The world of Physics is the world of nature- from the very big, the Universe to the smallest, namely the subatomic particles. Physics is a branch of science that deals with the constituents of the Universe, the forces between them and the effects of such forces.
In this sense, it can be said that Physics allows us to learn about nature at its most fundamental level. Here are few mind blowing Physics facts for kids, from past to present, from the very small to big things and the Physics involved in our everyday world that we do not realize but is fascinating and fun to learn.
Let’s dive straight into these mind blowing Physics facts, we hope that you like these facts and hike your interest in learning this weird and fun subject called ‘Physics’.
Here the list of 60 mind blowing physics facts for kids
A Peek into History: 10 mind blowing facts from the past
Why do we feel lighter when we are in water?
The answer to this question was first given by the Greek philosopher, Archimedes (287-212 BC) who thought of this when his bath overflowed as he stepped into it.
The Archimedes principle states that any object immersed in a fluid loses weight equal to the weight of the fluid it displaces. This same principle explains, why a piece of iron sinks in water while a huge ship floats.
The Archimedes Law of Lever
Archimedes was also the first to understand the principle of the lever, though man had used this simple implement for a long time. In fact, he is reported to have said, “Give me a place to stand and I will move the Earth with a lever”.
The best example of this law is a see-saw. Let us understand this law with examples.
Suppose you are playing see-saw with your friend in the park. Your friends weight is almost equal to you and also the distance of both of you from the centre(fulcrum) is equal, in this case, what will happen?
You both will find it difficult to lift each other as the force exerted by you and your friend is equal and the length of the lever i.e the distance from the centre is also equal.
To lift your friend upward or to push him down you need to exert a force which is greater than the force exerted by your friend. There are two ways you can achieve this-
- By increasing your weight
- By increasing the length of the lever i.e your distance from the centre (Fulcrum)
The invention of the telescope
Galileo (1564-1642) made many important contributions to Physics and Astronomy. He discovered the laws of falling bodies and also the motion of projectiles. In Astronomy, he was the first to use the telescopes for observing planets. He discovered several moons of Jupiter as well as valleys and mountains on the moon.
The genius who understood nature
Issac Newton (1642- 1727) is considered to be one of the greatest scientists of all times. He formulated the laws of motion and the laws of gravitation that explain the motion of the heavenly bodies.
There is a story ( possibly false! ) of his discovering the laws of gravitation watching an apple fall! His book Principia is thought to be the most significant work of all times.
The colour of the rainbow
Newton also established the modern study of light and made the first reflecting telescope. He was the first to show that sunlight was actually made up of seven colours.
Discovery of the radioactive waves
Madame Curie was the first person to win two Nobel Prizes in different subjects. Her first Nobel Prize was in Physics, in 1903, for research in radioactivity while her second Nobel Prize was in Chemistry, in 1911, for discovering radium and Polonium.
Incidentally, Curie’s first prize was shared with her husband Pierre, and her daughter Irene shared the 1935 Chemistry prize with her husband, Joliot!
The genius of Einstein
Perhaps the most well-known scientist of the 20th century is Albert Einstein. Einstein is well known for his theory of relativity. You must have come across his famous equation E= mC2.
His Special Theory of Relativity explained the true nature of light. He postulated that ‘the speed of light was independent of the speed of the observer and in fact, was the maximum speed by which information can be transferred’.
Confirming the Theory of Relativity
Einstein’s Theory of General Relativity explains the nature of space and time and is a more accurate theory of gravitation than Newton’s Laws of Gravitation. This theory, called by some the ‘most beautiful theory in Physics‘ was verified experimentally during the 1919 total solar eclipse by the astronomer Eddington.
The invention of transistor
John Bardeen became the first person to win two Nobel Prizes in the same field. In 1956, he got the Nobel Prize in Physics for inventing the transistor while in 1972, he got the Prize for developing the Theory of Super-conductivity.
