Showing posts with label why. Show all posts
Showing posts with label why. Show all posts
Tuesday, March 21, 2017
Why An Iron Ship Does Not Sink
Why An Iron Ship Does Not Sink
If you put a nail or a lump of iron in a vessel of water it sinks at once. A piece of wood of the same size floats. So, until fifty years or so ago, people thought all boats and ships must be built of wood, or they would sink.
Take a sheet-iron pan from the kitchen and put that on the water. It floats. It weighs just as much as the lump of iron that sinks, but the weight is spread or distributed over a larger volume of water That is all. It has been made lighter than the total amount of water it rests upon. A ship is just such a hollow vessel, whether made of iron or wood. When there is nothing in it, a ship stands high, almost on the surface of the water. As it is loaded with goods and people, it rides deeper. Load your sheet iron pan with a cargo of toys. Watch it go deeper. Dont fill it to the top. That would make it as heavy as if it were solid. Then it would sink.
If you live in a lake or sea-port town, you will find that all ships have a water-line painted plainly around the hull. This is the safety loading line. No ship owners are allowed to load a vessel so heavily that that water line sinks below the surface of the water. Air spaces must be left, to keep the ship and its cargo lighter than the water that is beneath them. In the old days overloaded wooden vessels often sank. Today, iron ships ride the ocean safely.
Source: http://chestofbooks.com/reference/The-New-Student-s-Reference-Work-Vol5/Why-An-Iron-Ship-Does-Not-Sink.html#.ViIG-fkrLIU#ixzz3ooQryes9
Available link for download
Wednesday, March 1, 2017
Why Facebook User Data Matters to Advertisers
Why Facebook User Data Matters to Advertisers
Using Facebook is more common than any other social network from around the world. There are more than 1.26 billion users on Facebook as of Q3 2013, more than 1/7 of the entire worlds population. Each day, a collective 20 billion minutes is spent by daily users browsing and surfing on Facebook. Facebook statistical data and information is extremely valuable to marketers and advertisers today, whether a brand is trying to sell products, services or even plans to share content. Understanding the most popular statistics and how Facebook affects the marketing industry can help you when planning your next advertising campaign.
The more talked about topic in the US in 2013 was the Super Bowl. Additional topics that were most popular on Facebook in 2013 included The Conjuring, ABCs Scandal, "Get Lucky" by Daft Punk, and even the book "Happy, Happy, Happy: My Life and Legacy as the Duck Commander" by Phil Robertson. Additionally, the Criminal Case game created by Pretty Simple Games was also one of the most talked about topics in the US using Facebook. Coming in on the list also included Peyton Manning, the government shutdown, Instagram and even the Harlem shake.
Understanding what is popular at all times with the use of Facebook is a way for advertisers and those involved in marketing to pinpoint the best methods of reaching any specific audience or intended demographic. The more you understand about the audience you want to reach, the easier it becomes to develop well-received advertisements that are relevant, interesting, original and well-branded to your company. The more in-tune you are with the latest impact Facebook is having on its users, the more likely you are to experience success when building an online presence using networking platforms.
User Behavior
Tracking user behavior is one of the most important factors for advertisers and those who are in charge of running and managing online promotional campaigns. The top life events in the US alone during 2013 included adding a relationship, getting married, getting engaged, traveling and even moving. The remaining top life events on Facebook in 2013 included ending a relationship, having a baby, expecting a baby, first meeting someone or losing a loved one.The more talked about topic in the US in 2013 was the Super Bowl. Additional topics that were most popular on Facebook in 2013 included The Conjuring, ABCs Scandal, "Get Lucky" by Daft Punk, and even the book "Happy, Happy, Happy: My Life and Legacy as the Duck Commander" by Phil Robertson. Additionally, the Criminal Case game created by Pretty Simple Games was also one of the most talked about topics in the US using Facebook. Coming in on the list also included Peyton Manning, the government shutdown, Instagram and even the Harlem shake.
Understanding what is popular at all times with the use of Facebook is a way for advertisers and those involved in marketing to pinpoint the best methods of reaching any specific audience or intended demographic. The more you understand about the audience you want to reach, the easier it becomes to develop well-received advertisements that are relevant, interesting, original and well-branded to your company. The more in-tune you are with the latest impact Facebook is having on its users, the more likely you are to experience success when building an online presence using networking platforms.
