Alternating current class 12 key concepts || A C class 12 key concepts || Alternating current formulas class 12 ||

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Diagonal Relationship between Beryllium and Aluminium || Relation between Beryllium and Aluminium

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  Diagonal Relationship between Beryllium and Aluminium The ionic radius of Beryllium (Be 2+) is estimated to be nearly 31 pm; the charge/radius ratio Or e/m ratio is nearly the same as that of the Al 3+ ion. Hence beryllium resembles aluminium in these ways. Some of the similarities are given below: » Like Aluminium, Beryllium(be) is not readily attacked by acids H+ donor because of the formation of an oxide film on the surface of the metal by reacting with oxygen, i.e. they are rendered passive by nitric acid. » Beryllium hydroxide[[Be(OH)4]2] dissolves in excess of alkali to give a beryllate ion, [ Be(OH)4]2– just as aluminium hydroxide[Al(OH)3] gives aluminate ion, [Al(OH)4] » The chlorides of metals beryllium and aluminium have Cl– bridged chloride structure in vapour phase. Both the chlorides are soluble in organic solvents and are strong as Lewis acids They are used as Friedel Craft catalysts. » Beryllium(Be) and aluminium(Al) ions have strong tendency to form complexes, (Be...
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Why should a magnesium ribbon be cleaned before burning in air?

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Ques 1 : Why should a magnesium ribbon be cleaned before burning in air? Ans 1: Magnesium is very reactive metal like (Na, C a, etc.). When it expose to air it reacts with oxygen to form a layer magnesium oxide (Mg O) on its surface.                  Mg +  O 2 → 2 Mg O This layer of magnesium oxide is quite stable and prevents further reaction of magnesium with oxygen. The magnesium ribbon is cleaned by sand paper to remove this layer so that the underlying metal can be used for the reaction. «« Chapter 1 NCERT Solution                                            Next question »»
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Banking of road || Inclination of road || Physics || Class 11 ||

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                    Banking of road The maximum permissible velocity with which vehicle can go round a level curved road without skidding depends on the coefficient of friction ( μ)  between the tyres and the road The value of  μ  decreases when road is smooth or tyres of the vehicle are worn out or the road is wet and so on. Thus force of friction is not a reliable source for providing the required centripetal force to the vehicle. A safer course of action would be to raise outer edge of the curved road shove the inner edge. By doing so, a component of normal reaction of the road shall be spared to provide the centripetal force. This phenomenon of raising outer edge of the curved road above the inner edge is called banking of roads . It's facilitates vehicles to turn without slipping. Three forces are acting on the vehicle as shown in Figure below.  (i) Weight mg of the vehicle acting vertically downwards.  (ii)...
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A rocket with a lift-off mass 20,000 kg is blasted upwards with an initial acceleration of 5.0 m/s². Calculate the initial thrust (force) of the blast.

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Ques : A rocket with a lift-off mass 20,000 kg is blasted upwards with an initial acceleration of 5.0 m/s². Calculate the initial thrust (force) of the blast. Ans : Mass of the rocket, m = 20,000 kg Initial acceleration, a = 5 m/s2 Acceleration due to gravity, g = 10 m/s2 Using Newton’s second law of motion, the net force (thrust) acting on the rocket is given by the relation: F – mg = ma F = m (g + a) = 20000 × (10 + 5)  = 20000 × 15  = 3 × 10^5 N. 
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Computer science MCQ questions Class 12 Python

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 SECTION-A 1. When reading a file line by line, the exact contents can be printed by: (A) Using readline ( ) (B) Using readlines ( ) (C) Using ‘,’ after every print statement (D) Both (A) & (B) 2. Choose the correct Python expression for the following mathematical expressions p+q/(r+s)4 (A) p+q / math.pow ((r+s), 4) (B) p+q/(r+s)^4 (C) p+q / math.pow (r+s,4) (D) (p+q) / math.pow (r+s) 3. Identify the correct statement for opening text file data.txt in total folder of c:drive in read mode. (A) F = open (“c:\\total\\data.txt”, “r”) (B) F = open (“c:\total\data.txt”, r) (C) F = open (“c:\total\data.txt”) (D) F = open (“\total\data.txt”, “r”) 4. A valid combination of atoms and operators forms a Python (A) Statement (B) Expression (C) Condition (D) None of these. 5. The default file open mode in Python is (A) Write (B) Read (C) Append (D) Read/write 6. In Python, a block is executed in an .................... (A) Function (B) Module (C) Py file (D) Execution frame 7. Consider ...
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