Tag Archives: Electronics

What is the difference between noise isolating and noise cancelling headphones?

Noise Isolating

Consider the earphones that have earbuds in them. They block outside noise by providing a noise reducing barrier.

Noise Cancelling

Headphones that essentially listen to ambient noise and produce an opposite sound wave to blank out the unwanted sound. Fill your bathtub with water. Drop two rocks into the tub one at each end.  When the waves collide you will see a spot where the water seems calm because the waves are cancelling each other out. Noise cancelling headphones produce this negative wave by listening in to the outside noise and producing the opposite wave to cancel out the wave just like in the water.

Why do electronic devices which have gotten wet, stop working even when they are completely dry?

Water conducts electricity, so if a device gets wet, it can short out and destroy some components.  It’s like wiring every component to every other component.  Bad news: Only one component in an important pathway has to die for the device to stop working.

In addition to the damage being done on contact (i.e. creating short circuits leading to immediate or near-immediate failure); tap water and rain/flood water contain a lot of impurities. The evaporated water leaves these behind which may create a delayed onset of corrosion, which can cause poor contact between components and connectors.

Distilled water is actually safe for most printed circuit boards (at least those with sealed components) as long as it is applied and completely dried before power is given to the device.

How do solar panels work?

The awareness of the dwindling reserves of fossil fuels and the environmental hazards caused by them have made the world turn towards the conservative energy resources. And the solar energy tops the list of those viable sources.
Solar powered electronic appliances have been in use for many years. The solar energy is converted into electricity by solar panels. They are found in many places, from a small calculator to the International Space Station.
The solar panels work on the same principles of electronics that govern batteries or other energy storing devices. The basic element of a panel is silicon, the same element that was the reason for computer boom. Pure silicon is an ideal platform for the transmission of electrons. The atom of silicon has four electrons in their outer shell; that means they need four more to complete their shell. When two silicon atoms come in contact, they share their electrons to make both of their shells filled and it creates a strong bond between them, but without any charge. Since two plates of pure silicon would not generate electricity as there is no charge, the plates of solar panel are made by combining silicon with other elements that have positive or negative charge.
Various elements are used to make the panels including phosphorus and boron. If one plate is made with phosphorus and silicon, the next one is made of boron and silicon.
Phosphorus has 5 electrons in its outer shell. When it is combined with silicon, it results in a stable 8-electron configuration with an additional electron. This creates a negatively charged plate. When boron is combined with silicon, it results in a positively charged plate since boron has only 3 electrons in its outer shell. These two opposite charged plates are sandwiched together in solar panels, with conducive wires running between them.
The sun emits its energy mainly in the form of a particle named photon. Photons have both particle and wave properties. When the panels are pointed towards the sunlight at a certain angle, the incoming photons collide with the silicon and phosphorus atoms in the panels. The impact from this collision renders the additional electron free. The positively charged plates attract the free electrons and electricity is formed in the panel. Since there are many atoms and electrons in a panel, the process creates a fair amount of electricity.
The major problem about solar panels is the small amount of energy when compared to the size of the panels. The collision rate of photons also affects its productivity.

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How many electrons are there in electric current?

Electric current is what it is – a continuous flow of electrons which can not be quantified unless you count them at a specific point they are passing by. An electric bulb can serve this purpose. In a 60-watt light bulb, for example, about 30,00,00,00,00,00,00,00,000 (3 followed by 18 zeros) electrons a second flow past any point in the wires to the bulb filament. However, their speed of travel is only a few centimeters every second.

Additional reading:
Electric current (Wikipedia)

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How do neon and fluorescent lights work?

Neon Light
Cool and colorful, eerily radiant, a neon tube emits a light of almost seductive elegance. But mesmerizing as their shimmer may be, neon system owe their glow to nothing more glamorous than a bit of gas and a jolt of electricity. Sealed within the glass tubing of, say, an illuminated signboard is a mixture of gases, one of which will always be neon. Left to itself, neon remains still and colorless. It is only when a current of electricity is passed through the gas that it reveals its garish talents.

When such an electrical change is applied, it stimulates electrons circling a neon atom’s nucleus. Though the suddenly excited electrons lack sufficient energy to elevate their orbits and move farther away from the nucleus. This condition lasts only an instant. Almost immediately, the electrons return to their unexcited state, emitting a burst of energy that is visible, as a brilliant orange-red application of a coating of phosphor powder to the inside of the tube will yield commensurate changes in color.

Common fluorescent lights found in homes and offices work on a very similar principle. Within the glass tube is not neon but argon and mercury vapor. An electric current introduced into the mixture makes the gases give off faint bluish light and invisible ultraviolet radiation. These emissions would be useless as a light source were it not, again, for a phosphor powder coating on the inside of the tube. This substance reacts with the wavelengths created by the gases and shifts them into the visible spectrum. So efficient is the process that a 40-watt fluorescent lamp can yield as much light as a 150-watt incandescent bulb. But it is not efficiency that makes these lighting systems so appealing. It is, instead, their endless range of hues – from soft room lighting to glinting crimsons – that earns such simple atomic reactions such universal attention.

Additional reading:
Neon lamp (Wikipedia)
Neon sign (Wikipedia)
Fluorescent lamp (Wikipedia)

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How is cold generated in a refrigerator? Why is icebox positioned on top in a fridge?