The fun-loving scientist
Perhaps the most colourful figure in 20th-century Physics was Richard Feynman. He formulated the theory of how light interacts with atoms. He was also an accomplished bongo player and picked locks as a hobby!
In fact, Feynman got into trouble when he picked the locks in a safe containing the designs of the first atomic bomb during the Second World War!
10 mind blowing Physics about some numbers and tools
An ancient way of measuring things
Man has used different units to measure length, mass (weight) and time throughout history. The earlier units were based on standards that could change and were not permanent. For instance, the cubit, an early unit of length was the length from the elbow to the tip of the middle finger.
Introduction of the metric system
The metric system of units was introduced in France in the 1790s. The metre has been variously defined as one ten-millionth of the distance between the equator and the North Pole on al line through Paris or in terms wavelength of the light emitted by the element Krypton. It is now defined as the distance travelled by light in 1/299, 792, 458 of a second.
How big is the Universe?
The Universe is so large that measuring distances in kilometres makes little sense. Our Sun is 150 million km away while the next nearest star, Proxima Centauri is 40 trillion km away! Clearly measuring these distance in kilometres like measuring the distance from New York to London in micrometres!
How are distances in Astronomy measured?
Distances in Astronomy are measured in light-years. Light travels very far 299,792,458m in a second. Light from the Sun takes about 8 minutes to reach us. If we take the distance travelled by light in a year, we get a unit of length called the light year.
A Light year is roughly 9,461,000,000,000 (9461 billion) km. Thus, the Sun is about 8 light minute away and Proxima Centauri about 4.2 light-years from us. So what we see now of the Proxima Centauri was actually how it looked 4 years ago!
Another convenient measure of distance is the Astronomical Unit (AU) which is defined as the average distance between the Sun and our Earth, about 150 million km.
How old is the Universe?
Astronomers believe that the Universe that we live in began its life from a Big Bang about 10 billion years ago.
You must be wondering how the age and the size of the Universe have turned out to be magically the same number?
There is no mystery in it. Astronomers measure the age of the Universe and since we can only see the Universe to the distance from which light could have reached us since the Universe began, we get a size of 10 billion light-years.
The tiny world of atoms
In the world of atoms, distances are too small to measure in metres or even millimetres. For instance, an atomic nucleus has a size of a trillionth of a centimetre. That is eleven zeroes after the decimal point and then a one! A more appropriate unit to measure length is an angstrom.
One angstrom is 10 billionth of a centimetre. The size of an atomic nucleus is thus about one ten-thousandth of an angstrom.
Another common unit of length that is used frequently, nowadays, is a nanometre. A nanometre is a billionth of a metre and scientists are now making devices of this size. This technology is called Nanotechnology and holds great promise for the future.
The science behind light waves
Light waves allow us to see the world around us. However, light is only a small part of a whole electromagnetic spectrum that includes radio waves, microwaves, infrared, visible light, ultra-violet, X-rays and gamma rays. Visible light is the only part of the electromagnetic spectrum that we can perceive. Visible light has wavelengths around 5000 angstroms.
The physics behind radioactive waves
1) All forms of electromagnetic radiation travel at exactly the speed of light. The only difference between them is their wavelength or the distance between successive crests or troughs of the wave. Radio waves have wavelengths from 1 cm to about 1000m while X-rays are a billionth of a metre.
2) Of course, different electromagnetic radiations have different properties that make them useful or dangerous for us. For instance, we can use microwaves to cook food and X-rays to get images of our bones.
3) Some of the electromagnetic radiation like X-rays, gamma rays or even ultraviolet rays can be dangerous for living things. The ozone hole in our atmosphere is dangerous because it lets in too much ultra-violet radiation from the Sun that can cause damage to living creatures.
4) Radioactive waves are useful in dating archaeological and geological material. While radiocarbon dating is used to find out how old objects that were once living ( like pieces of wood, bone etc.) is potassium-argon dating used to determine the ages of rocks.
