designations for the lower-voltage winding. Therefore, a simple power transformer will have wires labeled “H₁”, “H₂”, “X₁”, and “X₂”. There is usually significance to the numbering of the wires (H₁ versus H₂, etc.), which we'll explore a little later in this chapter.

The fact that voltage and current get “stepped” in opposite directions (one up, the other down) makes perfect sense when you recall that power is equal to voltage times current, and realize that transformers cannot produce power, only convert it. Any device that could output more power than it took in would violate the Law of Energy Conservation in physics, namely that energy cannot be created or destroyed, only converted. As with the first transformer example we looked at, power transfer efficiency is very good from the primary to the secondary sides of the device.

The practical significance of this is made more apparent when an alternative is considered: before the advent of efficient transformers, voltage/current level conversion could only be achieved through the use of motor/generator sets. A drawing of a motor/generator set reveals the basic principle involved:

Motor generator illustrates the basic principle of the transformer.

In such a machine, a motor is mechanically coupled to a generator, the generator designed to produce the desired levels of voltage and current at the rotating speed of the motor. While both motors and generators are fairly efficient devices, the use of both in this fashion compounds their inefficiencies so that the overall efficiency is in the range of 90% or less. Furthermore, because motor/generator sets obviously require moving parts, mechanical wear and balance are factors influencing both service life and performance. Transformers, on the other hand, are able to convert levels of AC voltage and current at very high efficiencies with no moving parts, making possible the widespread distribution and use of electric power we take for granted.

In all fairness it should be noted that motor/generator sets have not necessarily been obsoleted by transformers for all applications. While transformers are clearly superior over motor/generator sets for AC voltage and current level conversion, they cannot convert one frequency of AC power to another, or (by themselves) convert DC to AC or visa-versa. Motor/generator sets can do all these things with relative simplicity, albeit with the limitations of efficiency and mechanical factors already described. Motor/generator sets also have the unique property of kinetic energy storage: that is, if the motor's power supply is momentarily interrupted for any reason, its angular momentum (the inertia of that rotating mass) will maintain rotation of the generator for a short duration, thus isolating any loads powered by the generator from “glitches” in the main power system.

Looking closely at the numbers in the SPICE analysis, we should see a correspondence between the transformer's ratio and the two inductances. Notice how the primary inductor (l1) has 100 times more inductance than the secondary inductor (10000 H versus 100 H), and that the measured voltage step-down ratio was 10 to 1. The winding with more inductance will have higher voltage and less current than the other. Since the two inductors are wound around the same core material in the transformer (for the most efficient magnetic coupling between the two), the parameters affecting inductance for the two coils are equal except for the number of turns in each coil. If we take another look at our inductance formula, we see that inductance is proportional to the square of the number of coil turns:

So, it should be apparent that our two inductors in the last SPICE transformer example circuit -- with inductance ratios of 100:1 -- should have coil turn ratios of 10:1, because 10 squared equals 100. This works out to be the same ratio we found between primary and secondary voltages and currents (10:1), so we can say as a rule that the voltage and current transformation ratio is equal to the ratio of winding turns between primary and secondary.

Step-down transformer: (many turns :few turns).

The step-up/step-down effect of coil turn ratios in a transformer (Figure above) is analogous to gear tooth ratios in mechanical gear systems, transforming values of speed and torque in much the same way: (Figure below)

Torque reducing gear train steps torque down, while stepping speed up.

Step-up and step-down transformers for power distribution purposes can be gigantic in proportion to the power transformers previously shown, some units standing as tall as a home. The following photograph shows a substation transformer standing about twelve feet

Substationtransformer.

Diagrams:

Videos:

** I WISH YOU ALL THE BEST**

How LED Works

2012-06-22T09:09:00.000-07:00

Introduction:

Light emitting diodes, commonly called LEDs, are real unsung heroes in the electronics world. They do dozens of different jobs and are found in all kinds of devices. Among other things, they form numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light.

Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in asemiconductor material, and they last just as long as a standard transistor. The lifespan of an LED surpasses the short life of an incandescent bulb by thousands of hours. Tiny LEDs are already replacing the tubes that light up LCD HDTVs to make dramatically thinner televisions.

In this article, we'll examine the technology behind these ubiquitous blinkers, illuminating some cool principles of electricity and light in the process.

What is a Diode?

A diode is the simplest sort of semiconductordevice. Broadly speaking, a semiconductor is a material with a varying ability to conduct electrical current. Most semiconductors are made of a poor conductor that has had impurities (atoms of another material) added to it. The process of adding impurities is called doping.

