My Science School

CD-ROM’s are important tools for computer users. CD-ROM’s are discs that store words, music, and images. Encyclopedias, games, and other programs that would require greater storage capacity can fit onto one CD-ROM. CD-ROM stands for computer disc read-only memory.

When you put a CD-ROM into your computer’s drive, files are copied from the disc to the computer’s hard drive. These files tell the computer how to access all the information on the CD-ROM.

A DVD (digital video disc) is the same size as a CD-ROM but can store much more information. Unlike a CD or CD-ROM, the DVD is able to record data (information) on both the top and the bottom of the plastic disc. And it can record two layers of data on each side. A DVD player can also play CD-ROM’s.

A DVD contains layers of digital data encoded in tiny pits. In a DVD player, a lens focuses a laser beam on the desired layer. As the disc rotates, the pits and the flat areas between them reflect patterns of light to a photo detector, which changes the patterns into electrical signals. A single layer of a DVD has more pits, placed closer together, than an ordinary CD has, and so can store more data.

 

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Computers save us a lot of work—and a lot of time. The processor of the computer follows step-by-step instructions-exactly and quickly. This series of steps is called a program. A program might be thousands of steps long, but the processor can run the program in less than a second.

The program is stored in the computer's memory. It is stored as a series of 1's and 0's. This is called a digital code. Sometimes the code is stored on a CD-ROM or inside the computer on the hard drive. But the computer finds it when it needs it.

When you have finished a report, you tell the computer to print it. The computer sends the digital code to the printer. The printer has a microprocessor that changes the code into letters—so you and your teacher can read it.

Laser printers are the fastest printers. A beam of laser light makes an electrically charged image on a rotating, cylinder. The charged areas attract powdered or liquid ink called toner, onto the cylinder. The cylinder transfers the toner with the image onto the paper. The paper then passes through fuser rollers. These rollers seal the toner to the page so it doesn't smear.

 

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As electricity moves through the circuits in the computer, millions of tiny switches are turned on and off. The computer reads a code of zeros and ones. Think of the code as switches in a line. The ones are switches that are turned on, the zeros are switches that are turned off.

The code is called digital. Because it uses only two numbers in different patterns, it is also called binary code. When you type an A on the keyboard, the computer stores the A in its memory as 01000001. Each time you click the mouse, or press a key, it is changed to binary code and stored in the computer's memory.

It’s not only numbers and text — binary is used for the most complex data. From images to video frames, at the most granular level of the data, it is binary code.

For example, an image is built up of hundreds of thousands of pixels, with each pixel containing an RGB value stored in binary code.

These binary codes fill RGB and according to the intensity generated from those codes, the intensity numbers are thrown at a video driver program. That program distributes those colors to the million crystals on your screen — and an image is seen by us!

 

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Telephones have them. Most watches have them. They help make our cars safe. They make our telephones work more quickly. And space travel would be impossible without them.

They are microprocessors. They make our lives easier in many ways. A microprocessor is a type of microchip that can hold the signals needed to run electronic devices. Some microchips only store information. But if the microchip is also able to "figure things out," then it's called a microprocessor. A microprocessor works faster than your brain. And it can fit on the tip of your finger!

The surface of this tiny part is cut with grooves. Each groove is packed with thousands of tiny electrical switches. The switches are connected by thin metal wires. All the wires link together-a group called a circuit.

Microprocessors are also called integrated circuits. Equipment such as calculators made with integrated circuits are small, light, and easy to use.

When you use such equipment, bursts of electric currents speed along the circuits. These bursts are like messages. They tell the equipment what to do.

The most important part of a computer is its microchip, or integrated circuit. A microchip can fit on a fingertip. When seen under a microscope, the tiny grooves and wires look like a maze.

The first integrated circuit was made for the U.S. space program in 1959. Equipment on the spacecraft had to be very small. All electrical signals for the equipment were put on a strip of material called silicon. Later, circuits were made into tiny squares called silicon chips.

 

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Look at a picture of yourself. Now look at it from a different angle. Do you see another side of yourself in the picture? No, but if you were looking at a hologram you could walk around the picture and see the left side of your body, your back, your right side, your front, and the top of your head.

A hologram is an image that looks three dimensional-that is, it seems to have depth, height, and width. Some credit cards have holograms on them. Holograms also appear in advertisements, artwork, and jewellery.

A hologram is made with laser beams. A laser beam is a kind of coloured light. One laser beam is bounced off a mirror then off the subject and onto a special film. Another laser beam is also bounced off a mirror and onto the film. Where the two beams cross on the film, they make a tiny pattern of bright and dark stripes, a hologram.

