Know More..

Category Modern Science

What do you know about Sound?

SOUND

One of the most familiar forms of energy in daily life is sound. We hear natural sounds like birdsong and wind. We hear the noise of vehicles and machines, and sounds such as speech and music from radios, televisions and stereo systems. We also rely on sounds to communicate when we talk to others.

Sounds are made by objects that vibrate (move to and fro rapidly). As an object vibrates, it alternately pushes and pulls at the air around it. The air is squashed and stretched as the molecules of the gases in air are pressed close together and then pulled farther apart. These are regions of high and low air pressure. They pass outwards away from the object in all directions. They are called sound waves.

Sound waves start as the energy of movement in the vibrations. This is transferred to the energy of movement in air molecules. As the sound waves spread out they widen and disperse, like the ripples on a pond after a stone is thrown in. So the sound gradually gets weaker and fades away. However if there is a hard, smooth surface in the way, such as a wall, then some sound waves bounce off it and come back again. The bouncing is known as reflection and we hear the returning sound as an echo.

Sounds also travel as vibrations through liquids, such as water, and solids, such as metals. The atoms or molecules are closer together in liquids than in air, and even closer still in solids. So sounds travel through them much faster.

            An object that vibrates to produce sound waves is a sound source. A bow rubs over the cello’s string and makes it vibrate. The vibrations pass into the air and also to the cello’s hollow body making the sound louder and richer.

The speed of sound varies depending on the substance it travels through. Atoms in steel are closer than molecules in air, so the vibrations of sound move faster and further.

Picture Credit : Google

What is Conservative Energy?

CONSERVING ENERGY

Energy can be changed or converted from one form to another. But it is never destroyed or created, lost or gained. It is conserved – the amount stays the same. At the end of a process or event, the total amount of energy is the same as at the beginning. For example, the chemical energy in a car’s petrol is converted into the same amount of energy as the car’s motion, heat and sound. The principle of energy conservation means the total amount of energy in the Universe is always the same.

Another form of energy is matter itself. Matter can be converted into energy and energy can be changed into matter. This conversion is used in nuclear power stations. A nuclear particle called a neutron smashes into the nucleus of a uranium atom (1). The nucleus breaks into two parts (2). This releases large amounts of heat and other energy and also two more fast-moving neutrons (3). These smash into more uranium nuclei and so on in a chain reaction (4). Splitting of nuclei is known as nuclear fission. During the process bits of matter cease to exist and become vast quantities of energy instead.

A similar process of changing matter into energy happens naturally in the Sun. The Sun is made mainly of hydrogen. Tremendous temperatures and pressures at its centre squeeze or fuse together the nuclei of the atoms (1) to form the nucleus of a helium atom (2).Vast amounts of energy are given off (3) which emerge from the Sun mainly as light and heat. A neutron may also be given off to continue the reaction (4). Since the nuclei join or fuse, this is called nuclear fusion. Compared to fission used in our nuclear power stations, fusion power would cause less radioactive wastes and pollution. Fusion power may be the energy source of the future.

            Geothermal energy from hot rocks deep in the Earth causes geysers, jets of hot water and steam. This form of energy will last millions of years.

Picture Credit : Google

What do you mean by Energy?

ENERGY

Energy is the ability to make things happen, cause changes and carry out work. Any change anywhere in the Universe, from a tiny meteorite hitting a planet to an exploding star, means that energy is at work. In daily life, energy is all around us in many different forms. Light and sound energy travel through the air as waves. Heat is a form known as thermal energy. Movement or motion is, too, and is called kinetic energy. Objects even have energy because of their place or position. This is called potential energy. A boulder on a hilltop has potential energy because gravity tries to pull it down. As the boulder begins to roll its potential energy changes into kinetic energy.

Energy can cause changes and it can change itself. It can convert between one form and another. The boulder rolls down the hill, converting some of its potential energy to kinetic energy. Water also flows downhill with kinetic energy. We can harness this kinetic energy in a hydro-electric power station and convert it into electrical energy, yet another form of energy. Electricity is very useful in our modern world. It can be transported long distances along wires. It can be converted to other forms of energy, like light from a light bulb, heat in an electric kettle and sound from a loudspeaker.

