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How to ? Science And Technology Question & Answer – Part 7

Science Question and Answers Riddle Part 7

In How to know, about science and technology series we will provide you information about science and technology, We are in making part of series and every part will contain 8-10 scientific questions and answer !

HOW DOES A MICROPHONE WORK?

Sound waves make a microphone produce an electric signal. This signal goes to an amplifier and loudspeaker.

Inside the microphone, the sound waves strike a thin plate called a diaphragm. The diaphragm vibrates at the same rate as the sound waves. It is connected to a device that produces an electric signal varying in strength at the same rate as the vibrations.

In a crystal microphone, a piezoelectric crystal generates the signal by responding to pressure placed on it by the diaphragm.

HOW ARE RECORDS MADE?

Most records are first recorded on A tape and a master disc is made from the tape. Moulds called stampers are then made from the master disc. The records are produced by pressing a piece of plastic between the stampers.

The master tape has two sound tracks. Amplifiers send a signal from each track to the cutting head of a disc cutter. The head cuts a groove in the lacquer coating of a master disc by using the two signals to form the walls of the groove. A stamper is then made by electroplating the master disc and peeling away the layer of metal formed. This has ridges where the record has grooves.

HOW DOES A LOUDSPEAKER PRODUCE SOUNDS?

A loudspeaker makes the sounds A that come from record and cassette players, radio and television sets. Inside the loudspeaker is a cone of a material such as plastic. It is connected to a coil or wire and a magnet. When an electric signal is fed to the loudspeaker, the magnet makes the coil move. The cone vibrates and the sound comes out.

Large units produce deep sounds and small units give high sounds.

HOW DOES CITIZEN’S BAND RADIO WORK?

You can talk on the radio by using A the citizen’s band radio. You have a small radio set that is both a transmitter and a receiver: As you speak, the set sends out radio waves over a few kilometres. Anyone receiving your transmission can listen and then reply You then receive the radio waves that they transmit.

To prevent radio stations from interfering with each other, each one is allocated a different frequency for transmission. The frequencies are grouped in bands, each of which has a different kind of use.

HOW FAR CAN RADIO TRAVEL?

The radio waves that carry television A pictures move in a straight line from the transmitter to the aerial. They can go only as far as the distance from the transmitter to the horizon. Waves carrying radio broadcasts can move over the horizon. Some radio transmissions can travel around the world.

Low-frequency (long-wave) radio waves can travel over the horizon and pass around mountains.

High-frequency (short-wave) signals travel in straight lines, but are reflected back to Earth from the upper atmosphere. In this way, they can bounce around the world.

HOW DOES A TELEVISION CAMERA WORK?

A television camera produces an A image on a light-sensitive tube. This tube turns the light in the image into an electric signal. When the signal goes to a television set, the picture appears on the screen.

The lens of a television camera projects an image of the scene before it into the camera tube. In colour television cameras, there are three tubes that respond to the red, blue and green light in the image.

HOW DO TELEVISION PICTURES GET TO HOMES?

At the television studio, the cameras A produce electric signals. These picture signals then go to the television transmitter near your home, The transmitter turns the signals into radio waves that spread out through the air. The aerial on your set picks up the waves, and the television set turns them back into pictures.

The signals from the studio usually travel along cables called landlines to the transmitter. Television programmes can even be transmitted from satellites in space to homes.

HOW DO VACUUM FLASKS KEEP THINGS HOT?

A vacuum flask can keep drinks hot for several hours. This is because the flask stops as much heat escaping
from the drink as possible. As the drink loses very little heat, it keeps hot for a long time.

A vacuum flask is designed to prevent heat loss in several ways. The silver walls of the container inside the flask reflect heat rays back into the container. In addition, there is a vacuum between the walls of the container to stop heat flowing through the walls.

HOW DOES A PRESSURE COOKER WORK?

A Pressure cooker is like a large saucepan with a tight-fitting lid. A little water is put in the cooker with the food. When the cooker is heated, the water boils and produces steam inside the cooker. This steam makes the food cook very quickly.

The reason that food cooks quickly inside a pressure cooker is that it gets very hot, When the water boils inside the cooker, the steam that is produced cannot get out. It builds up a high pressure inside the
cooker.

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