Guiding a laser beam onto the film will produce light rays that seem to come from the original subject. The resulting three dimensional image appears to hover in space. You can look over, under, and around the subject. When a hologram is viewed with regular light or sunlight, the image appears with rainbowlike bands of colour.

To make a hologram of an object, such as this teddy bear, a laser is aimed into a mirror then at the object. Another laser is reflected off a mirror and then onto the film. The film records the hologram.

 

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Is a DVD the same thing as a CD? Although DVD's looks like CDs, they are different. A DVD works like a CD, but it can hold more information. A CD usually records only sound, but a DVD records pictures as well as sound.

Each side of a DVD can contain two layers. Each of these layers can store data. CD's have only one layer of information.

Before CD's and DVD's were invented, people used cassette tapes and videotapes. Cassette tapes record and play sounds, and videotapes record and play sounds and images.

Cassette tapes, videotapes, CD's, and DVD's can be played again and again. That's one of the reasons people like them so much.

A DVD can be played in a DVD player. A DVD player is often connected to a television set. When a DVD is played, pictures appear on the TV screen and sound comes out of speakers.

 

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Cassette tapes sound good when they are new. But after a while, they start to sound scratchy. A compact disc, or CD, produces much better sound. It is played using a special light called a laser beam. Only the beam of light touches the CD, so it stays like new.

Sound is stored on a CD in a digital (numerical) code-a string of 0's and 1's. When a CD is made a microphone turns sound vibrations into electrical signals. Then a machine changes the signals into a digital code.

This code is fed into a powerful laser. As a blank disc turns, the laser cuts billions of tiny pits that represent the digital code into the surface of the disc.

Inside a CD player is another, less powerful, laser. When the CD is played, the laser reads the position of the pits. The laser reads from the centre to the edge of the disc as the CD turns. These pulses of light are turned into electrical signals. The signals make the speakers vibrate. Then you hear the sounds.

Inside a CD player, a laser beam shines on a mirror and through a lens onto the pits on the CD. When the beam hits a pit, the light is scattered. When it hits between pits, the light is reflected straight back. A sensor reads the patterns of reflected light and turns the patterns into electrical signals. These signals are used to produce sounds.

 

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You probably don't think of a toilet as a machine. But that's what it is. You press down the flush lever, and the toilet does the work.

Most toilets have two main parts-a tank and a bowl. The tank sits on the back of the toilet bowl. Both contain water. The bottom of the tank has an opening with a plug. The plug keeps the water in the tank from flowing into the bowl. Pushing down the lever to flush the toilet lifts up the plug.

Water then rushes out of the tank. It flows into the toilet bowl through small holes all around the rim of the bowl.

The fresh water pushes the dirty water into the drainpipe. The plug closes when the tank is empty. Fresh water then flows through an inlet tube into the tank. And the tank is ready for the next flush.

 

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With a hairdryer, we don't have to wait for our hair to dry.

Inside the hairdryer, electricity travels on a pathway of wire. The electricity travels easily on most of the wire in the pathway. This is called conducting electricity. The path is open. The electrons in the wire are free to move.

But some metals resist, or slow down, the electric current flowing through the hairdryer. When the electrons slow down, they bump into one another as they move through the wire.

Then the wire heats up. The harder they bump and push, the hotter the wire gets.

When you plug in a hairdryer and turn it on, electricity travels through it. It powers a tiny fan. Then the electricity travels to coiled wire made of resistant metals. These wires heat up. The fan blows heat from these wires out through a vent. This is the hot air that dries your hair.

Inside an electric hairdryer, there is a coil of wire that heats up. The fan blows the heat out to dry your hair.

 

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Brrrrahhhh! It may sound like a roaring monster, but it's only a vacuum cleaner doing its dirty work. The noise comes from an electric motor that runs a fan. The fan helps the vacuum cleaner suck the dirt up the hose and into the bag.

When you turn on the vacuum cleaner, the fan starts. It draws air from the bottom of the vacuum cleaner up into the dust bin or bag. As the air moves up, it leaves an empty space at the bottom of the vacuum cleaner. Any empty space is called a vacuum. That's how the vacuum cleaner got its name.

A brush at the bottom of the cleaner helps loosen dirt in the rug. This brush is called a beater brush. A rubber belt connects the brush to the motor. As the motor spins, the brush spins and makes the rug vibrate. The vibration loosens the dirt. The vacuum pulls more air and dirt into the dust bin or bag.

When the dust bin gets full, it needs to be emptied. Or, when the bag gets full, it needs to be thrown away and replaced with a fresh bag.

 

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Are your favourite jeans dirty? No problem. Put them in the washer. They'll be clean and ready to wear in no time. When people washed clothes by hand, it took all day. After the clothes were washed, each item had to be twisted to wring out the water.

