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Posted by Sheetal Gupta 5 years, 7 months ago
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Yogita Ingle 5 years, 7 months ago
When the temperature is increased, the atoms of the material vibrate and it makes the valence electrons present in the valence band to shift to the conduction band. This in turn increases the conductivity of the material. When the conductivity of the material increases, it means that the resistivity decreases and so the current flow increases. Thus some insulators at room temperatures changes to conductors at high temperature. For insulators they have a negative temperature co – efficient. So the value of temperature co –efficient of resistivity, α is negative.
Posted by Ramadevi Chinthakindi 5 years, 7 months ago
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Yogita Ingle 5 years, 7 months ago
Principles of Metallurgy:
The metallurgical process can be classified as the following:
1. Crushing and grinding: The first process in metallurgy is crushing of ores into a fine powder in a crusher or ball mill. This process is known as pulverization.
2. The concentration of ores: The process of removing impurities from ore is known as a concentration of minerals or ore dressing. In metallurgy, we concentrate the ores mainly by the following methods.
3. Hydrolytic method: In this method, we pour the ore over a sloping, vibrating corrugated table with grooves. A jet of water is allowed to flow over the surface. The denser ore particles settle in the grooves, and the impurities are washed away by water.
4. Magnetic separation: In this case, the crushed ore is placed on a conveyor belt. This belt rotates around two wheels in which one of the wheels is magnetic, and therefore the magnetic particles get attracted to the magnetic wheel and fall apart from the non-magnetic particles.
5. Froth floatation: In this process, we take the crushed ore in a large tank which contains oil and water. A current of compressed air is passed through it. The ore gets wet by oil and is separated from the impurities in the form of froth. Ore is lighter, and so it comes on the surface and impurities are left behind.
Posted by Tanu Yadav 5 years, 7 months ago
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Yogita Ingle 5 years, 7 months ago
The process of taking air into and expelling it from the lungs is called breathing.
The action of breathing in and out is due to changes of pressure within the thorax, in comparison with the outside. This action is also known as external respiration. When we inhale the intercostal muscles (between the ribs) and diaphragm contract to expand the chest cavity. The diaphragm flattens and moves downwards and the intercostal muscles move the rib cage upwards and out.
This increase in size decreases the internal air pressure and so air from the outside (at a now higher pressure that inside the thorax) rushes into the lungs to equalise the pressures.
When we exhale the diaphragm and intercostal muscles relax and return to their resting positions. This reduces the size of the thoracic cavity, thereby increasing the pressure and forcing air out of the lungs.
Posted by Aayan Ahmed 5 years, 7 months ago
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Yogita Ingle 5 years, 7 months ago
Enzymes are soluble protein molecules that can speed up chemical reactions in cells. These reactions include respiration, photosynthesis and making new proteins. For this reason enzymes are sometimes called biological catalysts.
Yogita Ingle 5 years, 7 months ago
Oxidation: A chemical reaction which involves addition of oxygen or removal of hydrogen or loss of electron(s) is called as oxidation.
2Mg + O2 →2MgO (addition of oxygen)
H2S + Br2 → 2HBr + S (removal of hydrogen)
Fe2+ → Fe3+ + e- (loss of electron)
Posted by Muskan Yadhuvanshi 5 years, 7 months ago
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Yogita Ingle 5 years, 7 months ago
Universal indicator is a brown coloured solution containing a mixture of indicators, that can be added to any substance to determine its pH. It changes colour in different pH environments. At pH range of 8−11, the colour is blue.
Posted by Muskan Yadhuvanshi 5 years, 7 months ago
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Yogita Ingle 5 years, 7 months ago
Phenolphthalein:
Colour in acidic solution: Colourless
Colour in basic solution: Pink
Posted by Amit Barik 5 years, 7 months ago
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Meghna Thapar 5 years, 5 months ago
If a number of resistors are joined together so that the current flowing across each resistor is the same, then the resistances are said to be connected in series. As shown in Fig, consider three resistances R1, R2 and R3 connected in series. ... Let, Rs be the equivalent resistance of the combination.
Let resistance are connected in series R1, R2 and R3 then resultant resistance will be equal to the R1+R2+R3.
The current flowing through each resistance is the same. The potential difference across the ends of the series combination is distributed across the resistances.
The equivalent resistance (Rs) of a series combination containing resistances R1, R2, R3... is
Rs = R1 + R2 + R3 +...
The equivalent resistance is greater than the greatest resistance in the combination.
Posted by Chirag Khera 5 years, 7 months ago
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Yogita Ingle 5 years, 7 months ago
Limitations of Mendeléev’s classification
- No fixed position could be assigned to hydrogen in the Periodic Table.
- Isotopes discovered long after Mendeléev periodic classification of
elements imparted a challenge to Mendeleev’s Periodic Law. - The atomic masses of elements did not increase in a steady manner while going from one element to other which made it difficult to predict the number of elements that could be discovered between two elements.
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Posted by Sarwarth Malla 5 years, 7 months ago
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Meghna Thapar 5 years, 5 months ago
Reactant concentration, the physical state of the reactants, and surface area, temperature, and the presence of a catalyst are the four main factors that affect reaction rate. Reaction rates can be affected by several factors, including concentration, temperature, surface area and presence of a catalyst. Increasing concentration increases the number of effective collisions. Increasing the surface area of a solid reactant exposes more of its particles to attack. This results in an increased chance of collisions between reactant particles, so there are more collisions in any given time and the rate of reaction increases.
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Posted by Kashika Khuranaa.. ? 5 years, 7 months ago
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When the guard cells lose water, they shrink and the stomata will close. Guard cells also have large vacuoles. The cells that surround the guard cells are known as subsidiary or accessory cells. The guard cells in dicot plants are kidney shaped and dumbbell shaped in monocots.
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पं.अखिल पाठक 5 years, 7 months ago
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Yogita Ingle 5 years, 7 months ago
Exchange of gases take place in plants through stomata pores. Plants take carbon dioxide gas during day time to perform their photosynthesis process .The oxygen gas which is released during photosynthesis process is used by plants in a small amount for their respiration . And during night time plants take oxygen gas for their respiration and release carbon dioxide form during the process of photosynthesis.
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Posted by Sneha Tiwari 5 years, 7 months ago
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Meghna Thapar 5 years, 6 months ago
- The ration of potential difference applied between the ends of a conductor and the current flowing through it is a constant quantity called resistance.
- The property of the conduct due to which it opposes the flow of current through it is called as resistance of conductor.
- 1 ohm is the resistance of a conductor such that when a potential difference of 1 volt is applied to its ends, a current of 1ampere flows through it.
Posted by Anushka ???? 5 years, 7 months ago
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Suryansh Singh 5 years, 7 months ago
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