Source: www.topmarketingschools.net
Available link for download
Tuesday, February 14, 2017
Why are DC high voltage transmission lines replacing AC high voltage transmission lines at some places
Why are DC high voltage transmission lines replacing AC high voltage transmission lines at some places
With AC systems the peak voltage is 2^0.5 (1.4142) times the RMS (nominal) voltage. At transmission voltages that additional .4142 x voltage makes the insulation systems much more critical, lengthening the insulator strings and so increasing the cost of the insulators and poles required to separate the lines.
With DC systems the peak voltage is the nominal voltage, so the insulator strings need only deal with the nominal voltage reducing capital and maintenance costs (washing from helicopters etc.).
With very high voltage transmission where maximum voltage is limited by available technology, this fact is used to increase the nominal voltage on a given insulation type, resulting in a system which would be operated at 750,000 volts nominal (RMS) AC being used for 1,000,000 volts actual DC with 25% additional capacity for the same amperage (cable) design.
The other factors are
With DC systems the peak voltage is the nominal voltage, so the insulator strings need only deal with the nominal voltage reducing capital and maintenance costs (washing from helicopters etc.).
With very high voltage transmission where maximum voltage is limited by available technology, this fact is used to increase the nominal voltage on a given insulation type, resulting in a system which would be operated at 750,000 volts nominal (RMS) AC being used for 1,000,000 volts actual DC with 25% additional capacity for the same amperage (cable) design.
The other factors are
- In HVDC no corona loss is there as incase of HVAC.
- For longer distance,HVDC system is very economical as compared to the HVAC system.
- Allowing power transmission between unsynchronized AC distribution systems.
- HVDC increases the capacity of an existing power grid in situations where additional wires are difficult or expensive to install.
- For DC frequency is 0.Therefor there is no inductive reactance drop, result of it is improve voltage regulation.
- There is no problem of stability as in AC.
- There is no skin effect in DC.
- AC require 3 wire for transmission but DC require only 2 .
- There is no ferranti effect in DC{it doesnt mean that capacitance is absent in DC,capacitance act as open CKT for DC}
Available link for download
Monday, January 23, 2017
Why laptop runs hot and turns off or freezes
Why laptop runs hot and turns off or freezes
Why laptop runs hot and turns off or freezes?
My laptop runs very hot and eventually turns off or freezes – this is one of the most common complaints I have been receiving from my customer for many years. Why it’s happening? Is there an easy fix for that?
Most likely this problem is heat related. Take a look at the following picture.
Any laptop has a cooling module which consists of heatsink and cooling fan. When laptop is working, the processor (CPU) heats up and because of that the heatsink is getting hot too. At some temperature level, the fan kicks in and cools down the heatsink.
The problem starts when the laptop cooling module collects too much dust inside. Usually dust collects between the fan and heatsink. Dust clogs the heatsink and kills normal airflow inside the cooling module. Eventually, the processor gets very hot and the laptop turns off unexpectedly or freezes. This problem can be fixed by cleaning the laptop cooling module.
Cleaning laptop cooling module.
Some laptops give you an easy access to the heatsink and fan. In laptops like that you can access the cooling module through the bottom cover.
In my example I had to remove the cooling module. Otherwise, I wouldn’t be able to remove the fan and access the heatsink. In some laptops you can remove the fan without separating the heatsink from the CPU.
After I removed the fan, I found a thick layer of dust inside the heatsink. Cleaning the heatsink should fix any heat related problems.
Apply thermal paste on the processor.
If thermal paste on the processor dried out, you should replace it with fresh thermal paste.
Remove old thermal paste from the processor and heatsink using alcohol swab.
WARNING: In some laptops the heatsink also covers the graphics chip. The part of the heatsink which covers the graphics chip might have thermal pad on it instead of regular thermal paste. Do not replace thermal pad with thermal paste! Do not apply thermal paste on the thermal pad! Just leave thermal pad alone and apply thermal paste only on the processor.
I usually use Shin-Etsu thermal paste which is relatively cheap and performs well.
What if cooling module cannot be accessed easily?
In some laptops the cooling module is buried deep inside the case and cannot be easily accessed and removed. In order to remove the cooling module it’s necessary to disassemble the whole laptop but it’s only for experienced users.
Blow air into the fan grill on the bottom of the laptop.