The gravitational force
We are all aware of the force of gravity that is responsible for not only the path of a cricket ball but also for the motion of planets.
Gravity is the only one of the four fundamental forces known to us. It is the weakest of the four forces and is attractive in nature. All objects that have a mass experience this force.
Fun facts about the magnetic force
The other everyday force is the electromagnetic force. We see electrical force at work when we see a streak of lightning while magnetic forces cause iron to be attracted towards a magnet. Our earth also has a very weak magnetic field that allows us to use a magnetic compass in case we get lost in a forest.
The electrical and magnetic forces, though seemingly different are actually known to be manifestations of one force, the electromagnetic force. It acts bodies that have a property called the electrical charge and is significantly stronger than the gravitational force.
Like charges repel each other and unlike charges attract each other. This force between charges is what is responsible for most of the chemical reactions and hence most of our everyday phenomena.
The other two fundamental forces are the strong nuclear and weak force. These forces only act in the domain of subatomic particles. These are responsible for the stability of atomic nuclei as also the decay of nuclei by radioactivity. Radioactivity is what nuclear bombs, as well as nuclear reactors, emit.
10 Mind blowing Physics facts about very big things
Fascinating facts about stars
Looking at the night sky especially from the mountain is an awesome experience. One sees thousands of ‘stars’. Though for us, all these are stars, astronomers place them in different groups depending on their properties. In fact, most of these glowing objects are not stars at all but are collections of stars called galaxies.
Our own galaxy, the Milky Way has about trillion stars. It is a spiral galaxy with several arms coiling around a central bulge that is about 10,000 light-years thick. The diameter of the disc is about 100,000 light-years.
Like our Earth, the Milky Way rotates about an axis passing through its poles. The period of rotation of our solar system is about 200 million years. Due to its rotation, the Solar System is moving at a speed of about 220 km/sec.
Facts about the biggest star in our Universe- The Sun
The most well-known star for us is our Sun. It is called a main-sequence star. The Sun and the other stars like it, give off huge amounts of energy. The source of this energy is nuclear reactions using hydrogen as fuel similar to what happens in thermonuclear (hydrogen) bombs. The Sun is about 5 billion years old.
As the Sun grows older, it becomes hotter and brighter. In about 3 billion years, it will be hot enough to boil our oceans.
After the Sun finishes all its hydrogen it will start expanding. It will engulf the planet Mercury and become a Red Giant. Oh, by the way- in about 5 billion years, the Sun would have swallowed our Earth too.
The big Red Giant
1) The Big Red Giant, as the name suggests is a gigantic star-typically 10 to 1000 times the size of our Sun. A Red Gaint also gives off much more energy than stars like our own Sun. In fact, most of the stars that you see at night are Red Giants because they glow very brightly and hence can be easily spotted.
2) The most massive of the Red Giants end up the most enigmatic objects in the Universe- black holes. These are extremely dense invisible objects that have so much gravitational attraction that not even light can escape from them. A black hole with the mass of our Sun will only be 3 km across.
The White Dwarf
1) When a star like our Sun has exhausted all the nuclear fuel in its core, it collapses under its own weight to become a very small and heavy object called a White Dwarf.
2) A White Dwarf typically is the size of our own Earth but has almost 70% of the mass of the Sun. If you work that out, it gives these objects a density of 600 million kg per cubic metre. That is a teaspoonful of this star weighs about 3000 kg.
3) Because these stars are so small, they are difficult to see with the naked eye. But astronomers can see them using their telescopes. In fact, the brightest star in the sky, Sirius A or Dogstar has a companion star which is a White Dwarf.
4) How did the astronomers first discover the White Dwarf companion Sirius?
In 1844, the German astronomer F Bessel detected that the motion of Sirius A was irregular. Since there was nothing to cause the irregularity, he proposed that there is an invisible companion star that exerts a gravitational pull on Sirius. This was indeed, discovered in 1862. Such stars that orbit each other are called Binary stars.