In the case of LEDs, the conductor material is typically aluminum-gallium-arsenide (AlGaAs). In pure aluminum-gallium-arsenide, all of the atoms bond perfectly to their neighbors, leaving no free electrons (negatively charged particles) to conduct electric current. In doped material, additional atoms change the balance, either adding free electrons or creating holes where electrons can go. Either of these alterations make the material more conductive.

A semiconductor with extra electrons is called N-type material, since it has extra negatively charged particles. In N-type material, free electrons move from a negatively charged area to a positively charged area.

A semiconductor with extra holes is called P-type material, since it effectively has extra positively charged particles. Electrons can jump from hole to hole, moving from a negatively charged area to a positively charged area. As a result, the holes themselves appear to move from a positively charged area to a negatively charged area.

A diode consists of a section of N-type material bonded to a section of P-type material, with electrodes on each end. This arrangement conducts electricity in only one direction. When no voltage is applied to the diode, electrons from the N-type material fill holes from the P-type material along the junction between the layers, forming a depletion zone. In a depletion zone, the semiconductor material is returned to its original insulating state -- all of the holes are filled, so there are no free electrons or empty spaces for electrons, and charge can't flow.

To get rid of the depletion zone, you have to get electrons moving from the N-type area to the P-type area and holes moving in the reverse direction. To do this, you connect the N-type side of the diode to the negative end of a circuit and the P-type side to the positive end. The free electrons in the N-type material are repelled by the negative electrode and drawn to the positive electrode. The holes in the P-type material move the other way. When the voltage difference between the electrodes is high enough, the electrons in the depletion zone are boosted out of their holes and begin moving freely again. The depletion zone disappears, and charge moves across the diode.

If you try to run current the other way, with the P-type side connected to the negative end of the circuit and the N-type side connected to the positive end, current will not flow. The negative electrons in the N-type material are attracted to the positive electrode. The positive holes in the P-type material are attracted to the negative electrode. No current flows across the junction because the holes and the electrons are each moving in the wrong direction. The depletion zone increases.

How Can a Diode Produce Light?

Light is a form of energy that can be released by an atom. It is made up of many small particle-like packets that have energy and momentum but no mass. These particles, called photons, are the most basic units of light.

Photons are released as a result of moving electrons. In an atom, electrons move in orbitals around the nucleus. Electrons in different orbitals have different amounts of energy. Generally speaking, electrons with greater energy move in orbitals farther away from the nucleus.

For an electron to jump from a lower orbital to a higher orbital, something has to boost its energy level. Conversely, an electron releases energy when it drops from a higher orbital to a lower one. This energy is released in the form of a photon. A greater energy drop releases a higher-energy photon, which is characterized by a higher frequency. (Check out How Light Works for a full explanation.)

As we saw in the last section, free electrons moving across a diode can fall into empty holes from the P-type layer. This involves a drop from the conduction band to a lower orbital, so the electrons release energy in the form of photons. This happens in any diode, but you can only see the photons when the diode is composed of certain material. The atoms in a standard silicon diode, for example, are arranged in such a way that the electron drops a relatively short distance. As a result, the photon's frequency is so low that it is invisible to the human eye -- it is in the infrared portion of the light spectrum. This isn't necessarily a bad thing, of course: Infrared LEDs are ideal for remote controls, among other things.

Visible light-emitting diodes (VLEDs), such as the ones that light up numbers in a digital clock, are made of materials characterized by a wider gap between the conduction band and the lower orbitals. The size of the gap determines the frequency of the photon -- in other words, it determines the color of the light. While LEDs are used in everything from remote controls to the digital displays on electronics, visible LEDs are growing in popularity and use thanks to their long lifetimes and miniature size. Depending on the materials used in LEDs, they can be built to shine in infrared, ultraviolet, and all the colors of the visible spectrum in between.

Diagrams:

Videos:

** I THINK IT MAY HELP YOU**

How Tub-light Works

2012-06-20T09:56:00.000-07:00

Brief Description:

A tube light works by using the principle of fluorescence. The fluorescent tube contains two filaments, one at each end of the tube, which glow to heat up the gas contained inside the tube.

The inner surface of the tube is coated with compound of elements such as phosphorus having fluorescence. While manufacturing, the tube is filled with a small amount of a gas such as mercury vapor (for a white color), carbon dioxide (for green), neon (for red color), etc.

The power supply is delivered to the tube through starter and choke. When the supply is turned on, the two filaments glow and the contacts of the starter becomes open. This action provides a high voltage across the tube and this ionizes the warmed-up gas inside the tube. This ionized gas excites the fluorescent coating inside of the tube so that it gives out visible light.

