CBSE PHYSICS Working Principle of Some Scientific Instruments
Diesel EngineIt is a low cost internal combustion engine with high efficiency. It consists of a cylinder with air-tight piston and provided with two valves. As the piston compresses the mixture of air and diesel, the temperature increases to 600°C leading to its ignition. The gases formed by ignition expand and push the piston out with a great force. It is connected with the gear which in turn is connected with the wheels which are set in motion. Finally the piston forces the inner gases out through another valve. This cycle is repeated again and again.
Davy’s Safety Lamp
It was invented by Sir Humphrey Davy to save the lives of the miners working in the mines. It consists of an ordinary lamp surrounded by a cylinder of wire gauze instead of glass chimney. The inflammable gases from the mine enter the gauze and burn inside the lamp with a blue flame. The gauze conducts the heat so well that the temperature outside and near the gauze never reaches the ignition point.
Dynamo
It is a device which transforms mechanical energy into electrical energy. The mechanical energy needed is obtained generally from a water turbine. It consists of a rectangular coil of wire called armature which rotates in a strong magnetic field created by electro magnet. As the coil rotates a current is induced in the coil.
Heart Lung Machine
This is a newly invented machine which promises a revolutionary advance in heart surgery. The patient’s circulation is temporarily exteriorised through the machinery by passing the heart which is left empty and idle, enabling the surgeon to work deliberately by direct vision without risk of severe haemorrhage. The heart lung machine, besides artificially circulating and oxygenating the patients’ blood can also cool it if hypothermia is necessary.
Lightning ConductorWhen heavily charged cloud comes over the building, it induces an opposite charge on the upper end of the pointed rod of the lightning conductor and similar kind of charge is repelled into the earth. If the cloud is positively charged, the pointed end becomes negatively charged. From the pointed ends charge begins to leak setting up an electric wind which neutralises some of the charge of the cloud, thus decreasing the potential difference. Thus lightning will not strike the building.
Periscope
It is a device used by crew in submarines to see the surface of the water. The head of the instrument is visible over the surface of water. Light from an object is twice or thrice reflected through a rectangular pipe in which mirrors are fixed and reaches the eye-piece in which the image is seen.
Radar
It is an abbreviated form of Radio, Angle, Direction and Range. It is an instrument used to detect the direction and distance of distant invisible objects. A narrow beam of high frequency radio-waves is sent in all directions from the instrument. The invisible object in the space reflects these waves back. Radar receives these waves and by the time taken by them determines the distance and direction of the invisible object.
Refrigerator
It is a machine used for keeping temperature sufficiently low so as to prevent foodstuffs from getting bad by preventing the growth of bacteria or moulds in them. In the modern refrigerations amonia is liquefied under high pressure at the bottom. The liquid rises in the upper portion, where foodstuffs are kept. There it evaporates and since evaporation produces cooling effect the temperature of the place goes down. This process goes on and foodstuffs are prevented from becoming bad.
Rocket
The underlying principle of the flight of a rocket is Newton’s Third law of Motion viz., to every action there is an equal and opposite reaction. It is a self-propelled vehicle which depends upon the force provided by a fuel carried along with it. As the fuel burns, products of combustion are forced out at terrific speed at the rear of the vehicle and reaction imparts motion to it in the forward direction. It has its own oxygen supply for burning the fuel and therefore, there is no dependence on air for combustion or propulsion.
Steam Engine
The motive power in a steam engine is provided by superheated steam. This steam under high pressure enters the cylinders at one end. It pushes the piston out and pushes in when escaping out from the other end of the cylinders. This process drives the piston back and forth. This piston is connected with the driving rods to the wheels of the engine and they are made to work.
Television
With the help of this Instrument we transmit images from one place to another. The object to be televised is illuminated strongly and then the light waves are by a curious mechanism converted into electrical impulses. The electrical impulses are converted back into light rays giving visual image.
Diesel EngineIt is a low cost internal combustion engine with high efficiency. It consists of a cylinder with air-tight piston and provided with two valves. As the piston compresses the mixture of air and diesel, the temperature increases to 600°C leading to its ignition. The gases formed by ignition expand and push the piston out with a great force. It is connected with the gear which in turn is connected with the wheels which are set in motion. Finally the piston forces the inner gases out through another valve. This cycle is repeated again and again.
Davy’s Safety Lamp
It was invented by Sir Humphrey Davy to save the lives of the miners working in the mines. It consists of an ordinary lamp surrounded by a cylinder of wire gauze instead of glass chimney. The inflammable gases from the mine enter the gauze and burn inside the lamp with a blue flame. The gauze conducts the heat so well that the temperature outside and near the gauze never reaches the ignition point.
Dynamo
It is a device which transforms mechanical energy into electrical energy. The mechanical energy needed is obtained generally from a water turbine. It consists of a rectangular coil of wire called armature which rotates in a strong magnetic field created by electro magnet. As the coil rotates a current is induced in the coil.
Heart Lung Machine
This is a newly invented machine which promises a revolutionary advance in heart surgery. The patient’s circulation is temporarily exteriorised through the machinery by passing the heart which is left empty and idle, enabling the surgeon to work deliberately by direct vision without risk of severe haemorrhage. The heart lung machine, besides artificially circulating and oxygenating the patients’ blood can also cool it if hypothermia is necessary.
Lightning ConductorWhen heavily charged cloud comes over the building, it induces an opposite charge on the upper end of the pointed rod of the lightning conductor and similar kind of charge is repelled into the earth. If the cloud is positively charged, the pointed end becomes negatively charged. From the pointed ends charge begins to leak setting up an electric wind which neutralises some of the charge of the cloud, thus decreasing the potential difference. Thus lightning will not strike the building.
Periscope
It is a device used by crew in submarines to see the surface of the water. The head of the instrument is visible over the surface of water. Light from an object is twice or thrice reflected through a rectangular pipe in which mirrors are fixed and reaches the eye-piece in which the image is seen.
Radar
It is an abbreviated form of Radio, Angle, Direction and Range. It is an instrument used to detect the direction and distance of distant invisible objects. A narrow beam of high frequency radio-waves is sent in all directions from the instrument. The invisible object in the space reflects these waves back. Radar receives these waves and by the time taken by them determines the distance and direction of the invisible object.
Refrigerator
It is a machine used for keeping temperature sufficiently low so as to prevent foodstuffs from getting bad by preventing the growth of bacteria or moulds in them. In the modern refrigerations amonia is liquefied under high pressure at the bottom. The liquid rises in the upper portion, where foodstuffs are kept. There it evaporates and since evaporation produces cooling effect the temperature of the place goes down. This process goes on and foodstuffs are prevented from becoming bad.
Rocket
The underlying principle of the flight of a rocket is Newton’s Third law of Motion viz., to every action there is an equal and opposite reaction. It is a self-propelled vehicle which depends upon the force provided by a fuel carried along with it. As the fuel burns, products of combustion are forced out at terrific speed at the rear of the vehicle and reaction imparts motion to it in the forward direction. It has its own oxygen supply for burning the fuel and therefore, there is no dependence on air for combustion or propulsion.
Steam Engine
The motive power in a steam engine is provided by superheated steam. This steam under high pressure enters the cylinders at one end. It pushes the piston out and pushes in when escaping out from the other end of the cylinders. This process drives the piston back and forth. This piston is connected with the driving rods to the wheels of the engine and they are made to work.
Television
With the help of this Instrument we transmit images from one place to another. The object to be televised is illuminated strongly and then the light waves are by a curious mechanism converted into electrical impulses. The electrical impulses are converted back into light rays giving visual image.
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