لو سمحتوا أريد بحث بالإنجليزي مكون من خمس صفحات عن الكمبيوتر ، أو الموبايل ،
أو الكتاب ، أو التعليم …..
أو أي شيء …………
بارك الله فيكم وعسى الله يجعل ما تقدمونه في ميزان حسناتكم …
اتمنى الاخوة و الاخوات يساعدونك يا عزيزة
انا والله ما عندي فكرة و ثقافتي بالانجليزي محدووووووووووودة
عفوا لكنني حدفت الموضوع الثاني لانه مثل ما بتعرفي لازم موضوع واحد في الركن
غدا ان شاء الله ارجعه
الله يوفقك اختي الكريمة
هل ينفع عن الماء مثلا؟؟؟؟؟؟؟المياة الجوفية
المهم لعل ضالتك تجدينها بين أسطري
What is ground water?
Ground water is the part of precipitation that seeps down through the soil until it reaches rock material that is saturated with water. Ground water slowly moves underground, generally at a downward angle (because of gravity), and may eventually seep into streams, lakes, and oceans.
Here is a simplified diagram showing how the ground is saturated below the water table (the purple area). The ground above the water table (the pink area) may be wet to a certain degree, but it does not stay saturated. The dirt and rock in this unsaturated zone contain air and some water and support the vegetation on the Earth. The saturated zone below the water table has water that fills the tiny spaces (pores) between rock particles and the cracks (fractures) of the rocks.
Why is there ground water?
A couple of important factors are responsible for the existence of ground water:
(1) Gravity
Nothing surprising here – gravity pulls water toward the center of the Earth. That means that water on the surface will try to seep into the ground below it.
(2) The Rocks Below Our Feet
The rock below the Earth’s surface is the bedrock . If all bedrock consisted of a dense material like solid granite, then even gravity would have a hard time pulling water downward. But Earth’s bedrock consists of many types of rock, such as sandstone, granite, and limestone. Bedrocks have varying amounts of void spaces in them where ground water accumulates. Bedrock can also become broken and fractured, creating spaces that can fill with water. And some bedrock, such as limestone, are dissolved by water — which results in large cavities that fill with water.
In many places, if you looked at a vertical cross-section of the earth you would see that rock is laid down in layers, especially in areas of sedimentary rocks . Some layers have rocks that are more porous than others, and here water moves more freely (in a horizontal manner) through the earth. Sometimes when building a road, the layers are revealed by road cuts, and water can be seen seeping out through the exposed layers.
Try as it might, gravity doesn’t pull water all the way to the center of the Earth. Deep in the bedrock there are rock layers made of dense material, such as granite, or material that water has a hard time penetrating, such as clay. These layers may be underneath the porous rock layers and, thus, act as a confining layer to retard the vertical movement of water. Since it is more difficult for the water to go any deeper, it tends to pool in the porous layers and flow in a more horizontal direction across the aquifer toward an exposed surface-water body, like a river.
Visualize it this way: get two sponges and lay one on top of the other. Pour water (precipitation) on top and it will seep through the top sponge downward into the bottom sponge. If you stopped adding water, the top sponge would dry up and, as the water dripped out of the bottom sponge, it would dry up too. Now, put a piece of plastic wrap between the sponges, creating your "confining layer" (making the bottom sponge an impermeable rock layer that is too dense to allow water to flow through it). Now when you pour water on the top sponge, the water will seep downward until it hits the plastic wrap. The top sponge will become saturated, and when the water hits the plastic wrap it won’t be able to seep into the second sponge. Instead, it will start flowing sideways and come out at the edges of the sponge (horizontal flow of ground water). This happens in the earth all the time — and it is an important part of the water cycle.
Information on this page is from Waller, Roger M., Ground Water and the Rural Homeowner, Pamphlet, U.S. Geological Survey, 1982
Ground water: Wells
There’s a good chance that the average Joe who had to dig a well in ancient Egypt probably did the work with his hands, a shovel, and a bucket. He would have kept digging until he reached the water table and water filled the bottom of the hole. Some wells are still dug by hand today, but more modern methods are available. It’s still a dirty job, though !
Wells are extremely important to all societies. In many places wells provide a reliable and ample supply of water for home uses, irrigation, and industries. Where surface water is scarce, such as in deserts,people couldn’t survive and thrive without ground water.
Types of wells
Digging a well by hand is becoming outdated today (would YOU want to do it?). Modern wells are more often drilled by a truck-mounted drill rig . Still, there are many ways to put in a well — here are some of the common methods.
Dug wells
Hacking at the ground with a pick and shovel is one way to dig a well. If the ground is soft and the water table is shallow,then dug wells can work. They are often lined with stones to prevent them from collapsing. They cannot be dug much deeper than the water table — just as you cannot dig a hole very deep when you are at the beach… it keeps filling up with water!
Driven wells
Driven wells are still common today. They are built by driving a small-diameter pipe into soft earth, such as sand or gravel. A screen is usually attached to the bottom of the pipe to filter out sand and other particles. Problems? They can only tap shallow water, and because the source of the water is so close to the surface, contamination from surface pollutants can occur.
Drilled wells
Most modern wells are drilled, which requires a fairly complicated and expensive drill rig. Drill rigs are often mounted on big trucks. They use rotary drill bits that chew away at the rock, percussion bits that smash the rock, or, if the ground is soft,large auger bits . Drilled wells can be drilled more than 1,000 feet deep. Often a pump is placed at the bottom to push water up to the surface.