Choke:

The choke is a current limiter. A high initial voltage is required to fire the tube, and then the current must be limited to keep the bulb from burning up.

Most ballasts nowadays are actually solid state electronic. They can run the tube at a higher frequency than the AC line making it more efficient, last longer, and correct the power factor making the load on the electrical system less.

All circuit of neon tube light is like this: L(live), inductor, first heater, starter, second heater, N(neutral) connected in series. Starter is gas glow bulb where one of electrodes is made of bi-metal, and parallel capacitor for RFI. When you switch on starter bulb is short circuited and heating current flows through series circuit. After some time (few second) gas bulb is heated enough and bi-metal electrode break the series circuit. Sudden reduce in circuit current causes induction of high voltage on inductor and so on the opposite electrodes of neon tube. Neon tube starts to glow giving the light. At the same time the starter bulb continue to glow and keep hot preventing bi-metal electrode to close again. Start of neon tube may be clean or through few attempts (flickering). Inductor limits the neon tube voltage when it glows to abt. 50V.

Starter:

Fluorescent starters are used in several types of fluorescent lights. The starter is there to help the lamp light. When voltage is applied to the fluorescent lamp, here's what happens:

The starter (which is simply a timed switch) allows current to flow through the filaments at the ends of the tube.
The current causes the starter's contacts to heat up and open, thus interrupting the flow of current. The tube lights.
Since the lighted fluorescent tube has a low resistance, the ballast now serves as a current limiter.

When you turn on a fluorescent tube, the starter is a closed switch. The filaments at the ends of the tube are heated by electricity, and they create a cloud of electrons inside the tube. The fluorescent starter is atime-delay switch that opens after a second or two. When it opens, the voltage across the tube allows a stream of electrons to flow across the tube and ionize the mercury vapor.

Without the starter, a steady stream of electrons is never created between the two filaments, and the lamp flickers. Without the ballast, the arc is a short circuit between the filaments, and this short circuit contains a lot of current. The current either vaporizes the filaments or causes the bulb to explode.

Diagrams:

Videos:

!! I HOPE THIS HELPED YOU !!

2012-04-05T01:40:00.000-07:00

HOW RADIO WAVES ARE PRODUCED

Introduction: Light Waves and the Electromagnetic Spectrum

View Animation

Light consists of electromagnetic (EM) waves. An EM wave is composed of an electric field and a magnetic field that are oscillating together. The fields are oriented perpendicular to each other, and the wave travels in a direction perpendicular to both of the fields (see image at right). These waves can also be thought of as particles called photons: massless packets of energy that travel at the speed of light. In fact, EM radiation behaves as both a particle and a wave at the same time. EM waves can be characterized by any of three properties: wavelength (λ) - the distance between two adjacent crests of the wave, frequency (f) - the number of wave oscillations per second, or the energy (E) of the individual photons in the wave. For all types of EM radiation, the simple relationships between wavelength, frequency, and energy are:

where wavelength is measured in units of length such as meters (where 1 cm = 10^-2 meters, 1 micrometer = 10^-6 meters, etc.), frequency is measured in units of Hertz (Hz), where 1 Hz = 1 wave crest per second (e.g. 1 MHz = 10⁶ Hz, 1 GHz = 10⁹ Hz); c is the speed of light, which is about 3 x 10⁸ meters per second (or 186,000 miles per second); and h is Planck's constant, which is equal to 6.63 x 10^-27 erg/s, where an erg is a unit of energy. Remarkably, all forms of EM radiation (visible light, x-rays, radio waves, etc.) travel at the speed of light, regardless of their energy. Since the energy of an EM wave is directly proportional to its frequency and inversely proportional to its wavelength, the higher the energy of the wave, the higher the frequency, and the shorter the wavelength.

The different wavelengths of EM radiation cause the radiation to react differently with different materials, such as our eyes or detectors in telescopes. The way visible light of different wavelengths interacts with our eyes gives rise to "colors", with the shorter wavelengths (about 0.0004 mm) appearing as blue light and the longer wavelengths (about 0.0007 mm) appearing as red light. Even shorter wavelengths of EM radiation (such as x-rays) can pass right through tissues in our bodies. Radiation at longer wavelengths (e.g. infrared) cannot be seen by our eyes, but can be felt as heat. Radio waves are EM waves with the longest wavelengths, from 1 mm - 100 km. The image below shows the entire electromagnetic spectrum, from shorter wavelengths to longer wavelengths.