Today, a washing machine does all the work. First you choose the wash setting. Then you add your clothes and detergent. When you turn the machine on, the machine fills the washing basket, or drum, with water. A tiny computer chip, called a sensor shuts off the waterflow when the level is high enough.

The clothes twist or tumble about in the soapy water. When the clothes are clean, a pump drains the dirty water from the machine. Then the rinse cycle fills the drum with clean water. When the rinse water is pumped out, the timer switches the motor to a faster speed, and the drum spins very quickly. The clothes are flung against the sides of the drum. The water is forced out of the clothes and pumped down the drain. Now your clothes are ready to be tumble dried.

 

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Toast is tasty for breakfast or a snack. And with a toaster, it’s so easy to make.

First, you put a slice of bread in each toaster slot. A rack holds it in place. Then you push down the lever. The lever is connected to the rack and to a spring. The spring unwinds, but a hook holds the rack down. The heat turns on. The coils inside each slot glow orange.

The heat from the coils toasts the bread. It also heats a metal switch. The switch is made from two types of metal. One type expands from the heat. The other does not. As one half of the metal expands, the switch bends. When it bends, it moves a small bar. This bar pushes against the hook. The rack is released. The spring makes the rack and the toast pop up!

 

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Just a few minutes after you put warm food in a refrigerator, the food feels cooler. The refrigerator carries the heat from the food into the room outside.

How does a refrigerator do this? When a liquid changes to a gas it evaporates. As it evaporates, it takes heat from the things around it. Also, when a gas changes to a liquid, it condenses, and gives off heat. 

Refrigerators are cooled by a special liquid that is easily turned into a gas and then back to a liquid. First, the cool liquid is pumped to tubes inside the refrigerator, where it evaporates. As the liquid changes to a gas, it takes heat from the air inside the refrigerator. This makes the refrigerator cooler.

Then the warm gas is pumped into tubes outside the refrigerator, where it condenses. As the gas changes back to a liquid, it gives off heat. When the liquid cools, it is pumped back into the refrigerator. There it evaporates again. In and out it goes, carrying heat from the refrigerator and keeping the food cold.

Do you ever feel chilled when you get out of the bath or after swimming? This is because the water on your skin is evaporating off your body. It goes into the air where you can’t see it. As this happens, it takes heat away from your body, making you feel chilled.

Water vapour in the air sometimes clings to objects. On a hot day water vapour sticks to a cold glass of water. As more vapour sticks to the glass, it condenses, forming droplets of water on the outside of the glass.

 

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Are you hot or cold? A thermometer will take your temperature. There are many different kinds used for different purposes. Take your pick.

One type of thermometer has a thin glass tube partly filled with liquid. When the air is warm, the liquid in the tube becomes warm and rises. It rises because heat makes a liquid expand, or take up more space. The warmer it gets, the more space it needs. When the temperature drops, the liquid contracts, or takes up less space, so it moves down the tube. The liquid in many thermometers is a silver-coloured metal called mercury. Some thermometers are filled with coloured alcohol.

A digital thermometer has a metal probe. When the thermometer is turned on, a battery inside sends around an electric current. If the probe is warm, the current will move easily. If the probe is cool, the current will not move as easily. The thermometer shows a temperature reading based on how easily the current moves.

Doctors often use an IR thermometer to detect infrared rays from a person’s eardrum. The hotter you are, the more radiation the thermometer detects. The thermometer converts the amount of radiation to a temperature reading.

 Standard thermometer contains a liquid that moves up when it becomes warm. The liquid drops down when it cools. The lines indicate the temperature.

The lines and numbers on the thermometer indicate degrees. They tell you how much the temperature changed. Degrees are marked with the symbol º. The number 0 ºC is the temperature at which water freezes. This is the same temperature as 32 ºF. The letter C stands for Celsius, and the letter F stands for Fahrenheit.

 

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Inventors are men and women who make things that make our life easier.

Many inventions are simple. In 1865 in the U.S.A., S.E. Pettee invented a machine for making paper bags. And Earle Dickson invented the first ready-to-use bandage in 1920.

Some inventions take many years to develop. The great Italian artist Leonardo da Vinci made drawings of his ideas about 500 years ago. He drew an aeroplane, a parachute, and a helicopter. It was more than 300 years before any of these were made.

The American Thomas A. Edison invented the frst light bulb in 1879. But several other men worked on similar designs before Edison did.

To keep their ideas safe and prove they thought of it first, inventors apply for a patent. The patent gives the inventor the right to make his invention or sell his idea. Edison had ore patents than anyone else – he has 1,093!

 

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