Matter contains chemical energy, in the links or bonds between atoms. The bonds need energy to form and they release this energy when they are broken. We make use of chemical energy in fuels such as petrol. The bonds break as the fuel burns and releases heat.

Energy from the Sun bathes our world. It is in two main forms, light and heat. It takes more than 8 minutes to travel nearly 150 million kilometres through space to Earth.

Energy is all around, present in different forms and changing from one form to another. Without energy our world would be completely dark, cold, still and silent.

The human body needs energy to drive its life processes like heartbeat, breathing and movement. The energy is present in chemical form as the nutrients in our food. We digest the food to obtain the energy and store it as body starches and sugars.

Chemical energy in the body in the form of blood sugar is taken to muscles. The muscles convert it into the energy of motion so we can move about.

Picture Credit : Google

How do trawlers fish?

               There is perhaps no human activity older, more varied or stranger, than fishing. He tricks and catches fish in different ways, such as using his bare hand, or fishing even with harpoon guns in whaling! But the method most used today is the one by which it produces the biggest share of commercial fishing known as trawling. Do you know how do trawlers fish?

               Trawlers fish with a bag-size net. It is let out on long warps or ropes. The fish are swept in at the wide, open end and then get trapped at the narrower, closed end. The trawler may be between 100 to 1500 metres long or more. In this system, the motorized fishing boats trawl by towing a large net in three different ways to keep the mouth of the net open. Firstly, a beam can be placed across the head of the net; secondly a pair of boats can be used – one at each side of the net to tow it and thirdly, some floating weights, called otter boards can be attached to the sides of the mouth of the net.

               However, the beam trawl is only used on a few small fishing crafts, and on the other hand, pair trawling is used to catch fishes from the bottom of the sea to enormous depths, sometimes at the range of 1500 metres or more. When the net is full, powered winches haul it on the board through a ramp. The otter trawl is widely used and is employed on almost every fishing technique except the smaller trawlers.

               The net gathers in everything including eggs, newly hatched fishes and algae. But this system is considered to be very destructive and alarming in the context of overfishing along the seas. Sometimes an entire fleet of fishing vessels is headed by a large factory ship fitted out just for processing of the catch. A single “sweep” of the net often taken in terms of tonnes of fish provides an idea of the quantity of fish caught in rich seas. Deep sea fishes like sardines and herrings together account for eighteen percent of the world’s catch.

               Today, the large motor fishing vessels are fitted with sonar or echo-sound equipments to locate a shoal of fish.

 

Where would a ball fall when thrown inside a running train?

               You might say that the ball would fall behind the person who throws it because he would have moved forward with the moving train. But in fact this is not correct.

               You can perform a simple experiment to answer this question. You would be surprised to find that the ball lands right in your hand when thrown upward inside the moving train. Do you know why it happens so?

               In a moving train everything inside the train also moves with the speed of the train, for example, the fans, passengers, you and the ball in your hand. When you throw up the ball, a part of the speed of the train is imparted to it. It acquires a vertical motion in addition to its horizontal motion. The passengers in the train cannot see its horizontal motion but only its upward and downward movements.

               Imagine a man outside the train, who is watching your experiment. As we have said the ball possesses both vertical and horizontal motions, both these motions combined together make the ball travel along a parabolic path. The observer outside the train will see the ball moving in a parabolic path but a passenger in the train will see only the up and down motions of the ball.

               Now the question arises whether the ball follows the parabolic path or just moves up and down? Out of these two which one is right? In fact, all motion is relative to the observer. There is nothing like absolute motion and hence the motion of the ball is different for the two observers. 

How does an Electric Bell function?

               When you push the button of an electric door bell or calling bell it keeps on ringing as long as the button remains pressed.

               Do you know how does it function? An electric bell is a simple device based on the magnetic effects of electric current. It is used in offices, houses, industries and for fire alarms.

               It consists of a U-shaped electromagnet and a soft-iron armature. The armature has a small hammer for striking the gong. This hammer hits the gong repeatedly and produces sound. The gong is made of a metal. For operating the bell, a push button is pressed. In an electric bell, the button is a switch that connects the supply of electricity to the bell.