Short wavelength High frequency High energy		Long wavelength Low frequency Low energy

Just as the EM spectrum is divided up into different regions depending on wavelength, the radio region of the EM spectrum can also be divided up into different regions or "bands". These are the bands in which astronomers use radio telescopes to observe the radio waves emitted by astronomical objects. The most common radio band names and their corresponding wavelengths/frequencies are:

*Band*	*Wavelength*	*Frequency*
P-band	90 cm	327 MHz
L-band	20 cm	1.4 GHz
C-band	6.0 cm	5.0 GHz
X-band	3.6 cm	8.5 GHz
U-band	2.0 cm	15 GHz
K-band	1.3 cm	23 GHz
Q-band	7 mm	45 GHz

Astronomers must build special telescopes and detectors in order to detect EM radiation of different wavelengths. For example, optical telescopes are designed similar to the human eye, with a lens to focus incoming light onto a detector. Since radio waves have a much longer wavelength than optical light, radio telescopes are designed much differently, although the basic principles are the same. Learn more about how radio telescopes work.

Electromagnetic radiation is emitted by charged particles such as electrons when they change speed or direction (or accelerate). In the following sections we will see how this basic concept applies to the primary astrophysical processes that emit radiation at radio wavelengths.

In general, electromagnetic radiation is emitted by one of two means, eitherthermal or non-thermal mechanisms. Thermal emission, which depends only on the temperature of the emitting object, includes blackbody radiation,free-free emission in an ionized gas, and spectral line emission. Non-thermal emission, which does not depend on the temperature of the emitting object, includes synchrotron radiation, gyrosynchrotron emission, and amplified emission from masers in space.

Thermal Emission

Blackbody Radiation

Thermal emission is perhaps the most basic form of emission for EM radiation. Any object or particle that has a temperature above absolute zero emits thermal radiation. The temperature of the object causes the atoms and molecules within the object to move around. For example, the molecules of a gas, as in a planet's atmosphere, spin around and bump into one another. When the molecules bump into each other, they change direction. A change in direction is equivalent to acceleration. As stated above, when charged particles accelerate, they emit electromagnetic radiation. So each time a molecule changes direction, it emits radiation across the spectrum, just not equally. As a result, the amount of motion within an object is directly related to its temperature.

You can explore this for yourself by placing a cast-iron pan on a stove, heating it for a few minutes, and then placing it to the side. It is hot enough to be emitting a noticeable amount of infrared radiation (or heat), which you can detect by placing your hands near it. If you were to put more heat into the iron, it would eventually emit higher and higher energy wavelengths, until it would glow on its own, emitting visible light as well as infrared radiation.

Scientists call this blackbody radiation. A blackbody is a hypothetical object that completely absorbs all of the radiation that hits it, and reflects nothing. The object reaches an equilibrium temperature and re-radiates energy in a characteristic pattern (or spectrum). The spectrum peaks at a wavelength that depends only on the object's temperature. All objects in the universe behave this way. The image at left shows blackbody spectra for objects at three different temperatures: 5000 K, 4000 K, and 3000 K. It is apparent from the image that objects at lower temperatures emit more radiation at longer wavelengths. The objects in the image emit at or near the visible range of the electromagnetic spectrum; in order for an object to emit thermal radiation at radio wavelengths, it must be much colder than these objects.

The unit of temperature that astronomers typically use is called the Kelvin, and its symbol is K (no degree symbol is used). To convert from degrees Celsius to Kelvin, add 273 to the temperature in Celsius. So, if an object has a temperature of 100° C, its temperature in Kelvin is 100+273 = 373 K. Objects that are cooler than about 1000 K emit more infrared than visible light, such as the Earth orbrown dwarfs (dim, cool objects too massive to be planets but not massive enough to be stars). Hotter objects, like stars, emit mostly optical light. Very hot objects emit mostly ultraviolet radiation, such as white dwarfs (dying stars that have burned up all of the hydrogen in their cores). The major difference in the type of energy emitted by these objects is their temperature.

The Sun and other stars are, for all intents and purposes, considered blackbody radiators. By looking at the frequency or "color" of the radiation they emit, scientists can learn about the temperature of these bodies. For example, cooler stars appear red and hotter stars appear bluish-white.

One of the most famous examples of a "perfect" blackbody is known as the Cosmic Microwave Background (CMB) radiation. This is the radiation permeating the entire Universe that was released during the Big Bang explosion and has been cooling for the last 15 billion years. Today the CMB radiation is so cold (only 2.725 K, or -270° C), that most of the radiation is emitted at radio wavelengths of a few centimeters (also called "microwave" radiation; see image at right). Astronomers were able to obtain the spectrum of the microwave background using a specially designed satellite called the Cosmic Background Explorer (COBE). The blackbody nature of the microwave background spectrum matches the predictions of the Big Bang theory extremely accurately, thus confirming the theory that the microwave background radiation was created in the Big Bang explosion. The Wilkinson Microwave Anisotropy Probe (WMAP), launched in 2001, has observed the microwave background to an even higher level of sensitivity, giving astronomers greater insights into the origin and evolution of the Universe.