2. Blow air into the grill on the side of the laptop.
Switch direction a few times until all dust is gone. Most likely this quick cleaning will fix your laptop overheating problem.
Any Kind of Lenovo Problems Call Us
+1-855-517-2433 (Toll Free)
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Thursday, January 19, 2017
Why Ocean Water is Salty
Why Ocean Water is Salty
There is no salt in fresh rain-water. River water tastes fresh, sea water salty. Yet the oceans are fed by the rivers that flow into them. Then where does the salt in the sea come from?
When rain falls on the ground it soaks into the earth. In the earth are all sorts of minerals—salt, lime, magnesia, potash, sulphur, iron and many others. These are dissolved or melted and carried along by the water. Of all the minerals in the earth salt is most easily dissolved by water. So very often, we have salt springs. Rivers are fed by springs, and all of the minerals are in river water, but not enough so you can taste them. All the time this salt and other minerals are poured into the ocean by the rivers. When the sun takes vapor up into the rain clouds it takes only the water, leaving the minerals behind, just as lime is left in a teakettle. In this way the minerals in the sea, salt and everything else, slowly becomes greater in quantity as the centuries go by. About three and a half per cent of sea water is minerals, today. That is, if you put one hundred quarts of sea water in a tank and boil until the water is all boiled away, you will have three and a half quarts of dry salt, magnesia, lime, potash and other minerals. The greater part would be salt.
What would you think, then,, of water in which there are from fifteen to twenty quarts of salt and other minerals in every hundred quarts of water? The water of our Great Salt Lake and of the Dead Sea is four or five times as salt as the ocean. Like the ocean, they have no outlets in rivers. So they keep all the minerals that come into them. After ages and ages they will lose all their water, dry up and leave great salt beds behind. Do you think that could ever happen to the big oceans?
Source: http://chestofbooks.com/reference/The-New-Student-s-Reference-Work-Vol5/Why-Is-The-Water-Of-The-Ocean-Salt.html#.ViIKU_krLIU#ixzz3ooTIG3AH
Available link for download
Saturday, January 14, 2017
Carbon a Nonmetal ! But why it is used in Dc motor brushes
Carbon a Nonmetal ! But why it is used in Dc motor brushes
One reason is the high melting temperature of carbon.
The inductances of the energized windings, and the mechanics of a brush type motor or generator make arcing and sparking an unavoidable characteristic of the machine at the brush interface. Electrical arcs produce very high temperatures. High enough to melt metals.
Carbon has a very high melting point (~3500degC) compared with other conductors. Brushes made with copper or steel would wear out faster because of factors including:
1) The melted metal will break away from, or even be vaporized, leaving the brush with less material to do its job.
2) If the melted material doesnt vaporize or otherwise move away from the interface, it creates a mess for the brush. It can weld together bristles of the brush. It can build up material that interferes with the motion of the rotor.
3) As the metal melts in the presence of an arc, conductive material can be liberated, therby prolonging the arc, exasperating the wearing action.
Carbon is less prone to those high temperature effects and associated impacts to the generator operation.
Source : Dan Church
Available link for download
Why Boiling point is low in Mountain Top
Why Boiling point is low in Mountain Top
If you boil water over a camp fire on the sea shore, you have to heat it to two hundred and twelve degrees. But on a mountain top, water boils before it gets as hot as that. This is because, on low ground, there is more air above the water than on land a mile or two higher. The lighter the air pressure the easier it is for water to expand into gas. Therefore, it takes less heat on a high mountain to make water boil. Of course, then, boiling water away up on the Alps isnt nearly as hot as boiling water on a sea beach. In some very high places boiling water should be just about right for a warm bath, and water there would escape in gas long before it was hot enough to boil an egg.
Source : http://chestofbooks.com/reference/The-New-Student-s-Reference-Work-Vol5/Why-Does-Heat-Make-Water-Boil.html#.ViII8_krLIU#ixzz3ooSDNLH1
Available link for download
Wednesday, January 11, 2017
Why is electrical power transmitted at low frequencies and not at high frequencies
Why is electrical power transmitted at low frequencies and not at high frequencies
GENERATION
and the frequency is given by :
f= P*N /120
Now to produce voltage at a high frequency , two things have to be increased :
Since the number of poles in this Alternator have increased (compared to two pole High speed turbogenerators rotating at 3000/3600 RPM at 50/60 Hz respectively) , the diameter of the machine will increase which will make the size of machine large.
