human body muscles

Most electrical appliances have wires attached to them.
The wires carry an electric current around a complete pathway called an electric circuit.
Some appliances need more electric current than others before they will work.
The amount of electric current depends on how much electricity is flowing along the wires.
How can we measure the amount of electric current?
We could try counting the number of electrons that pass along the wire each second.
But this wouldnt be easy!
There are a huge number of electrons traveling along most electric wires.
About 3 million million million electrons flow through a flash bulb every second!

To make it easier, we measure the flow of electric current in amperes. 

The word ampere comes from the name of the French scientist Andre Ampere, who invented a way of measuring electric current.

We usually say amp instead of ampere. 

One amp is equal to about 6 million million million electrons every second. So a flashbulb would have a current of half an amp flowing through it.
Thats much easier!
Scientists use a special measuring device called an ammeter to measure the electric current.
The ammeter is connected into an electric circuit so that the electrons flowing around the circuit also flow through the ammeter.

One of the most important construction  projects in the history of mankind was the building of the Panama Canal.
The Panama Canal has influenced the development of trade across the globe.
The construction of the canal, shortened the distance between many ports on the Atlantic and Pacific oceans for about 8,000 miles (13,000 kilometers).
According to the first idea, the Panama Canal was supposed to be built by the French at the level of the sea, with depth of 30 feet (9 meters), and width at the bottom of 72 feet (22 meters).
However, the French plan was not realized and in 1904 The United States accepted the construction of the canal.
The French plan to dig a canal below the water level, from one ocean to the other, was dangerous.
In fact, if the differences between high and low tide on one side of the ocean were larger than the other, there would be major currents trough the channel.
This plan also required a lot more digging. Given these problems, it was decided to build a canal with locks, which meant that it must provide water at a higher altitude, in order to meet more parts of the channel.
This has been achieved with the erection of dams on the Chagres River.
Dams form one kind of staircase, through which the ships come into the channel. Ships are raised in some places where the water level is higher, and then descend to the other places.
Almost half of the canal passes through Lake Gatun.
Ships coming from the Atlantic are raised to the level of the lake by 92 feet (28 meters) through a series of three dams. On the other side - Pacific Ocean there is one notch 8 miles (13 kilometers) long. The ships then are being suspended 33 feet (10 meters) in the first dam and 60 feet (18 meters) through two other dams, so go down to sea level. Through the dams the ships are pulled with electric locomotives moving along the coast. Today, trough the dams even the largest ships can move.

Jaundice (Icterus) is a condition characterized by a yellowing of the skin and the whites of the eyes.
Jaundice is a symptom, not a disease in itself.
The yellow coloration is caused by an excess in the body of the bile pigment bilirubin.
Normally, bilirubin is formed by the breakdown of hemoglobin during the destruction of worn-out red blood cells. It is then excreted by the liver into the bile via the bile ducts.

What causes high bilirubin in the body?

High bilirubin can be caused by:

• Overproduction of bilirubin;
• Failure of the liver to metabolize bilirubin or to excrete it;
• Blockage of the bile ducts.

Overproduction of bilirubin may be caused by the destruction of an excessive number of red blood cells (hemolytic anemia).
The liver then can’t excrete bilirubin fast enough.
This occurs in malaria, thalassemia, and hemolytic disease of the newborn.
Jaundice may also result from various diseases that can affect the liver, such as hepatitis, cirrhosis or cancer.
If the bile ducts become blocked, bile can’t be excreted and jaundice occurs.
The ducts may be blocked by inflammation and in fection (cholangitis); a gallstone (cholelithiasis); or cancer of the pancreas or the common bile duct.
Occasionally a drug such as chlorpromazine may inhibit bilirubin excretion by the liver.

Jaundice in Babies

Mild jaundice occurs as a common and normal condition in newborn babies because at birth there is both a deficiency in the enzyme that helps to excrete bilirubin and also an increased breakdown of red blood cells.
In babies, the condition generally disappears within a few days as the enzyme is formed.
Rarely, this enzyme deficiency can also cause jaundice in adults.

Symptoms of Jaundice

Symptoms of Jaundice depend on the specific cause of the jaundice.
In many forms of the condition, bilirubin is excreted in the urine, which becomes dark brown in color.
If the excretion of bile is obstructed, stools are almost white and the digestion of fat is impaired.
If the condition has been present for some time, intense localized itching may occur due to blockage of the bile ducts.

How are the causes of jaundice diagnosed?

Diagnosis requires special blood tests, in which a physician determines whether the liver is diseased; whether the bilirubin is being correctly metabolized by the liver cells; and whether there is any abnormal breakdown of the red blood cells.
The urine is examined for bilirubin, and the feces for pale coloration (which would indicate an obstruction to bile excretion).
It Is sometimes necessary to perform a liver biopsy to examine Cells under a microscope or to examine the liver, gallbladder, and bile ducts with ultrasound to locate gallstones.

The world is getting warmer. If you enjoy warm weather, you may think this is good news—but it’s not. Some experts say that over the last hundred years, temperatures on the earth have increased by 2.7 to 10 degrees Fahrenheit (1.5 to 5.6 degrees Celsius).
The earth’s atmosphere is warming up, just as if it was trapped inside a greenhouse. This warming process is often called the greenhouse effect.

The panes of glass in a greenhouse let in light from the sun but trap it when it is released as heat. This makes the climate inside the greenhouse hot.
In a similar way, the earth’s atmosphere lets in sunlight and then traps the heat near the earth’s surface. This is the “greenhouse effect.

Why is the earth warming up?

More of the sun’s energy is reaching the earth’s atmosphere because the ozone layer is becoming thinner.
But there is another reason why the earth is warming up.
When we burn fuels like coal, oil, gas, or wood, carbon dioxide is released into the atmosphere. Plants use carbon dioxide to help make their food. So tropical rain forests take in large amounts of carbon dioxide from the atmosphere, but at the same time people are cutting down vast areas of these forests.
The earth is warmed by the sun.
Most of the heat is sent back, or radiated, into the atmosphere. Carbon dioxide in the atmosphere traps some of this heat, preventing it from escaping into space. This keeps the earth warm. But if there is too much carbon dioxide in the atmosphere, it will trap too much heat, and the earth’s atmosphere will become too hot.
As the earth’s atmosphere becomes much warmer, the ice in the Arctic and in Antarctica constantly melts. This raises the level of the seas all over the world. A rise of only a few inches could flood many coastlines. Low-lying coastal towns and cities would be endangered by floods, and so would large areas of farmland.
If the seas became warmer, the sea animals and plants would be affected. And many might not be able to survive at all. In other parts of the world, a lack of rain may mean that farmland would become too dry and dusty.
Too much carbon dioxide in the atmosphere prevents more heat than usual from escaping into space. But we still need some heat to keep us warm.