Free-Free Emission

View Animation | Reset

Another form of thermal emission comes from gas which has been ionized. Atoms in the gas become ionized when their electrons become stripped or dislodged. This results in charged particles moving around in an ionized gas or "plasma", which is a fourth state of matter, after solid, liquid, and gas. As this happens, the electrons are accelerated by the charged particles, and the gas cloud emits radiation continuously. This type of radiation is called "free-free" emission or "bremsstrahlung". The image at left shows the emission of a photon when a negatively charged electron (green particle) changes direction or accelerates due to the presence of a nearby positively charged ion (red particle). Some sources of free-free emission in the radio region of the EM spectrum include ionized gas near star-forming regions or Active Galactic Nuclei (AGN).

Spectral Line Emission

View Animation | Reset

Spectral line emission involves the transition of electrons in atoms from a higher energy level to lower energy level. When this happens, a photon is emitted with the same energy as the energy difference between the two levels. The emission of this photon at a certain discrete energy shows up as a discrete "line" or wavelength in the electromagnetic spectrum.

An important spectral line that radio astronomers study is the 21-cm line of neutral hydrogen. This line is emitted by the following transition: the hydrogen atom consists of one electron orbiting one proton in the nucleus. Both the electron and the proton have a "spin". In the lowest energy state, or "ground" state, the spins of both particles are in opposite directions. When the atom becomes excited, either by absorbing a photon of energy, or by bumping into other atoms, the electron absorbs a small amount of energy, and the spin of the electron "flips," so that the spins of both particles are in the same direction. When the atom reverts back to its natural state, it loses this energy by emitting a photon with a wavelength of 21 cm, in the radio region of the electromagnetic spectrum.

Non-thermal Emission

Synchrotron Emission

Non-thermal emission does not have the characteristic signature curve of blackbody radiation. In fact, it is quite the opposite, with emission increasing at longer wavelengths.The most common form of non-thermal emission found in astrophysics is called synchrotron emission. Basically, synchrotron emission arises by the acceleration of charged particles within a magnetic field. Most commonly, the charged particles are electrons. Compared to protons, electrons have relatively little mass and are easier to accelerate and can therefore more easily respond to magnetic fields.

View Animation | Reset

As the energetic electrons encounter a magnetic field, they spiral around it rather than move across it. Since the spiral is continuously changing the direction of the electron, it is in effect accelerating, and emitting radiation. The frequency of the emission is directly related to how fast the electron is traveling. This can be related to the initial velocity of the electron, or it can be due to the strength of the magnetic field. A stronger field creates a tighter spiral and therefore greater acceleration.

For this emission to be strong enough to have any astronomical value, the electrons must be traveling at nearly the speed of light when they encounter a magnetic field; these are known as "relativistic" electrons. (Lower-speed interactions do happen, and are called cyclotron emission, but they are of considerably lower power, and are virtually non-detectable astronomically).

As the electron travels around the magnetic field, it gives up energy as it emits photons. The longer it is in the magnetic field, the more energy it loses. As a result, the electron makes a wider spiral around the magnetic field, and emits EM radiation at a longer wavelength. To maintain synchrotron radiation, a continual supply of relativistic electrons is necessary. Typically, these are supplied by very powerful energy sources such as supernova remnants, quasars, or other forms of active galactic nuclei (AGN).

It is important to note that, unlike thermal emission, synchrotron emission is polarized. As the emitting electron is viewed side-on in its spiral motion, it appears to move back-and-forth in straight lines. Its synchrotron emission has its waves aligned in more or less the same plane. At visible wavelengths this phenomenon can be viewed with polarized lenses (as in certain sunglasses, and in modern 3-D movie systems).

Masers

View Animation | Reset

Another form of non-thermal emission comes from masers. A maser, which stands for "microwave amplification by stimulated emission of radiation", is similar to a laser (which amplifies radiation at or near visible wavelengths). Masers are usually associated with molecules, and in space masers occur naturally in molecular clouds and in the envelopes of old stars. Maser action amplifies otherwise faint emission lines at a specific frequency. In some cases the luminosity from a given source in a single maser line can equal the entire energy output of the Sun from its whole spectrum.