Facts about the Earth’s magnetic force- The Gravity
1) If you throw a ball upwards, it returns to the ground. Now suppose we throw the ball with a larger speed, then it will reach a higher point. If we continue this process, we can throw the object fast enough that it escapes the gravitational pull of the Earth. The speed is called the escape velocity and for our Earth, it is 11.2 km/sec while for the Moon, which is much lighter than the Earth it is only about 2.4 km/sec.
2) Escape velocity of a body depends on the gravitational pull of the body. Imagine a body that is so heavy that the escape velocity is the speed of light. Now since Einstein has told us that nothing can move faster than light, it is clear that nothing- you, a spaceship or even light can’t escape from this monstrous celestial object. Such an object is called a black hole.
The mysterious black hole
1) Since light, or for that matter any other form of electromagnetic radiation cannot escape from a black hole, astronomers use indirect methods of studying them. The black hole, because of its immense gravity sucks in matter from nearby objects. This matter while falling towards the black hole gives out radiation that can be observed.
2) The other way to detect a black hole is to see stars moving at enormous speeds around an invisible object. For instance, astronomers have observed about 20 stars orbiting the centre of our own galaxy at a speed of about 5 million km/hr. It is thought that the centre of our galaxy has a heavy black hole that is providing the gravity for the stars to move at such speeds.
The mighty Quasars
Quasars are relatively small objects that are usually found in the centre of galaxies. Quasars give out a lot of energy and are thought to be associated with black holes. In 1998, a Quasar was detected which gives out more than 30,000 times the energy emitted by our Milky Way and remember, the Milky Way has billions of stars.
The dusty snowballs
Comets, the heavenly messengers are also part of our Solar System. They are small objects of rock and ice that revolve around the Sun. As they approach the Sun, some of the ice becomes gas and together with the dust forms a huge tail. The most famous comet, Halley’s comet is seen every 76 years. In 1994, comet Shoemaker-Levy crashed into Jupiter creating fireballs the size of our Earth.
The small rocky planets
Asteroids are small planets in our Solar System that are mostly in a belt between Mars and Jupiter. They vary in size- the largest Ceres has a radius of about 500 km while most are no bigger than a grain of dust.
They are now believed to be remnants of a planet that could have been formed but could not because of the gravitational pull of nearby Jupiter.
The powerful telescopes
1) We observe the Universe by the telescope that could either be based on Earth in space. The biggest ground-based optical telescopes are on the top of Mauna Kea, a dormant volcano in Hawaii.
The Hubble Space Telescope was launched in 1990 and orbits the Earth producing images of the Universe that are many times sharper than those seen from the Earth.
2) Apart from the well-known optical telescopes that collect visible light, there are now telescopes that cover almost the whole range of the electromagnetic spectrum- from radio waves to gamma rays. These have proved to be immensely useful in increasing our understanding of the Universe.
10 Mind blowing Physics facts about very small things
The big world of small atoms
1) The basic building blocks of matter are atoms. An atom is the smallest particle of an element that would exhibit its chemical properties. Atoms are small by everyday standards- 10 million of them in a row would only measure 1 millimetre. Each element has a unique atom that gives it its unique properties.
2) Atoms of an element or of different elements can interact with each other to form all the substances that we see in nature around us- from waster to complicated proteins in our cells.
3) When two or more atoms combine they form a molecule. A molecule is the smallest part of a substance that has all the chemical properties of that substance. Each substance has a different kind of molecule and this is what gives us variety in nature.
Protons, nucleons and electrons
1) An atom can be thought of as a cloud of negative particles called electrons surrounding a very small nucleus. The nucleus is made up of positive particles called protons and neutral neutrons. The number of electrons and protons are equal, making the atom electrically neutral as a whole.
2) The nucleus is much smaller than the atom. If the atom was the size of a cricket field, then the nucleus would be the size of a pea.
