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ENGINEERING PHYSICS- II QP CODE: 948 SOLUTIONS with DETAILED ALLOCATION of MARKS OCT/NOV-2019 Answer Key

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ENGINEERING PHYSICS- II QP CODE: 948 SOLUTIONS with DETAILED ALLOCATION of MARKS OCT/NOV-2019 Answer Key ENGINEERING PHYSICS- II QP CODE: 948 SOLUTIONS WITH DETAILED ALLOCATION OF MARKS OCT/NOV-2019 Answer key Q.No Part-A Marks 1. Mean free Path: The average distance between two successive collisions of the gas molecules. 2 2. Specific heat capacity of a gas at constant pressure: Quantity of heat required to increase the temperature of 1 mole of gas through 1 kelvin when the 2 pressure is kept constant. 3. Critical temperature: The critical temperature of gas is defined as that temperature above which the gas cannot be 2 liquefied however great the pressure applied may be. 4. Laws of refraction: (i) The incident ray, refracted ray and the normal at the point of incidence are lying in the same plane 2 (ii) The ratio of sine of angle of incidence to the sine of angle of refraction is a constant for a pair of mediums, sin i/ sin r = constant. (Snell’s law). 5. LASER: Light Amplification by Stimulated Emission of Radiation. 2 6. Law of resistance when they are connected in parallel: When a number of resistance are connected in parallel, the reciprocal of the resultant resistance is 2 equal to the sum of the reciprocal of the individual resistance. (1/R =1/R1+1/R2+1/R3) 7. Fermi level: The maximum energy of the electrons in the filled levels of the valence band of a solid at 0K 2 temperature. 8. Three different configurations for a transistor used in electronic circuits: (i) Common Emitter configuration (CE) (ii) Common Base configuration (CB) 2 (iii) Common Collector configuration (CC) Q.No Part-B 9. Three properties of thermal radiation: (any 3 points) The nature of thermal radiation is similar to that of light. Following are some of the properties of thermal radiation. 1. Thermal radiation travels with the velocity of light, which is 3 × 108 ms-1. 2. Thermal radiation obeys the same laws of reflection, refraction etc., as light. 3. Thermal radiation travels through vaccum. 3 4. It obeys the law of inverse square, as light. 5. It travels in straight lines. 6. When thermal radiation falls on any body, which can absorb it, then converted into ordinary heat, which raises its temperature. 7. It is absorbed by dark rough surfaces and reflected by light smooth surface. 10. Adiabatic change: When the pressure and volume of a gas change, but no heat is allowed to enter or leave the gas, 1 this change is called as adiabatic change. 1 dQ = Change in internal energy + External work For a perfect gas, adiabatic change can be represented by the 1 γ γ γ equation, PV =a constant Also P1 V1 = P2 V2 11. Renewable sources of energy: Energy resources are sources of power that quickly replenish (fill again) themselves and can 3 be used again and again repeatedly. These energy resources are also called as infinite energy resources. Ex: Solar, Wind, Tidal, Geothermal, Bio mass, Hot dry rock, Chemical, etc. 12. Data acquisition of remote sensing: The schematic diagram of data acquisition is shown in the figure. In this process, five distinct elements are involved. They are 1. Energy Sources. 2 2. Propagation of energy through the atmosphere. 3. Energy interaction on earth surface. 4. Space borne sensors record the reflected energy. 5. Conversion of sensors data in the form of pictures or digital information. 1 13. Three advantages of IC’s: (any 3 points) 1. Extremely small physical size. Often the size is thousands of times smaller than discrete Circuit. 2. Low power consumption. 3 3. Easy replacement 4. Cost effective due to mass production of IC and less failure rate in mass production. 14. Fleming’s left hand rule: According to this rule, when the forefinger, middle finger and thumb of the left hand are stretched mutually perpendicular to each other and if the forefinger represents the direction of magnetic field, the 3 middle finger represents the direction of current in the conductor, then the thumb gives the direction of force acting on the conductor. 15. Intrinsic semiconductors: Semiconductors in pure form are called intrinsic semiconductor. 