Masers require that a group of molecules be pumped to an energized state (labeled E₂ in the diagram at right), like compressed springs ready to uncoil. When the energized molecules are exposed to a small amount of radiation at just the right frequency, they uncoil, dropping to a lower energy level (labeled E₁ in the diagram), and emit a radio photon. The process entices other nearby molecules to do the same, and an avalanche of emission ensues, resulting in the bright, monochromatic maser line. Masers rely on an external energy source, such as a nearby, hot star, to pump the molecules back into their excited state (E₂), and then the whole process starts again.

The first masers to be discovered came from the hydroxl radical (OH), silicon oxide (SiO), and water (H₂O). Other masers have been discovered from molecules such as methanol (CH₃OH), ammonia (NH₃), and formaldehyde (H₂CO).

PICTURES:

VIDEOS:

CRT

2012-04-03T10:17:00.001-07:00

CATHODE RAY TUBE

Like most scientists of that era, he inspired generations of later physicists, from Einstein to Hawking.

His better-known research proved the existence of negatively charged particles, later called electrons, and earned him a deserved Nobel Prize for physics. This research led to further experiments by Bohr and Rutherford, leading to an understanding of the structure of the atom.

WHAT IS A CATHODE RAY TUBE

Look at any glowing neon sign or any ‘old-fashioned’ television set, and you are looking at the modern descendants of the cathode ray tube.Even without consciously realizing it, most of us are already aware of what a cathode ray tube is.

Physicists in the 19th century found out that if they constructed a glass tube with wires inserted in both ends, and pumped out as much of the air as they could, an electric charge passed across the tube from the wires would create a fluorescent glow. This cathode ray also became known as an ‘electron gun’.

Later and improved cathode ray experiments found that certain types of glass produced a fluorescent glow at the positive end of the tube. William Crookes discovered that a tube coated in a fluorescing material at the positive end, would produce a focused ‘dot’ when rays from the electron gun hit it.

With more experimentation, researchers found that the ‘cathode rays’ emitted from the cathode could not move around solid objects and so traveled in straight lines, a property of waves. However, other researchers, notably Crookes, argued that the focused nature of the beam meant that they had to be particles.

Physicists knew that the ray carried a negative charge but were not sure whether the charge could be separated from the ray. They debated whether the rays were waves or particles, as they seemed to exhibit some of the properties of both. In response, J. J. Thomson constructed some elegant experiments to find a definitive and comprehensive answer about the nature of cathode rays.

THOMSON’S FIRST CATHODE RAY EXPERIMENT

Thomson had an inkling that the ‘rays’ emitted from the electron gun were inseparable from the latent charge, and decided to try and prove this by using a magnetic field.

His first experiment was to build a cathode ray tube with a metal cylinder on the end. This cylinder had two slits in it, leading to electrometers, which could measure small electric charges.

He found that by applying a magnetic field across the tube, there was no activity recorded by the electrometers and so the charge had been bent away by the magnet. This proved that the negative charge and the ray were inseparable and intertwined.

THOMSON’S CATHODE RAY SECOND EXPERIMENT

Like all great scientists, he did not stop there, and developed the second stage of the experiment, to prove that the rays carried a negative charge. To prove this hypothesis, he attempted to deflect them with an electric field.

Earlier experiments had failed to back this up, but Thomson thought that the vacuum in the tube was not good enough, and found ways to improve greatly the quality.

For this, he constructed a slightly different cathode ray tube, with a fluorescent coating at one end and a near perfect vacuum. Halfway down the tube were two electric plates, producing a positive anode and a negative cathode, which he hoped would deflect the rays.

As he expected, the rays were deflected by the electric charge, proving beyond doubt that the rays were made up of charged particles carrying a negative charge. This result was a major discovery in itself, but Thomson resolved to understand more about the nature of these particles.

THOMSON’S THIRD EXPERIMENT

The third experiment was a brilliant piece of scientific deduction and shows how a series of experiments can gradually uncover truths.

Many great scientific discoveries involve performing a series of interconnected experiments, gradually accumulating data and proving a hypothesis.

He decided to try to work out the nature of the particles. They were too small to have their mass or charge calculated directly, but he attempted to deduce this from how much the particles were bent by electrical currents, of varying strengths.

Thomson found out that the charge to mass ratio was so large that the particles either carried a huge charge, or were a thousand times smaller than a hydrogen ion. He decided upon the latter and came up with the idea that the cathode rays were made of particles that emanated from within the atoms themselves, a very bold and innovative idea.

LATER DEVELOPMENTS

Thomson came up with the initial idea for the structure of the atom, postulating that it consisted of these negatively charged particles swimming in a sea of positive charge. His pupil, Rutherford, developed the idea and came up with the theory that the atom consisted of a positively charged nucleus surrounded by orbiting tiny negative particles, which he called electrons.