3) Electrons are thought to be points in space, i.e they are believed to have no structure. They are among the lightest particles known to us. An electron weighs about a billionth, billionth, billionth of a gram of 10-27 grams. The electric charge of the electron is taken as negative unity and all other charges in the atomic world are measured in terms of this.
Facts about Quarks
1) Protons are about 1840 times heavier than electrons and carry one unit of positive charge. Protons are made up of even more fundamental particles called quarks.
2) There are six different kinds of quarks which are given fancy names by scientists to distinguish them. These are up, down, strange, charm, top and bottom. These names have nothing to do with their properties and are used only as labels.
3) Quarks have strange properties. Unlike all other subatomic particles which carry integral charge, quarks carry fractional charges (in units of the electron charge). For instance, the up quark carries a charge of +2/3 while the down quark has a charge -1/3. However, a proton is made up of 2 up quarks and a down quark, giving a net charge of +1.
Quarks are very tiny compared to the protons. If a proton is drawn as a ball of 1 cm size, the quarks will be thinner than the diameter of our hair.
The amazing light particles
1) Scientists believe that light or electromagnetic radiation is made up of small particles (or quanta) called photons. A photon is an example of a gauge particle. It has no mass or charge and always travels at the speed of light.
Photons of different forms of electromagnetic radiation have different energies. Thus, a radio wave photon is much less energetic than a gamma-ray photon.
Working of microscopes
1) You know that a microscope allows one to see very small objects like blood cells and bacteria. But since the atoms are much smaller (a bacteria is about 10000 times larger than an atom) scientists have developed special instruments to ‘see’ atoms and subatomic particles like electrons and protons.
2) The Electron Microscope is an instrument that uses a beam of electrons instead of light to form an image. Electron microscopes have been used to make images of a collection of atoms, though not yet of an individual atom.
The Large Hadron Collider
1) The largest particle accelerator in the world is the Large Hadron Collider (LHC) near Geneva in Switzerland. It has an underground tunnel (100m deep) which is 27km in circumference. Protons are accelerated to almost the speed of light in this tunnel. The magnets in the accelerator are superconducting and produce a magnetic field which is 1,00,000 times that of our Earth.
The Neutrino particles
Apart from the electrons and quarks, there are other fundamental particles like the neutrino. A neutrino is a particle that is neutral and is believed to have no mass. It feels no electromagnetic forces and is so small that it is hard to detect.
In fact, a neutrino can pass right through Earth without any interaction with any other particle. Neutrinos are produced in nuclear reactions like those happening in our Sun. Electrons and neutrinos belong to a type of fundamental particles called leptons.
The Leptons particles
Just like we have different kinds of quarks, there are different kinds of leptons. Apart from the electron, we have the muon and the tau particle, each carrying a unit negative charge like the electron and each with a neutrino associated with it. Thus, there is an electron neutrino, a muon neutrino and tau neutrino.
All the particles we have talked about have another strange property- all of them come with their twins called antiparticles. An antiparticle has the same mass as the particle but has the opposite charge and other properties.
For instance, a positively charged positron is the antiparticle of the electron and weighs exactly the same as the electron.
Molecules are held together by intermolecular forces. If these forces are strong between molecules of a substance, then the substance is a solid while weak forces lead to liquids and gases.
Something in-between: Physics facts about Our Everyday World
Newtons laws of motion
1) The motion of everything, from cars to planets is described by Newton’s three Laws of Motion. The First Law says that ‘an object will continue to move at a steady rate or be at rest unless an external force acts on it’. This is what makes us move forward when a car brakes suddenly.
This is also the law that allows a spacecraft to keep moving in a straight line without firing its rockets when it is far from the Earth or any other object in space.
2) Newton’s Second Law of motion relates to the acceleration of a body to the external force acting upon it. ‘For the same force, a heavier object moves more slowly than a light one’.