It’s a law of science that if you smear a little amount of water on skin, after a while it will evaporate and you will feel coldness on the skin. The reason why it happens is that to turn water into vapor, energy is used. Evaporating water gets this energy (heat) from the body itself. Hence, the part losing heat as energy goes cold. The same principle is applied in a refrigerator. Here, the liquid called chlorofluorocarbon (CFC) evaporates in a thin tube; that is, turns into gas. While doing so CFC absorbs the heat in the refrigerator, and thus the interior is bound get cold. The CFC gas then moves towards the tangle of tubes in the rear part of the refrigerator, where it is turned again into liquid using compressor and loses its heat to the air. This liquid again absorbs the heat in the refrigerator to turn into gas.
Now remains the position of the icebox. The answer of the question related to icebox too is very interesting. It is better to keep an ice-compartment, i.e. icebox on top, because in a refrigerator more heat is accumulated in top, hence the first squirt of cold liquid should be made there. This is why it is arranged for CFC turned into liquid with compressor to flow towards the top directly. When it is inevitable to do so and also the liquid entering the top level is super cold, then why not use it to benefit? Turning water into ice necessitates removing all natural heat off it – and it is quite natural that this can be done only using the freshly entered freezing-cold liquid CFC.
More reading:
Refrigerator (Wikipedia)
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How long did the first light bulb stay lit?

Accompanying photograph shows the first electric bulb made by Thomas Alva Edison. He had used thick cotton thread as filament in his bulb which, after burning, had partially taken the form of carbon.

The bulb gave light continuously for 48 hours 40 minutes after being switched-on on October 19, 1879. Ultimately the filament of the bulb snapped on October 21, 1879. Therefore, the latter date is considered to be the date of invention of the electric bulb.

More reading:
Incandescent light bulb (Wikipedia)

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Which gasses are used in electric bulbs? Or vacuum is left inside?

There is no vacuum in the electric bulb. On the contrary, argon gas or argon gas mixed with a little nitrogen is filled in the bulb under some pressure. Years ago there was a practice to leave vacuum inside the bulb so as to prevent the burning of tungsten filament in the temperature of 2000° Celsius inside the bulb. But at such a high temperature tungsten filament starts losing its atoms. Or, to be precise twisted strands of tungsten filament start ‘evaporating’ slowly. As the escaping particles of burnt tungsten settle on the transparent glass of the bulb, accumulating carbon becomes an obstruction to the light.

Ultimately a situation comes about in which although the bulb is lit it does not throw much light in the room. Also, continuously ‘evaporating’ filament of tungsten may not last for a long time. A well-known American chemist named Erwin Lang-Moore invented two methods in 1913 to bring an end to both these problems: (1) He twisted the strands of tungsten filament weaving them into a plait which till now were in the form of spring like coils. Plaiting made the tungsten filament more durable. (2) He replaced the practice of leaving vacuum in the bulbs with that of filling them up with nitrogen or argon. Argon is an inert gas which does not give rise to any chemical reaction and so would not affect the working of tungsten filament. At the same time the pressure of Argon gas would almost prevent ‘evaporation’ of the filament.

It is because of the above two inventions that a present day electric bulb has useful life of about 1,000 hours.

More reading:
Incandescent light bulb (Wikipedia)

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What is the technique of Earthing used in a three-pin electric plug?

When an electrical appliance of high wattage like pressing iron or microwave oven does not have any flaw or defect the current passes through two smaller pins only. No current passes through the (long) third pin and the third wire connected with it. Meanwhile one end of the wire connecting the third pin remains connected with the inner surface of the appliance. Similarly, one end of the wire from the socket is connected with electricity conducting metallic plate which is buried in the Earth. This type of permanent electric connection is commonly known as Earthing.
If a live wire in the pressing iron becomes loose and touches the inner surface then electric current starts flowing in the metallic body and if a finger touches it then one gets a powerful electric shock! Human being’s body is a good conductor of electricity, so electric current which must complete circuit by entering earth passes through the body on its way! However, if a still better conductor is provided, then it is a different matter because the current will take that more convenient medium for its flow. Such better medium for the current to pass through is copper wire connected with the third pin.
There is a reason behind making this pin somewhat larger. As soon as the lower two pins enter the socket current starts flowing to the appliance and if there is some flaw or defect one may get electric shock there and then. But as the third pin is longer, before the current starts flowing to the appliance through the lower pins it is already earthed.
Additional reading:

How does compact disc (CD) work?

Having thickness of mere 1.2 millimeters and diameter of 12 centimeters CD weighs only 28 grams but has capacity to store 74 minute of music recording or 783 megabytes data on its 5 kilometers long spiral track. Compact disc mainly comprises of three layers. The topmost layer is made of acrylic, followed by aluminum and the bottom layer of polycarbonate. This bottom layer is transparent, passing through which the laser beam ‘reads’ 0.5 micron broad pits recorded on the aluminum layer. These pits are actually indicative of binary digits 0s and 1s and each 0 and 1 in turn is indicative of the connected data (viz. audio, video).
When CD is inserted in the disc drive following sequence of events takes place: Laser beam strikes the aluminum layer of CD penetrating through the transparent polycarbonate layer and is reflected towards the photo detector situated beneath the CD. (This process takes place many times in a second.) Since the pit is not flat it does not reflect laser much whereas the flat surface reflects laser more.

Photo detector detects changes in the reflected beam and constantly passes on information to electronic circuit. It is the job of this circuit to convert the digital data into electronic signals. These are processed and decoded to form sound signals that can be amplified for reproductions on loudspeakers and visual signals that can be relayed on TV.

The experts have revolutionized the field of data storage by applying this simple principle in DVD in addition to CD. In a way, the credit for this revolution belongs to James Russell.


More reading:
Compact Disc (Wikipedia)