Quantum physics has shown things to be a little more complex than this but all quantum physicists owe their legacy to Thomson. Although atoms were known about, as apparently indivisible elementary particles, he was the first to postulate that they had a complicated internal structure.

Thomson’s greatest gift to physics was not his experiments, but the next generation of great scientists who studied under him, including Rutherford, Oppenheimer and Aston. These great minds were inspired by him, marking him out as one of the grandfathers of modern physics.

Read more: http://www.experiment-resources.com/cathode-ray.html#ixzz1qztpIc21

WORKING OF CRT

A CRT is composed of several parts, all working together to for a coherent picture. A CRT contains a cathode, or a negative electronic terminal. It consists of a thick, heated wire that is contained within a glass tube. This tube is vacuum-sealed to eliminate resistance. The cathode emits a stream of electrons into the tube, which travel down its length and are attracted and accelerated by an anode, a positive terminal. After the electrons are sped up to extremely high speed, they strike a phosphorescent screen at the end of the tube, causing it to glow. However, it's important to note that, in addition to these parts, CRTs also require steering coils. These coils consist mainly of copper wire wrapped around the picture tube itself, and create magnetic fields that steer the electron beam to the desired pixel on the screen. These magnetic fields can be manipulated with extreme precision by changing the voltage of the wiring to focus the electron beam to any point on the screen.

Color television screens use three electron beams at once. They use one each for red, blue and green. These three colors are used in the phosphor coating on of the picture tube. When each color is struck by its respective electron beam, it glows, creating a color picture. In black and white picture sets, there is a single phospor, which glows white when struck by the beam of electron radiation emitted from the picture tube. The human eye has been trained into assembling these small dots into a cohesive picture. Obviously, the more "dots per inch" the higher the "resolution", and the clearer the picture. The highest quality pictures may consist of hundreds of thousands of "dots per inch" creating an extremely clear picture.

While CRTs certainly dominate the market now, what may happen in the future is a completely different story. Plasma televisions, once prohibitively expensive, have dropped considerably in price since their introduction. The newest possible CRT replacement are LCD televisions. They are providing a serious challenge to older CRT televisions. The advent of High Definition Television, or HDTV, has given the LCD and Plasma screens a growing sector of the market. CRT screens are limited as to the precision of the picture quality they offer, and as broadcast picture quality improves over time, CRTs may not be able to translate that picture quality onto the screen.

PICTURES:

The Braun Tube

This is one of five CRT oscilloscopes developed by Ferdinand Braun in 1897. Using a bellows, it took a strong man to evacuate the air. The successor to Sir William Crookes' vacuum tubes some 20 years earlier, these tubes used "cold" cathodes, which means they were unheated, but required a huge voltage. (Image courtesy of O'Neill's Electronic Museum)

Flat Panel Vs. CRT

The L66 was Eizo's first 18" desktop LCD display. Sitting next to its CRT counterpart, the flat panel not only took up less space, but used less energy and emitted less radiation. It was also glare proof. Formerly selling in the U.S. under the Nanao brand, Eizo is known for its high-quality monitors. (Image courtesy of EIZO Nanao Technologies Inc.)

CRT Front Projection

The first data and TV projectors used CRTs, and although mostly abandoned, they continue to provide the highest quality. In 2000, this home theater was built by a serious video enthusiast. (Images courtesy of Kal of CurtPalm.com)

CRT Rear Projection

Although big and bulky, the Pioneer Elite Pro-107 was perhaps the best CRT-based rear-projection TV ever made. Still working fine after 17 years, this unit was sold for a pittance in 2010. See rear-projection TV.

How colours are generated in television

2012-04-01T00:21:00.000-07:00

Introduction

How Colors Exist

A basic understanding of how colors are created is the first step in providing correct answers. Here are two examples:

The color of a tangible object is the result of pigments or molecular coloring agents. For example, the color of a red apple (in the illustration at the left) is the result of molecular coloring agents on the surface of the apple. Also, a painting of a red apple is the result of red pigments used to create the image.

The colors of objects viewed on a television set or on a computer monitor are the result of colored light (in the illustration at the right). If you're not familiar with how colors are created by light, look at your monitor or television screen close up. Put your eye right up against the screen. A small magnifying glass might help. This is what you will see:

A simplified way to explain it is that the color of a red apple on a computer or television is created by photons of red light that are transmitted within the electronic system.

Primary Colors

It's also important to understand the concept of "primary" colors. The fundamental rule is that there are three colors that cannot be made by mixing other colors together. These three, red, blue, and yellow, are known as the primary colors.

