IIT JEE प्रश्न और उत्तर का अभ्यास करें

प्र: The modulus of elasticity for mild steel is approximately equal to 2344 0

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    210 kN/mm2
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    100 kN/mm2
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    80 kN/mm2
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    10 kN/mm2
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उत्तर : 1. "210 kN/mm2"
व्याख्या :

Answer: A) 210 kN/mm2 Explanation: It is useful to have a property of a material that is independent of the size of the sample and can be use to compare its elastic properties with another - this is called the Modulus of Elasticity for the material. The modulus of elasticity is defined as:   Modulus of elasticity = Stress / Strain   There are three types of moduli. They are : (a) the Young Modulus - tensile and compression longitudinal stress (b) the shear modulus - a shearing stress (c) the bulk modulus - volume changes of the specimen.

प्र: Maximum fixation of solar energy is done by 1404 0

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    Fungi
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    Protozoa
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    Bacteria
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    Green plants
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उत्तर : 4. "Green plants"
व्याख्या :

Answer: D) Green plants Explanation:

प्र: Ticks and mites are actually 1408 0

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    Arachnids
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    Insects
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    Myriapods
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    Crustaceans
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उत्तर : 1. "Arachnids"
व्याख्या :

Answer: A) Arachnids Explanation:

प्र: IUPAC full form 1567 0

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    Indian Union of Pure and Applied Chemistry
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    International Union of Postal and Application Corporation
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    International Union of Pure and Applied Chemistry
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    International University of Poland And Combodia
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उत्तर : 3. "International Union of Pure and Applied Chemistry"
व्याख्या :

Answer: C) International Union of Pure and Applied Chemistry Explanation: IUPAC stands for International Union of Pure and Applied Chemistry.   A chemical nomenclature is a set of rules to generate systematic names for chemical compounds. The nomenclature used most frequently worldwide is the one created and developed by the International Union of Pure and Applied Chemistry (IUPAC).

प्र: What is the bond order of O2? 1390 0

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    1.5
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    2
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    2.5
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    1
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उत्तर : 2. "2"
व्याख्या :

Answer: B) 2 Explanation: The number of bonds between a pair of atoms is called the bond order. Bond orders can be calculated from Lewis structures, which are the heart of the valence-bond model. Oxygen, for example, has a bond order of two. When there is more than one Lewis structure for a molecule, the bond order is an average of these structures. The bond order in sulfur dioxide, for example, is 1.5  the average of an S-O single bond in one Lewis structure and an S=O double bond in the other. In molecular orbital theory, we calculate bond orders by assuming that two electrons in a bonding molecular orbital contribute one net bond and that two electrons in an antibonding molecular orbital cancel the effect of one bond. We can calculate the bond order in the O2 molecule by noting that there are eight valence electrons in bonding molecular orbitals and four valence electrons in antibonding molecular orbitals in the electron configuration of this molecule. Thus, the bond order is two.

प्र: The term 'fourth estate' is used in reference to 1209 0

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    The Executive
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    The Press and news paper
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    Parliament
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    The Judiciary
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उत्तर : 2. "The Press and news paper"
व्याख्या :

Answer: B) The Press and news paper Explanation: Thomas Carlyle attributed the origin of the term to Edmund Burke, who used it in a parliamentary debate in 1787 on the opening up of press reporting of the House of Commons of Great Britain.

प्र: Which of the following statements about aldosterone is NOT correct? 2702 0

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    Aldosterone increases sodium reabsorption by increasing the number of Na+-K+ ATPase pumps in the luminal membrane of the proximal tubule.
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    Aldosterone is stimulated by decreased plasma sodium levels and increased plasma potassium levels.
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    Aldosterone is produced in the adrenal cortex.
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    Aldosterone increases the number of passive sodium channels in the luminal membrane of the distal tubule and collecting duct, thus aiding sodium reabsorption.
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उत्तर : 1. "Aldosterone increases sodium reabsorption by increasing the number of Na+-K+ ATPase pumps in the luminal membrane of the proximal tubule."
व्याख्या :

Answer: A) Aldosterone increases sodium reabsorption by increasing the number of Na+-K+ ATPase pumps in the luminal membrane of the proximal tubule. Explanation: Aldosterone, the main mineralocorticoid hormone, is a steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands and colon.

प्र: Is rusting a physical or chemical change? 2186 0

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उत्तर :
व्याख्या :

In chemistry rusting is called as oxidation. Oxidation is a chemical process where metal gains oxygen and become oxide. In rusting the Iron ore make a chemical reaction with the oxygen in the presence of water and environmental or atmospheric moisture to produce an Iron oxide. Iron oxide is otherwise called as rust. The rusting of iron is a chemical change because it is two substances reacting together to make a new substance.    Rusting would only be a physical change if iron molecules remained pure iron throughout the process.

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