________________
2. Coulomb's law in electrostatics holds only for stationary
charges, which are points in size. When the same two charges located in air are placed in a dielectric medium without altering the distance between them, electrostatic force always decreases. A system of charge is said to be in equilibrium, if the net
force experienced by each charge of the system is zero. 5. Electrostatic force between two charges is not affected by the
presence of a third charge in their space." (c) Ibid. p.4 (461 14 3G1E {UD STT SÅ HELT TII) –
"A polythene piece rubbed rubbed with wool is found to have a negative charge 3 x 10-7 C. Estimate the number of electrons transferred from wool to polythene." Sol. Here, total charge transferred, q = - 3 x 10-7 C Charge on an electron, e = -1.6 x 10-19 C From quantization of charge, q= ne Therefore, number of electrons transferred, n=9/e=-3x 107 /
-3x10-19 1.6 x 10-19 = 1.875 x 1012. 46. (a) Gujarat State Board of Text books, Text book of Physics (Part - 2),
Std. xii, pp. 1,2 — ''The discoveries and the early understanding of the electrical and the magnetic phenomena, developed independently of each other. The pioneering experimental studies of early scientists like Oersted, Rowland and Faraday established the connections between the magnetic fields and the electric currents. A complete synthesis of the two groups of phenomena was achieved by the theoretical works of Maxwell and Lorentz, the synthesis being now called the electromagnetic phenomena. It was this deeper understanding of the electromagnetic phenomena, that led to the identification of light as electromagnetic waves. Further technological developments in the production, propagation and detection of the electromagnetic radiation's have revolutionized our global communication techniques. 1. Oersted's Obeservations In the, year 1819, a Danish school teacher named Oersted discovered that a magnetic field is produced surrounding a conductor carrying a current. If magnetic needle is suspended parallel to a conducting wire,
THÍ NGHI 319d-f4d-4, 2003
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