Now that we've described two different categories of colors (pigment and light-generated) and have a definition of primary colors, the answer to whether black and white are colors can be answered.

Color Theory 1 - Color as Light

(Additive Color Theory)

Red, Green, and Blue
(The primary colors of light)

The question:
Are black and white colors when generated as light?

Black and white cats generated on a television.
These colors are created by light.

The answers:
1. Black is the absence of color (and is therefore not a color)

Explanation:
When there is no light, everything is black. Test this out by going into a photographic dark room. There are no photons of light. In other words, there are no photons of colors.

2. White is the blending of all colors and is a color.

Explanation:
Light appears colorless or white. Sunlight is white light that is composed of all the colors of the spectrum. A rainbow is proof. You can't see the colors of sunlight except when atmospheric conditions bend the light rays and create a rainbow. You can also use a prism to demonstrate this.

Fact: The sum of all the colors of light add up to white. This is additive color theory.

When you're finished with black & white, explore some real colors at Color Matters: The Meanings of Color

Color Theory 2 - Color as Pigment or Molecular Coloring Agents

(Subtractive Color Theory)


Red, Yellow, and Blue (The primary colors of pigments in the art world)	Cyan, Magenta, and Yellow (The primary colors of inks in the printing industry) *

The question:
Are black and white colors when they exist as pigments or as molecular coloring agents?

Black and white cats created by colored crayons.
This is color generated by pigments.

Black and white cats. The colors of the fur is the result of molecules.

The answers:
1. Black is a color. (Chemists will confirm this!)

Explanation:
Here's a simple way to show how black is made: Combine all three primary colors (red yellow and blue) using a liquid paint or you even food coloring. You won't get a jet black, but the point will be clear. The history of black pigments includes charcoal, iron metals, and other chemicals as the source of black paints.
Resource: History of Pigments

Therefore, if someone argues that black is the absence of color, you can reply, “What is in a tube of black paint?” However, you must add the fact that black is a color when you are referring to the color of pigments and the coloring agents of tangible objects.

2. White is not a color.
... but .... in some cases you could say that white is a color.

The grey area:

Technically, pure white is the absence of color. In other words, you can't mix colors to create white. Therefore, white is the absence of color in the strictest sense of the definition.

However, when you examine the pigment chemistry of white, ground-up substances (such as chalk and bone) or chemicals (such as titanium and zinc) are used to create the many nuances of white in paint, chalk, crayons - and even products such as Noxema. It's worth noting that white paper is made by bleaching tree bark (paper pulp). Therefore, you could say that white is a color in the context of pigment chemistry.

More Information about CMYK primary colors:
In theory, mixing equal amounts of three primary colors should produce shades of grey or black when all three are fully saturated. In the print industry, cyan, magenta and yellow tend to produce muddy brown colors. For this reason, a fourth "primary" pigment, black, is often used in addition to the cyan, magenta, and yellow colors.

There's more to color than black and white! When you're finished with this article, discover the 3 most important things about color at Color Matters. SeeBasic Color Theory

Science Facts

THE SECRET OF SUCCESS IS ????????????

How Radio Works

Introduction:

Basic radio block diagram:

Radio Receiver System

Regulated Power Supply System

Feedback Control System

Diagrams:

Videos:

How Transformer Works

Introduction:

Transformers on the Electrical Grid

Step-up and step-down transformers:

Diagrams:

Videos:

How LED Works

Introduction:

What is a Diode?

Diagrams:

Videos:

How Tub-light Works

Brief Description:

A tube light works by using the principle of fluorescence. The fluorescent tube contains two filaments, one at each end of the tube, which glow to heat up the gas contained inside the tube.

Choke:

Starter:

Diagrams:

Videos:

!! I HOPE THIS HELPED YOU !!

HOW RADIO WAVES ARE PRODUCED

Introduction: Light Waves and the Electromagnetic Spectrum

Thermal Emission

Blackbody Radiation

Free-Free Emission

Spectral Line Emission

Non-thermal Emission

Synchrotron Emission

Masers

PICTURES:

VIDEOS:

CRT

CATHODE RAY TUBE

WHAT IS A CATHODE RAY TUBE

THOMSON’S FIRST CATHODE RAY EXPERIMENT

THOMSON’S CATHODE RAY SECOND EXPERIMENT

THOMSON’S THIRD EXPERIMENT

LATER DEVELOPMENTS

WORKING OF CRT

How the Cathode Ray Tube Works:

The Future of CRT Televisions

PICTURES:

How colours are generated in television

Introduction

Color Theory 1 - Color as Light

Color Theory 2 - Color as Pigment or Molecular Coloring Agents