Sushmita Sen, the first Indian to win the Miss Universe pageant held at Manila, Philippines 1994 was born on November 19, 1975 in Hyderabad, Andhra Pradesh. Daughter of an Air Force Commander her family of Bengali origin was posted in Nagpur, then Jorhat, and finally in Delhi. She did her schooling with English Honors predominantly in the Air Force Silver …
Read More »Why is liquid ammonia used in ice plants?
Liquid ammonia acts as a refrigerant in ice plants. Evaporation of a liquid needs heat energy. When liquid ammonia vapourizes, it absorbs large quantities of heat without changing its temperature. For these reasons, ammonia is widely used as a refrigerant. About 17 g of liquid ammonia absorbs 5,700 calories of heat from the surrounding water. This cools the water and …
Read More »Why is it harder to walk uphill than downhill?
It is harder to walk uphill than downhill because you must lift the weight of your body and to do this requires greater energy than that needed for walking on the level. To create this greater energy your muscles require to give extra lift, your heart has more work to do to feed the blood cells and remove their waste …
Read More »Why is it cooler at higher altitudes?
High altitudes normally begin at 1500 metres above sea level. At such altitudes, the atmospheric pressure is considerably lower than at sea level. To give some examples: the pressure at sea level is 14.7 pounds per square inch and it decreases through 4.3 psi at 30,000 ft to 1.6 psi at 50,000 ft. Because of this, the air expands as …
Read More »Why is hat-making called millinery?
Long ago, the best hats and headdresses in Europe were made in Milan, Italy. A citizen of Milan was called Milaner, and although the spelling of the word has changed, a hat maker is still called a milliner, wherever he or she lives, and the hats the milliner makes are called millinery.
Read More »Why is glass transparent?
These interactions depend on the nature of the light and the nature of the material. For instance, light falling on a leaf encounters many pigment molecules, predominantly chlorophyll. These molecules absorb light from the red and blue ends of the visible spectrum. The remaining light is scattered back because molecules in a leaf are tightly packed and so, we see …
Read More »Why is glass brittle?
Ordinary glass is soda-lime glass and is a mixture of silicates of sodium, potassium, calcium and aluminium etc. It is brittle because its molecular structure is composed of tetrahedral crystals. These crystals do not have a good large-area orderly crystalline structure. Therefore, when it is under stress, the structure gets ruptured.
Read More »Why is Einstein famous?
Albert Einstein is famous for his Theories of Relativity which say that nothing in the universe is absolutely still and that all motion is connected all or comparable. Einstein worked out a method of measuring the speed of moving objects, using the three dimension of space-length, height and thickness-and adding the fourth dimension of time. The three space dimensions tell …
Read More »Why is earthing necessary for electrical appliances?
As it’s a safety factor, earthing is essential and mandatory. It’s an electrical connection between the exposed metallic parts of an electrical appliance or installation and the earth, regarded to have zero potential. Proper earthing provides an alternative and easy path for leakage or faulty current to flow. It ensures that any exposed conductive part of the appliance does not …
Read More »Why is calcium sulphate hemihydrates called Plaster of Paris?
Plaster of Paris is obtained by heating gypsum or calcium sulphate dihydrate to about 140-180 degree Celsius. When heated to such a temperature, gypsum forms Plaster of Paris. The name is derived from the large deposits of gypsum in the Montmartre hill in Paris.
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