Water Levels in Wells
Ground-water users would find life easier if the water level in the aquifer that supplied their well always stayed the same. Seasonal variations in rainfall and the occasional drought affect the "height" of the underground water level. If a well is pumped at a faster rate than the aquifer around it is recharged by precipitation or other underground flow, then water levels around the well can be lowered. The water level in a well can also be lowered if other wells near it are withdrawing too much water. When water levels drop below the levels of the pump intakes, then wells will begin to pump air – they will "go dry."
Information on this page is from Waller, Roger M., Ground Water and the Rural Homeowner, Pamphlet, U.S. Geolgoical Survey, 1982
Water is recharged to the ground-water system by percolation of water from precipitation and then flows to the stream through the ground-water system.
في ميزان حسناتك ،
وعلى طول إلى الوورد ثم لصق وتنسيق وطباعه ….
مشكوووووووووووره ….
————
أختي ( زهر النسرين ) :
من شروط المنتدى :
18. عدم كتابة أكثر من موضوعين في الركن الواحد في اليوم الواحد
يعني عادي نكتب موضوعين !!!!!!!!!!!!
اعتذر منك و من كل الاخوة و الاخوات
الغلطة مني انا ما انتبهت و كنت مفكرة انه عدد المواضيع يجب ان لا يزيد عن موضوع في الركن الواحد..
سنقوم بارجاع الموضوع اليوم
و ارجو ان تقبلي اعتذاري انت و الاخوات ..
الله يحفظك
وماحصل إلا كل خير ….
ونحن تحت الخدمة لتقديم أي مساعدة إن كانت بإستطاعتنا
وفقك الله 
يعني وضحي وحاضرين وتحت امرررررررررررك
الوووووونيس
أنا ممكن أساعدك في موضوعك .. لأني في نفس الوقت أكتب موضوع عن التلفون بالإنجليزي
اتفضلي…
Surprisingly, a telephone is one of the simplest devices you have in your house. It is so simple because the telephone connection to your house has not changed in nearly a century. If you have an antique phone from the 1920s, you could connect it to the wall jack in your house and it would work fine!
The very simplest working telephone would look like this inside:
it only contains three parts and they are all simple
A switch to connect and disconnect the phone from the network – This switch is generally called the hook switch. It connects when you lift the handset.
A speaker – This is generally a little 50-cent, 8-ohm speaker of some sort.
A microphone – In the past, telephone microphones have been as simple as carbon granules compressed between two thin metal plates. Sound waves from your voice compress and decompress the granules, changing the resistance of the granules and modulating the current flowing through the microphone.
That’s it! You can dial this simple phone by rapidly tapping the hook switch — all telephone switches still recognize "pulse dialing." If you pick the phone up and rapidly tap the switch hook four times, the phone company’s switch will understand that you have dialed a "4."
A Real Telephone
The only problem with the phone shown on the previous page is that when you talk, you will hear your voice through the speaker. Most people find that annoying, so any "real" phone contains a device called a duplex coil or something functionally equivalent to block the sound of your own voice from reaching your ear. A modern telephone also includes a bell so it can ring and a touch-tone keypad and frequency generator. A "real" phone looks like this:
The Telephone Network: Digitizing and Delivering
The concentrator digitizes your voice at a sample rate of 8,000 samples per second and 8-bit resolution (see How Analog and Digital Recording Works for information on digitizing sounds). It then combines your voice with dozens of others and sends them all down a single wire (usually a coax cable or a fiber-optic cable) to the phone company office. Either way, your line connects into a line card at the switch so you can hear the dial tone when you pick up your phone.
If you are calling someone connected to the same office, then the switch simply creates a loop between your phone and the phone of the person you called. If it’s a long-distance call, then your voice is digitized and combined with millions of other voices on the long-distance network. Your voice normally travels over a fiber-optic line to the office of the receiving party, but it may also be transmitted by satellite or by microwave towers. (See How does a long-distance call work? for a more detailed description.)
Not only is a telephone a simple device, but the connection between you and the phone company is even simpler. In fact, you can easily create your own intercom system using two telephones, a 9-volt battery (or some other simple power supply) and a 300-ohm resistor that you can get for a dollar at Radio Shack. You can wire it up like this:
Your connection to the phone company consists of two copper wires. Usually they are red and green. The green wire is common, and the red wire supplies your phone with 6 to 12 volts DC at about 30 milliamps. If you think about a simple carbon granule microphone, all it is doing is modulating that current (letting more or less current through depending on how the sound waves compress and relax the granules), and the speaker at the other end "plays" that modulated signal. That’s all there is to it!
Hand Generated!
You know the hand crank on those old-fashioned telephones? It was used to generate the ring-signal AC wave and sound the bell at the other end!
The easiest way to wire up a private intercom like this is to go to a hardware or discount store and buy a 100-foot phone cord. Cut it, strip the wires and hook in the battery and resistor as shown. (Most cheap phone cords contain only two wires, but if the one you buy happens to have four, then use the center two.) When two people pick up the phones together, they can talk to each other just fine. This sort of arrangement will work at distances of up to several miles apart.
The only thing your little intercom cannot do is ring the phone to tell the person at the other end to pick up. The "ring" signal is a 90-volt AC wave at 20 hertz (Hz). [/LEFT
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