Why does lightening occur when the thunder takes place in the atmosphere of earth?

Earth is supposed to be zero potential. Above earth surface, there is a vast atmosphere where there is flow of air. Whenever air moves nearby the ground, friction gets raised and electric charge is induced in the air. When there is loss of negative charge particle electron, air gets negatively charged. The same process goes on repeating. In a long run, air carries lots of negative charge in the form of the cloud. As we know there is always attraction between the negative and positive charge. We know the ground acts as a zero potential. Whenever the charge carrying cloud goes very near to the tall objects like tree or tower or hill, then the negative charge cloud induces the positive charge at the top of tall object. Slowly, there is attraction. As a result, negative charge come in contact with the positive charge and tremendous friction takes place. At the moment, great sound is produced which we call thunder and the electrical energy get changed into the heat and light. Since the light travels at very high speed, we see first light and only then the sound. We have so many misconceptions about the thunder and lightning. People think that the axe gets fell during the lightening which is not a fact. Actually, there is a flow of electric charge towards the ground with a very high speed and gets terminate at the zero potential of earth. We have developed the earthing so as to save our life from the dangerous situation of lightning and thunder.

Why does sound produce while clapping?

When we clap with our hands, kinetic and mechanical energy are changed into sound energy at that moment. When we clap with our two hands, the palms get very much closer all of sudden and the air between the palms gets compressed suddenly.  When we go clapping, it happens that the air sometimes gets compressed while other time it gets loosed. Which cause the friction and that friction takes the form of sound energy and reach up to our ear. According to the conservation of energy, the energy neither be created or nor be destroyed. Instead it changes its form from one to another. Here also, the kinetic energy due to the motion of our hands, change in to the sound.

Wonderful human body facts

-A man has over 10000 million neurons in his brain. This is more than the number of stars in the Andromeda galaxy.

-The human brain can store 100 trillion bits of information compared to one trillion of a computer.

-When a pin pricks our skin the nerves transmit the message to the central neuraxis and back to the effected part at the speed of more than 3 x 10⁶mph.

-In a year, a person heart beats 40000000 times.

-If all the blood vessels in the human body were laid end to end, they would stretch more than 15000 kms.

-The red blood cells are produced at the rate of 3 million per second by the bone marrow.

-A men's sense of smell is at least 2000 times more sensitive than his sense of taste. His tongue can detect only five basic tastes while his nose can distinguish more than100000 different smells.

-The liver, body's second largest organ has been estimated to have about 500 functions. 80% of the liver can be respected without altering its function.

Compiled by Sunita Subedi

B.Sc. Third Year Physics

DEMONSTRATION OF RELATION BETWEEN ATOMIC PRESSURE AND BOILING POINT OF A LIQUID:

          A liquid boils when its saturated vapour pressure becomes equal to the external pressure on the liquid. When that happens, it enables bubbles of vapour to form throughout the liquid; those are the bubbles you see when a liquid boils.

If the external pressure is higher than the saturated vapour pressure, these bubbles are prevented from forming, and you just get evaporation at the surface of the liquid.

But at different pressures, water will boil at different temperatures. For example, at the top of Mount Everest the pressure is so low that water will boil at about 70°C. Depressions from the Atlantic can easily lower the atmospheric pressure in the UK enough so that water will boil at 99°C - even lower with very deep depressions.

Whenever we just talk about "the boiling point" of a liquid, we always assume that it is being measured at exactly 1 atmosphere pressure. In practice, of course, that is rarely exactly true.

All liquids, at any temperature, exert a certain vapour pressure. The vapour pressure can be thought of as the degree to which the liquid molecules are escaping into the vapour phase. The vapour pressure increases with temperature, because at higher temperature the molecules are moving faster and more able to overcome the attractive intermolecular forces that tend to bind them together. Boiling occurs when the vapour pressure reaches or exceeds the surrounding pressure from the atmosphere or whatever else is in contact with the liquid.

Human heart

The heart is a large hollow muscular organ in the human body. It is a major organ of the circulatory system. It is located in the middle of the chest between lungs. The heart is made up of special muscles known as cardiac muscle. Blood supplies oxygen and nutrients to the body.  On an average, the heart pumps about 7600 liters of blood and beats around 100000 times in a day. The heart of a newly born body weights only 20 grams.

Structure of the heart

          The heart is the muscular cone shaped organ, enclosed by the heart wall. It is divided into separate right and left section by a wall called the septum. The heart wall and the septum are formed by the cardiac muscle. Each of the section is divided into upper and lower compartment.

Universe

The Universe is the space/region/place that has no limit. The infinitely large space even the imagination cannot reach its boundary. When I was a child, I have one question that, “   what is there outside the universe?” It is because we have seen the limited two dimension figure of space in our books. But today I can’t imagine its dimension.

            Universe itself and its entities are the mysterious for scientist also. There are lots more things to know about it and lots more things to discover. There is dark as well as bright matter in the Universe. Bright matters consist of the celestial bodies such as stars, planets, satellites, asteroids, meteors etc. The unseen part of the universe is the dark matter. One question arises that why the unseen objects are considered as the matter.  As scientist had reached the nano region, the unseen space might contain the microscopic particles, and other types of waves and energies.

History of Speed of Light

The speed of light in vacuum is a fundamental property of nature. Determination of the speed of light was great challenge for the scientist. Many attempts were made for its detection. In 1667 Galileo Galilee made an experiment. Two observers A and B were kept on two hilltops with lamps. The lamps were initially covered. Observer A uncovers the lamp thereby sending the light to B and B uncovers the next lamp when he saw the light from A. The time interval for the covering and uncovering the lamps was noted. Then the velocity of light is calculated as

C = 2x/t, where x = distance between two lamps

                                t = time noted

The earliest method failed as the time interval was very much small. This experiment failed and Galileo concluded that the speed of light is finite but very high.

                Danish astronomer Roemer in 1675 succeeded to determine the speed of light by recording the date and time of eclipse of one of Jupiter's satellite. The value was 2.3x10⁸ meter per second which was small then present value. The terrestrial method was performed by French physicist Fizeau in 1849 and this was improved by Foucault in 1869. It was further modified by Michelson in 1927. The speed of light was 2.997927x10⁸meter per second.

                It is interested to know that speed of light was already estimated in Vedic age by the Hindu philosopher.