               When the button of the bell is pressed, the current flows through electromagnet winding, armature, contact spring and the contact screw. The flow of the current magnetizes the soft-iron core of the electromagnet. This attracts the armature, causing the attached hammer to strike the metal gong and thereby produce sound.

               As the armature moves forward due to magnetic attraction the contact spring moves away from the contact screw. This breaks the circuit and the current stops flowing. As a result, the soft-iron core loses its magnetism. It, therefore, no longer attracts the armature which, then, is pulled back by the contact spring to its original position. As soon as the armature comes to its original position the electric circuit is again completed and the soft iron becomes magnetized. It again attracts the armature and thereby the hammer strikes against the gong and produces sound. As long as the push button remains pressed, the circuit is alternately broken and completed causing the hammer to strike the gong. Thus an electric bell keeps ringing.

               If a steel core is used instead of a soft-iron, then the steel core will become a permanent magnet due to passage of electric current through the winding. Consequently, the armature will stay attracted even when the contact spring moves away from the contact screw, so the hammer will strike the gong only once.

 

What is Osmosis?

               It is a well known fact that when resins are put in water they get swollen. This swelling takes place due to the entry of water through the membrane of the resins. Similarly, if grapes are put in sugar solution they shrink. Swelling of resins and shrinking of grapes take place due to a process known as osmosis. Do you know what this osmosis is?

               Osmosis is a process in which a solution of lower concentration passes into a solution of higher concentration through a semipermeable membrane. A semipermeable membrane is one that allows some, but not all, substances to pass through it. This contains very small pores. When resins are put into water, the covering acts as a semipermeable membrane. Water is less concentrated than the substance present inside the resins and so the water moves into the resins through its semipermeable membrane. Similarly, fluid from grapes moves out through the semipermeable membrane, as the concentration of sugar solution is more than that of the grapes. There is a tendency for solutions separated by a membrane to become equal in molecular concentration.

               In osmosis, the movement is always from a dilute solution into a solution of higher concentration. This reduces the concentration of the stronger solution. The rate of osmosis depends upon the comparative strengths of the two solutions. The greater the difference, the faster the rate of osmosis. This process continues until both solutions are of equal strength. When this equilibrium is reached, osmosis stops.

               Osmosis is an ongoing process among the living beings. The membranes of cells are semipermeable. Plants absorb water and dissolved minerals from the soil by osmosis; they use osmosis to move the water and dissolved minerals through the plant, cell by cell. Osmosis also maintains turgor pressure. Turgor pressure is the pressure of water on the cell. It gives the cell form and strength. When there is a decrease in turgor pressure, the plant will soon wilt and lose its regular stiffness.

               Osmosis allows the transfer of water and dissolved nutrients in the human body from the blood into the cells.

 

How do electrically heated appliances work?

Electric heaters, immersion heaters, electric irons, electric kettles, etc. are appliances which produce heat through electricity. All these appliances are based on the heating effects of electric current. When electric current is passed through a wire, it gets heated up. Heating of a wire depends upon two facts: first, on the resistance of the wire and then on the amount of electric current passed. The heat produced in the wire is directly proportional to the resistance of the wire and that of the square of the current. The amount of heat produced also depends upon the time for which the current passes through the wire.

Based upon this property of current, many domestic electric appliances have been developed. The working principle of all these appliances is almost the same, the difference lies only in their construction. An electric heater consists of a coil of nichrome wire which is in the form of a spring. This coil is mounted on an insulating base plate made of clay. When electric current is passed through the coil, it gets heated up. Room heaters are also made in a similar way, the only difference being that nichrome wire is wound around an insulating rod and a reflector is mounted at the back of the coil which reflects the heat radiation.

Immersion heaters also consist of a nichrome wire which is enclosed in a metal tube. To isolate the wire from the metal tube, an insulating powder is filled in the tube. This powder acts as an insulator for electricity but conducts heat. When the two terminals of the wire are connected to an electric source, the current starts flowing through the wire and it gets heated up. The immersion heater is put inside a bucket full of water to heat the water.