3 Example: Si, Ge Joule’s law of heating: 16. The quantity of heat developed ( H ) in a conductor is (i) directly proportional to the square of the current passing through the conductor ie H α I 2 (ii) directly proportional to the resistance of the conductor ie H αR 3 (iii) directly proportional to the time of flow of current ie H α t ie H α I2 Rt H = I2 Rt Q.No Part-C 17 Explain the process of conduction, convection and radiation: a) Conduction: In Conduction, the molecules of the body are responsible for the heat transfer. Here there is no actual movement of molecules from one place to another place. When a rod is heated at one end, the molecules 2 at the hot end vibrate about their mean position and transfer the heat energy to the neighboring molecules and thus the heat energy reaches the other end of the rod. Conduction is the process by which heat is transmitted from one point to another without the actual movement of the particles from their equilibrium positions. Conduction takes place in solids, liquids and gases. Convection:- In the case of heat transfer by convection, there is actual movement or motion of molecules of the fluid ( liquid or gas ).The portions of the fluid that get warmed up by contact with the heat source, expand and so move up through the body of the fluid due to the decrease in density. There is an inflow of cooler 2 molecules to take the place of heated mass of the fluid which has moved up. This circulatory motion of the fluid mass by which heat is transferred from place to place is called Convection. Convection is the process in which heat is transmitted from one place to the other by the actual movement of heated particles. Convection takes place only in liquids and gases. It cannot take place in solids. Radiation:- For heat transfer by radiation, no medium is required. The heat from the Sun is received by earth only by radiation. Both heat and light travel through space with same velocity and they are similar in nature. Both are generated and transmitted in the same way. They are transverse waves and 1 electromagnetic in character, but they differ in wavelength and frequency. The thermal radiations are detected in the 'infra-red'' region of the electro-magnetic spectrum. Radiation is the process by which heat energy is transmitted from one place to another without the aid of an intervening material medium. Derive an expression for the pressure of a gas on the basis of Kinetic theory of gases: 17.b) 1 1 1 1 1 17.c) The specific heat capacity of the gas at constant pressure is 31408 JK-1 per kg. mole. The ratio of specific heat capacities of a gas is 1.36. Calculate the specific heat capacity of the gas at constant volume and also the value of Universal gas constant ‘R’ for the gas. -1 1 Given: Cp = 31408 JK per kg. mole , γ = 1.36 γ = Cp/Cv 1.36 = 31408/Cv ; Cv = 31408/1.36 -1 Cv = 23094.117 JK per kg. mole. 2 Universal gas constant( R) = C - C ; R = 31408-23094.117 p v 2 R = 8313.882 JK-1 per kg. mole. 18. Carnot's Engine: a) Explanation and Carnot engine parts: 1 Diagram: 1 Pressure volume indicator diagram: 1 Working of Carnot engine: 1 Efficiency: η = (T1-T2) / T1 1 18. Linde's Process - Liquefaction of Air: b) Principle: Joule Thomson effect 1 Diagram: 2 2 Procedure: 18. Solar energy c) Solar energy Introduction: 1 Solar energy Explanation: 1 Thermal way and Photovoltaic way explanation: 2 Diagram: 1 19. Expression for the refractive index of the material of the prism: a) 1 2 2 19. Spontaneous emission and Stimulated emission: b) Spontaneous emission Spontaneous emission is the process of photon emission takes place immediately without any inducement during the transition of atoms from higher energy levels to lower energy levels. This is a random process in which the photons are emitted at different time. So, in the emitted radiation each photon has different phase and are incoherent. 2 The number of spontaneous transition (N sp) taking place per unit time per unit volume is directly proportional to the number of atoms in the higher energy level (N2). N = A N sp 2 where A is a constant known as the probability of spontaneous transition per unit time. Also it is called Einstein's co-efficient of spontaneous emission. Stimulated emission Einstein found a new process called stimulated emission to increase the number of transition of atoms from higher energy levels to lower energy levels. Stimulated emission is the process of photon emissions takes place by an inducement given by another photon incident on the atoms in higher energy levels. The energy of the photon emitted is equal to the energy of the photon incident. Consider an atom in the higher energy level(E2) when an external radiation of photon energy (E2-E1) is incident on the excited atom, the photon stimulates the atom to make transition from higher to lower energy level. As a result the same photon energy (E2-E1) is emitted in the form of radiation. During this process, the stimulating photon and the photon emitted by the excited atom are emitted simultaneously in the same direction. Hence they are identical in phase, direction and frequency and are coherent. This 2 process of stimulated emission is used to produce laser beam.
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