Now that to produce power at High frequency , you would have to rotate the machine at high speeds which would require higher steam input for same amount of power at a higher frequency.
Higher input to alternator will deteriorate it mechanically. To paraphrase a high frequency alternator needs to be mechanically robust and thus will require a larger size and more material in construction.
TRANSMISSION
While C and G are shunt parameters of line *G being frequency independent*
If the voltage at high frequency is used to transmit power
DISTRIBUTION & UTILIZATION
Even in distribution , the high frequency AC will not be that efficient :
- Power is generated from Synchronous machines (Alternators) which rotate at a particular speed called the synchronous speed given by
and the frequency is given by :
f= P*N /120
Now to produce voltage at a high frequency , two things have to be increased :
- Number of poles in machine
- Speed of machine
Since the number of poles in this Alternator have increased (compared to two pole High speed turbogenerators rotating at 3000/3600 RPM at 50/60 Hz respectively) , the diameter of the machine will increase which will make the size of machine large.
Now that to produce power at High frequency , you would have to rotate the machine at high speeds which would require higher steam input for same amount of power at a higher frequency.
Higher input to alternator will deteriorate it mechanically. To paraphrase a high frequency alternator needs to be mechanically robust and thus will require a larger size and more material in construction.
TRANSMISSION
- Coming to your actual questions about transmission of power at high frequency , We need to realize the model of transmission line
While C and G are shunt parameters of line *G being frequency independent*
If the voltage at high frequency is used to transmit power
- Drop across inductor will increase as V = I*X =I*2*3.14*f*L (f being the frequency).
- A higher drop will cause the line voltage to sag.Hence the coveted flat voltage profile will not be obtained.
- The voltage will decrease with increase in length and it will be less most at the receiving end (where it is needed the most).
- Corona loss is directly proportional to frequency, hence the losses due to corona will increase
- This will cause more interference with communication/telephone lines.
- High losses in transmission wires due to skin effect.
- Because of skin effect , the cost of conductor material will increase as the conductor is not utilized fully at high frequencies.
- Economy of transmission is a major point while designing transmission lines . increasing the cost of conductor will make the system uneconomical
- Since the resistance due to skin effect increases ( assume Rac=1.6Rdc), line losses (I^2R ones) will increase and hence the power transmission capability will decrease
- FACTS devices or compensators will be required for reactive power demand/supply making the system even more costly.
DISTRIBUTION & UTILIZATION
Even in distribution , the high frequency AC will not be that efficient :
- We use a lot of power electronic devices. A high frequency will cause large switching losses.
- Harmonics of higher frequencies being fed back to grid , filter requirements might be there.
- Poor voltage regulation
- Possibility of thermal noise/shot noise /white noise (high frequency ) interference with home appliances
Available link for download
Monday, January 9, 2017
Why we use Zero Ohm Resister
Why we use Zero Ohm Resister
In a mixed signal system its recommended to join AGND and DGND close to the mixed-signal IC, often the one performing the A-D function. The reason for this is to reduce differential noise in the mixed-signal IC. See the diagram below. The objective of minimising noise coupling from B to A is aided by joining the GNDs on a low-impedance ground plane. In a system with both an AGND plane and a DGND plane it is common to connect both the planes at this point with a link to minimise differential voltages. Sometimes this link is a wire with a ferrite bead, sometimes its a zero-ohm resistor or even just a narrow PCB trace.
See a good description here.
As for the Zero Ohm resistor. Think of it as a link that is easily placed by a pick and place machine during manufacture and also easily removable for experimentation on prototypes, if required. Because its a physical component, the ground plane connection is easily identifiable in PCB design tools which makes it easier for the designer and layout engineers to communicate intent.
Available link for download
Monday, January 2, 2017
Why 95 P C B s are of green colour
Why 95 P C B s are of green colour
Why 95% P.C.B.s are of green colour?
Answer: If the PCB itself is green, that indicates, that its made from glass-epoxy which is naturally green. Also your PCB could be made in every single color that exist. The finishing color is usually a solder mask. This mask is applied for safety reasons, for preventing eventual short circuits and etc. It could be every color, depends on the clients specifications.
Available link for download
Tuesday, December 6, 2016
Why do we use a diac for triggering a triac
Why do we use a diac for triggering a triac
Why do we use a diac for triggering a triac?
Available link for download
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