An electric iron is used to remove the wrinkles from washed clothes. This appliance also consists of a ribbon of nichrome wire which is enclosed between two sheets of mica. This spreads the heat uniformally along the base plate of an electric iron. Mica sheets are mounted on a heavy metal plate. This metal plate, when pressed against the surface of the cloth, removes the wrinkles from the cloth.

Electric irons are of two types: automatic and manual. Automatic one is fitted with a thermostat control which regulates the temperature. Manual irons do not have such a device. When the iron is cold, thermostat provides and maintains a constant temperature by the use of a device that cuts off the supply of heat when the required temperature is exceeded.

An electric kettle is used to prepare tea or coffee. It also consists of a heating element fitted at the bottom of the vessel and is isolated from it. Water is put into the vessel which gets heated when current is passed through the heating element.

For all electrically heated appliances, it is very essential to have an earth connection. Immersion heaters should not be switched on, until there is water in the bucket. The electric bulb is also a similar device whose filament gets heated up when the electric current is passed through it and it produces light.

 

How do a mixer and grinder work?

               Mixer and grinder are very useful domestic appliances. With the help of these appliances we can grate, grind and prepare mango shake, milk shake, cold coffee etc. in a short period of time. Butter can be extracted from cream by using this apparatus. Pulses and spices can also be ground easily with its help.

               This apparatus consists mainly of two parts. One is the base of the apparatus which is fitted with a high speed motor. This motor makes 15-20 thousand revolutions per minute. It also consists of a variable switch by which the speed of the motor can be adjusted with the other part of the apparatus known as a mixer and grinder. This is usually made of stainless steel or plastic in the shape of a jar. It is fitted with blades which revolve with the speed of the motor. This rotating blade minces the food material into small pieces.

               Modern mixer and grinders also consist of other attachments such as a juicer with the help of which we can extract the juices of apples, oranges, tomatoes and other fruits and vegetables. In this attachment juice pours out on one side and pulp from the other side. Most modern grinders and mixers can be fitted with various other attachments such as a slice grater, meat mincer, dough maker etc. Nowadays we have grinders by which even wheat or maize can be ground.

               These electrically operated machines have minimized the tedious work in a kitchen. Not only do these machines save time but also provide neat, clean and tasty food for us. Moreover, these machines do not consume much electricity.

What is a Robot?

          A robot is an automatic machine which can work like a human being. It can replace man in various branches of scientific and industrial tasks because it does not suffer from human limitations. It may or may not resemble a human being but definitely can work like a human being. The robots which resemble humans are called androids.

          The word ‘robot’ was first used in the play ‘Rossum’s Universal Robots’ by the Czechoslovak dramatist, Karel Capek, who had derived it from a Czech, word ‘Robota’ which means a forced or bonded labourer.

          The industrial revolution and automations stimulated the invention of robotic devices to perform certain human tasks. A human worker, however superb a craftsman he may be has certain limitations. He cannot work continuously in a hostile environment. He cannot work for long periods because he gets tired. He may be in short supply and may be expensive to hire. Modern industrial robotic devices aim to substitute a machine for man in hostile environments, cut costs by replacing expensive hand labour with cheap dependable machines, and provide versatile, all purpose robots or mechanical devices at predictable costs. Robot is such a machine which does not get tired, does not go on strike and does not demand increase in salary. 

          Robots can perform a variety of jobs such as welding and painting a car, house cleaning, cutting the grass of a lawn, working in nuclear plants or travelling to space. They can also play chess, work as a watchman, cut the wool of a sheep and pluck fruits from trees.

          Robots of higher level are capable of adapting to changes in environment. They are also capable of making decisions with the help of computers. A more complex robotive device in modern transportation is the automatic aircraft pilot which can control routine flights. An android robot named Shaky Robot was developed at Stanford Research Institute in California to do a variety of research jobs.

          Japan has the largest number of robots in the world. The United States of America, Britain, Germany, Sweden, Italy, Poland, France, India, etc are also using robotic devices for different purposes. All robotic devices are controlled by computers.