3) Newton’s Third Law simply states that ‘for every action, there is an equal and opposite reaction’. The action and reaction act on different bodies. When a rocket fires and throws out gases backwards at a great speed (action), the rocket itself experiences a force in the forward direction (reaction).
What is a machine?
A simple machine is a device that reduces the effort needed to do some piece of work. Man has used simple machines since antiquity. Examples of simple machines include lever, pulley, inclined plane and wheel and axle.
Possibly the first machine used by man was a lever to move heavy objects with the help of sticks of wood and a rock. All our complicated machines, from cars to huge bulldozers are built up parts that work on the principles of these simple machines.
Wheels and axle
As the name suggests, wheel and axle is a simple machine where a rod or axle is attached to the centre of a wheel. We see examples of this all around us – bicycles, cars and even the humble water tap. It is believed that the first wheel and axle was used in Mesopotamia for carts about 5,000 years ago.
When we water plants with a pipe, we see that the water takes a curved path before falling to the ground. This is called projectile motion and is the same path as is taken by a bomb fired from a cannon. Do you know, for the cannon shot to go the maximum distance, the cannon should be inclined at 45 degrees to the horizontal.
Newtons Law of Gravitation
1) Newton’s Law of Gravitation tells us that ‘objects experience a force between them decreases as the square of the distance between them’. We know that the Earth’s gravity decreases as we go away from the Earth. For instance, a one kg weight would weigh only 250g if we took it 6,400km (the radius of the Earth) up into space.
2) But interestingly, as we go down towards the centre of the Earth, the force of gravity decreases till it becomes zero at the centre. Actually, if we were to drop a body in a hole dug right through the centre of the Earth to the other side, it will oscillate like a pendulum.
3) All of us have experienced a light feeling in a lift as it goes down. What if the ropes holding the lift broke and it started falling freely? Then we would experience the same kind of weightlessness that astronauts feel in space. A freely falling body is weightless.
Needle vs blunt nail
Why do you think it is easy to pierce things with a needle but harder to do it with a blunt nail? The answer to this is in the pressure exerted. Pressure is defined as the force that acts on a unit area. A needle, with its fine tip, has more pressure for the same force than a blunt nail that has a larger tip.
It is the same principle that is used in tanks and bulldozers where instead of tyres we have tracks so that they don’t get stuck in loose mud. Their enormous weight is distributed over a larger area and thus a smaller pressure is exerted on the ground.
The force of friction
1) Whenever two surfaces are in contact with each other we get a force that opposes motion and is called friction. In most cases, friction is harmful as it leads to a loss of energy in the form of heat- the wheels of your cycle feel hot after you have ridden it. But friction is also useful sometimes, e.g, between our feet and the Earth. It allows us to walk without slipping.
2) A parachutist dropped from an aeroplane experiences a frictional force (in this case it is called atmospheric drag). The parachute increases the drag because of its large area. This allows the parachutist to attain a constant speed of descent called the terminal velocity.
Facts about surface tension
1) Have you wondered why water droplets are spherical in shape? The answer lies in the force of surface tension. Liquids behave as if their surface is covered with a membrane that has a tendency to shrink.
This shrinking force wants to make the surface area of the liquid a minimum. Since a sphere has the least surface area for a given volume, the natural shape of liquid drops is spherical.
2) Surface tension is also responsible for capillary action. Some of you might have seen kerosene lamps used in villages for light. The wick is a piece of cloth dipped in kerosene. The kerosene travels up the wick because of capillary action. The motion of water from the soil to the leaves in a plant is also dependent upon capillary action.
The Ripple effect
1) All of us are fascinated by the waves that grow outwards when we throw a stone in a pond. But did you know that there is no movement of the water outwards, only the disturbance flows out while the water only moves up and down? This motion of the disturbance is what is called wave motion.
2) There are two kinds of waves- longitudinal and transverse. In longitudinal waves, like sound waves, the motion of the particles is along the direction of the wave while in transverse waves, like waves on a stretched string, the motion of the particles is in a direction at right angles to the wave direction.
