SAI'S SCIENCE AND MATHS CLASSES

Schwarzschild radius a Simple derivation If  the radius of a spherical body is less than Schwarzschild radius  it is called a black hole. And for a black hole the escape speed is equal to the speed of light. Schwarzschild radius , r s = 2GM / C 2    Usually the solution is obtained from EFE (Einstein’s Field Equation ) Proof For a planet the escape speed is related to its mass and radius , this is obtained by equating kinetic energy to the gravitational potential energy V escape 2  = 2GM / R So for a black hole   C 2 =2GM / R And R= r s Therefore r s = 2GM / C 2    

Dear Students Now it is time for SA2 The important questions on Carbon and its Compounds I am sharing with you Please click the following link  Carbon and its Compounds Regards

SA 1  Chemistry Points to Remember During electrolysis of water hydrogen @ cathode and oxygen @ anode (in the ratio 2:1) Colour of potassium nitrate is yellow ;  nitrogen di oxide is a brown fume formed during thermal decomposition of KNO 3  Gypsum, plaster of paris, blue vitriol(Cu SO 4 ), washing soda have water of crystallization  Amalgam is a metal in Mercury Galvanization coating metal with Zn Lustrous non metal is Iodine Liquid non metal is Br Liquid metal is Hg pH is the measure of acidic or basic character of a medium It determines the amount of hydronium ion in the medium Oxidation is loss of electron ; reduction is gain Electrolysis is a redox reaction Na OH is formed from brine solution by Chlor alkali process Carbonates and bicarbonates liberate CO 2  when treated with an acid Very dilute Nitric acid gives hydrogen with Mg and Mn only Hydrogen is used in the preparation of Margarine and chlorine in making PVC and CFCs Th...

Short description on Magnetic effect (class IX) The magnetic effect of electric current was discovered by Hans Christian Oersted . The magnetic field strength ( B ) is determined by the strength of the current The magnetic strength decreases as we move away from the conductor The magnetic field lines (imaginary) created by a long conductors is in the form a concentric circle with the axis of conductor at the centre The direction of magnetic field in a current carrying wire can be determined by Right Hand Thumb rule or Cork Screw rule.  SI unit of Magnetic field is Tesla  other unit is Gauss .

Short description on Magnetic effect (class IX) The magnetic effect of electric current was discovered by Hans Christian Oersted . The magnetic field strength ( B ) is determined by the strength of the current The magnetic strength decreases as we move away from the conductor The magnetic field lines (imaginary) created by a long conductors is in the form a concentric circle with the axis of conductor at the centre The direction of magnetic field in a current carrying wire can be determined by Right Hand Thumb rule or Cork Screw rule.  SI unit of Magnetic field is Tesla  other unit is Gauss .

1) The power rating and voltage rating of a device are 600W, 200V Find a) current rating b) resistance offered by the device c) energy consumed in 1 hr Ans: a) Power =VI I=P/V= 3 A b) R=V/I= 200/3 ohm c) E=Power x time=600x60x60= 2160000 J 2) Two wires one of copper and other of Nichrome have same length and resistance Which wire will be thicker? Justify Ans: resistivity=Resistance x Area / length since length and resistance is the same for both the wires we can compare their area The Nichrome wire, since an alloy will be having more resistivity , will be thicker. 3) A 15 ohm resistance wire is cut in to 3 equal pieces and then connected in parallel across a 5V battery Find a) current through each wire b) effective resistance  Ans: resistance is directly proportional to length of the wire if it is cut in to 3 equal pieces resistance of each piece will be equal to 5 ohm effective resistance of parallel combination  (1/R)=(1/R 1 )+(1/R 2 )+(1/R 3 ) ...

Coulombs law is Inverse square law Since force is a vector the principle of superposition involves vector addition Electric field is actually the stress experienced on the point by an electric charge, it is the force experienced on a unit positive charge placed at that point. F=qE Unit of electric field is N/C Electric field is known by other terms such as flux density and intensity of electric field it also have an inverse square relation with distance  Electric field lines never passes through a metal so inside the conductor the electric field E=0 Electric field can be considered as the negative potential gradient E=-dV/dr By Gauss theorem E.A=q/epsilon not there fore E=q /A  X epsilon not