(a)State and prove Gauss's law of electrostatics. Derive its differential form. [12]
(b)Use Gauss's law to calculate the electric field due to a line charge. [5]
(c)A point charge of 1.8 µC is at the centre of a cubical Gaussian surface 55 cm on edge. What is the net electric flux through this surface? Use ε o = 8.854 × 10 -12 C 2 /N.m 2 . [3]
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Q. 3
(a)Analyze the RLC-series circuit using j-operator method and discuss its frequency response. Discuss the importance of this circuit. [14]
(b)Find the impedance of a circuit consisting of a 1.5 kΩ resistor, 5.0 µF capacitor and 50 mH inductor in series at a frequency of 10 kHz. [4]
(c)What are the advantages of A.C. mains supply? [2]
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Q. 4
(a)Describe the forward and reverse biased characteristics of a PN junction. [6]
(b)Explain the working of a bridge rectifier using a neat and labelled circuit diagram. [12]
(c)Why semiconductor devices are preferred over the vacuum tubes? [2]
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Q. 5
(a)What is meant by Compton Effect? Derive an expression for Compton shift in wavelength. [16]
(b)A beam of X-rays is scattered by a carbon target. At 45°from the beam direction the scattered X-rays have a wavelength of 2.2 pm. What is the wavelength of the X-rays in the direct beam? (Given that h = 6.626 X 10 -34 J.s, m e = 9.109 x 10 -31 kg and c = 2.998 x 10 8 m/s) [4]
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Q. 6
(a)Derive expressions for half-life and mean life of a radioactive substance. [15]
(b)The activity of a certain radionuclide decreases to 15 percent of the original value in 10 days. Find its half-life. [3]
(c)Give any two industrial or medical uses of radioisotopes. [2]
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Q. 7
(a)Differentiate between nuclear fission and fusion. [3]
(b)Draw a labelled diagram of a nuclear reactor and explain the functions of various parts. [13]
(c)Calculate the energy released in the following fission reaction induced by slow neutrons. 235 U + n → 140 Xe + 94 Sr + 2n Express your answer in MeV [Given that m( 235 U) = 235.043923 a.m.u., m( 140 Xe) = 139.921640 a.m.u., m( 94 Sr) = 93.915360 a.m.u., and 1 a.m.u. = 931.5 MeV/c 2 ] [4]
The 2015 CSS Physics paper set by the FPSC. Question wording only; questions marked “Not yet checked” have not been compared with the official paper yet.
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