A child staying in a coastal region tests the drinking water and also the sea water with his tester. He finds that compass needle deflects more in the case of sea water. Can you explain the reason?

When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

Assertion:Reverse osmosis is used in the desalination of sea water. Reason: When pressure more than osmotic pressure is applied, pure water is squeezed out of the sea water through the membrane.

Among the following, find.the number of correct statements? Sea water and trees are big sinks for carbondioxide. Geater the chemical oxygen demand (COD) and biochemical oxygen demand (BOD) values, greater is the extent of pollution. Lesser the threshold limit value (TLV), greater the toxicity Ozone layer present in stratosphere acts as protective umbrella form hamful sunrays. Flouride ion in drinking water is detected by using zirconium alizarin - S dye. The dye loses its colour in the presence of flouride. Human ear can tolerate the sound upto the intensity 60 decibles.

Assertion (A) Role of oceans In supplying usable water is quite Important.Reason (R). : : When the sea water reaches us, In various other forms of sources of water, it is no more saline.

Answer carefully: (a) Two large conducting spheres carrying charges Q_(1) and Q_(2) are brought close to each other. Is the magnitude of electrostatic force between them exactly given by Q_(1),Q_(2)//4pi epsilon_(0)r^(2) , where r is the distance between their centres? (b) If Coulomb’s law involved 1//r^(3) dependence (instead of would Gauss’s law be still true ? (c) A small test charge is released at rest at a point in an electrostatic field configuration. Will it travel along the field line passing through that point? (d) What is the work done by the field of a nucleus in a complete circular orbit of the electron? What if the orbit is elliptical? (e) We know that electric field is discontinuous across the surface of a charged conductor. Is electric potential also discontinuous there? (f) What meaning would you give to the capacitance of a single conductor? (g) Guess a possible reason why water has a much greater dielectric constant (= 80) than say, mica (= 6).

Divya suggested some methods to separate mixtures given below. Are they correct?Find whether they are possible or not. Give reasons. Pure water can be obtained from sea water by the process of filtration.