1) Lightning flashes travel at a fantastic speed of over 2500 km/sec and can be more than 30 km long. A typical lightning bolt can have a temperature of over 30,000-degree celsius and can discharge 5,000 megawatts of energy.
But since it lasts only for about a thousandth of a second, the total kilowatt-hours (units that you pay for in your electricity bill) is only about 1500 kilowatt-hours.
2) The lightning bolt heats the air along its path and this causes the air to expand very rapidly. The expanding air causes vibrations that we hear as thunder.
Physics at everyday work : 10 Physics facts about everyday things
1) Your computer monitor and television screen are both based on a device called the LED (Light-emitting diode). LED are more energy-efficient than LCD technology which allows to manufacture TV’s with compact sizes. There are three types of LED’s screens classified according to the configuration of LED lights behind the screen namely Direct-lit, Edge-lit and Full array.
LED screens with full array configuration are the most prefered by customers as they give a uniform colour distribution on the screen.
2) W Roentgen accidentally discovered X-rays in 1895. The electrons produced in a cathode ray tube are accelerated to very high speeds and hit a target to produce X-rays. Apart from being immensely useful for scientists studying metals and materials.
Too much exposure to X-rays can lead to cancer. Lead and other heavy metals are useful in stopping X-rays. Therefore, we see doctors operating the X-ray machines wearing heavy coats which have lead shields.
3) Though radioactive radiation is very dangerous for living things, doctors treat cancer with it. A small amount of radioactive material (usually cobalt) which gives off gamma rays is used in radiation therapy of cancer patients.
The gamma rays are made to hit the cancerous tumour and destroy it. Of other healthy cells in the neighbourhood of the tumour.
4) The microphone that we use to record our voice is based on the principle of electromagnetism. The sound energy in our voice makes a plate vibrate which determines how much current flows in a circuit.
This current can then be fed into a speaker where it operates an electromagnet. The variations in the current produce a varying magnetic field that vibrates a plate to produce sound.
5) The telephone was invented by Alexander Graham Bell in 1876. The telephone converts the sound energy of our voice into electrical energy in the mouthpiece and transmits the electric signal to the receiver. In the receiver earpiece, the electrical signals are reconverted back to sound that we hear.
6) The property of certain materials to magnetize and demagnetize easily is used in many devices. In an audiotape, the magnetic particles on the tape are aligned magnetically in response to the magnetic force of the recording head.
The electric current that is supplied by the microphone, just like in a telephone mouthpiece, in turn, governs the magnetic force of the head.
7) A helicopter, unlike an aeroplane, can take off and land vertically. It produces an upward force by using its rotors that create an airflow above them that provides the lift.
The aeroplane wings have the same function and as the aeroplane moves forward at high speeds, the airflow along the wing surface provides the lift necessary for take-off.
8) Rocket engines that power spaceships and missiles work on the principle of action and reaction. Propellant fuel, which is either solid or liquid is burnt and escapes from the back at huge speeds (up to 5000 m/sec in some rockets).
This provides a reaction that pushes the rocket forward and allows it to attain the speed needed to escape the Earth’s gravitational force.
9) The next generation of automobiles will be running on fuel cells. Fuel cells are cells that produce electricity directly from a chemical reaction. The most promising one is the hydrogen fuel cell, where hydrogen is used as a fuel to produce an electric current used to run the car engine.
The waste product of such a cell is water that is formed by the waste hydrogen combining with oxygen from the air. The cost of such cells is falling rapidly and there are some prototypes already in use in the USA.
10) A refrigerator in your kitchen has a refrigerant that is placed in a sealed system. The refrigerant evaporates into a gas thereby cooling the inside and then condenses back into a liquid.
The heat generated when it condenses is given the atmosphere. This is the reason why the back of the fridge is warm and has metal fins to lose heat more efficiently. The whole process requires a compressor to compress the gas.