Doubtly
@Doubtly · Joined Feb 2021
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- Consider a circular coil of wire carrying current I, forming a magnetic dipole. The magnetic flux through an infinite plane that contains Answer: (a) φ_i = -φ₀ Magnetic field lines always form closed loops (there are no magnetic monopoles), so the net magnetic flux through any... 1
- Two moles of an ideal gas with Cp/Cv = 5/3 are mixed with 3 moles of another ideal gas with Cp/Cv = 4/3. Answer: (c) 1.42 For a mixture, add the heat capacities of the gases. For an ideal gas, C_V = R/γ - 1 and C_P = γ C_V . Gas 1 ( n₁ = 2,\ γ₁... 1
- A long solenoid of radius R carries a time (t) dependent current I(t) = I0t(1 − t). A ring of radius 2R is placed coaxially near its middle. Correct answer is option C 1
- A 60 HP electric motor lifts an elevator with a maximum total load capacity of 2000 kg. If the frictional force on the elevator is 4000 N, Correct option is d) 1.9 ms P = Fv + Mgv Applied power = 4000 × v + 20000 v 60 × 246 = 4000 v + 20000 v v = 1.865 v = 1.9 m/s Rounding it of... 1
- A polarizer-analyzer set is adjusted such that the intensity of light coming out of the analyzer is just 10 % of the original intensity. Correct Answer is option D 18^o Intensity after polarisation through polaroid = I_ocos²φ So, 0.1I_o = I_ocos²φ ⇒cosφ = √0.1 ⇒cosφ = 0.316 Si... 1
- Give an example of a double displacement reaction other than the one given in Activity 1.10 Reaction Between silver nitrate (AgNO3) and Sodium chloride (NaCl) is an example of double displacement reaction. Here Silver donates its io... 1
- Why does the colour of copper sulphate solution change when an iron nail is dipped in it? When an iron nail dipped in the copper sulphate solution, iron displaces copper from the copper sulphate because iron is more reactive than... 1
- Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas In activity 1.7, gas collected in one of the test tubes is double of the amount collected in the other because water gets hydrolysed to rele... 2
- Write the reaction of the substance ‘X’ named in (i) above with water CaO + H2O → Ca(OH)2 2
- Name the substance ‘X’ and write its formula. The substance ‘X’ which is used in whitewashing is quick lime or Calcium Oxide and its formula is CaO. 1
- Sodium hydroxide solution in water reacts with hydrochloric acid solution to produce Sodium chloride solution and water. NaOH + HCl → NaCl + H₂O 2
- Solutions of Barium chloride and Sodium sulphate in water react to give insoluble Barium sulphate and solution of Sodium chloride. BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl 2
- Write a balanced equations for the following chemical reactions. i) H2 + Cl2 → 2HCl ii)3BaCl2 + Al2(SO4)3 → 2AlCl3 + 3BaSO4 iii) 2Na + 2H2O → 2NaOH + 2
- Why should a magnesium ribbon be cleaned before burning in air? Magnesium rubber should be cleaned before burning in air because Magnesium metal reacts with the atmospheric oxygen and forms Magnesium Oxid... 1
- Imagine yourself to be XYZ, a member of a women Self- Help Group. Analyse the ways through 3 which your group provides loan to the members. (i) Self Help Groups pool their savings. (ii) A typical SHG has 15-20 members, usually belonging to one neighbourhood, who meet and save reg... 1
- The magnitude of vectors OA, OB and OC in the given figure are equal.
- An inductor coil stores 64 J of magnetic field energy and dissipates energy at the rate of 640 W when a current of 8A is passed through it. Correct Answer is 0.2 Explaination :: 1
- JEE MAIN 2021 (Aug-Sept Attempt) Answer Key & Solutions