Question 1.
\nIf the pressure and the volume of certain quantity of ideal gas are halved, then its temperature
\n(a) is doubled
\n(b) becomes one-fourth
\n(c) remains constant
\n(d) is halved
\nAnswer:
\n(b) becomes one-fourth
\nAccording to ideal gas law
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-1M-Q1.jpg\")
<\/p>\n
Question 2. Question 3. Question 4. Question 5. Question 6. Question 7. Question 8. Question 9. Question 10. Question 1. Answer: Question 2. Question 3. Question 4. Answer:<\/p>\n Question 5. Question 1. Answer: 2. Work done by adiabatic process Question 2. Answer: Clausius statement: 2. Carnot\u2019s cycle: Step 2: Gas undergoes adiabatic expansion from (P2<\/sub>, V2<\/sub>, T1<\/sub>) to (P3<\/sub>, V3<\/sub>, T2<\/sub>)<\/p>\n Step 3: The gas release heat Q2<\/sub> to cold reservoir at T2<\/sub>, by isothermal compression from (P3<\/sub>, V3<\/sub>, T2<\/sub>) to (P4<\/sub>, V4<\/sub>, T2<\/sub>).<\/p>\n Step 4: To take gas into initial state, work is done on gas adiabatically [(P4<\/sub>, V4<\/sub>, T2<\/sub>) to (P1<\/sub>, V1<\/sub>, T1<\/sub>)]. Efficiency of Carnot\u2019s engine: Question 3. Explain your answers. Question 4. Answer:<\/p>\n Question 5. Answer: Question 6.<\/p>\n Answer: 2. According to 1st<\/sup> law of thermodynamics Question 7. Answer: 2. T2<\/sub> = 0\u00b0C = 273K Question 8. Answer: 2. T. = 27\u00b0C = 27 + 273 = 300k Question 9. Answer: 2. The efficiency of heat engine \u03b7 = 1 – \\(\\frac{T_{2}}{T_{1}}\\). The efficiency will be 100% if T2<\/sub> = OK, both those conditions cannot be attained practically. So art engine can\u2019t have 100% efficiency.<\/p>\n Question 10. Answer: Question 1. Question 2. Question 3. Question 4.
\nThe ideal gas equation connecting pressure (P), volume (V) and absolute temperature (T) is
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-1M-Q2.jpg\")
\nwhere kB<\/sub> is the Boltzmann constant and N is the number of molecules.
\nAnswer:
\nc) PV = kB<\/sub>NT
\nAccording to ideal gas equation,
\nPV = NkB<\/sub>T.<\/p>\n
\nWhich of the following laws of thermodynamics forms the basis for the definition of temperature?
\n(a) First law
\n(b) Zeroth law
\n(c) Second law
\n(d) Third’law
\nAnswer:
\n(b) Zeroth law
\nThe Zeroth law of thermodynamics gives the definition of temperature.<\/p>\n
\nWhich of the following is a true statement?
\n(a) The total entropy of thermally interacting systems is conserved
\n(b) Carnot engine has 100% efficiency
\n(c) Total entropy does not change in a reversible process.
\n(d) Total entropy in an irreversible process can either increase or decrease.
\nAnswer:
\n(c) Total entropy does not change in a reversible process.<\/p>\n
\nIn a given process of an ideal gas, dW = 0 and dQ < 0. Then for the gas
\n(a) the temperature will decrease,
\n(b) the volume will increase
\n(c) the pressure will remain constant
\n(d) the temperature will increase
\nAnswer:
\n(a) From first law of thermodynamics
\ndQ = dU + dW
\ndQ = dU (if dW = 0)
\nSince, dQ < 0
\ndU < 0
\nor Ufinal<\/sub> < Uintial<\/sub>
\nHence, temperature will decrease.<\/p>\n
\nAn electric fan is switched on in a closed room will the air of the room be cooled?
\nAnswer:
\nNo. Infact speed of air molecules will increase and this results in increase in temperature.<\/p>\n
\nWhen an iron nail is hammered, if becomes hot. Why?
\nAnswer:
\nThe kinetic energy of hammer gets converted in to heat energy which increases temperature of iron nail.<\/p>\n
\nIdentify the thermodynamic process in which temperature of system may increase even when no heat is supplied to the system.
\nAnswer:
\nAdiabatic process.<\/p>\n
\nWhich thermodynamic variable is defined by first law of thermodynamics?
\nAnswer:
\nInternal energy<\/p>\n
\nThe door of an operating refrigerator kept open in a closed room. Will it make the room cool?
\nAnswer:
\nNo. The room will be slightly warmed.<\/p>\nPlus One Physics Thermodynamics Two Mark Questions and Answers<\/h3>\n
\nA Carnot engine working between 300K and 600K has a work output of 800J per cycle. Find the amount of energy consumed per cycle<\/p>\n\n
\nEfficiency of carrots engine
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-2M-Q1.jpg\")
\nEfficiency also can be written as
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-2M-Q1.1.jpg\")
\n\u2234 input power = 1600 J.<\/p>\n
\nA carnote\u2019s engine is made to work between 200\u00b0C and 0\u00b0C first and then between 0\u00b0C and minus 200\u00b0C. Compare the values of efficiencies in the two cases.
\nAnswer:
\nCase -1:
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-2M-Q2.jpg\")
\n= 1 – 0.577
\n= 0.42 = 42%
\nCase – 2:
\n\u03b7 = 1 – \\(\\frac{73}{473}\\)
\nT2 = -200 = 73k
\n= 1 – 0.26 = 0.73
\n= 73%
\nT1<\/sub> = 0 = 273k.<\/p>\n
\nMatch the following
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-2M-Q3.jpg\")
\nAnswer:
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-2M-Q3.1.jpg\")
<\/p>\n
\nWhat is the value of specific heat capacity of gas in<\/p>\n\n
\n
\nIs the function of refrigerator against the second law of thermodynamics? Explain.
\nAnswer:
\nNo. The refrigerator transfers heat from the inside space to outer atmosphere, at the expense of external work supplied by the compresser fed by electric supply.<\/p>\nPlus One Physics Thermodynamics Three Mark Questions and Answers<\/h3>\n
\nHeat is supplied to a system, but its internal energy does not increase<\/p>\n\n
\n1. Isothermal process.<\/p>\n
\nLet an ideal gas undergoes adiabatic charge from (P1<\/sub>, V1<\/sub>, T1<\/sub>) to (P2<\/sub>, V2<\/sub>, T2<\/sub>). The equation for adiabatic charge is
\nPV\u03b3<\/sup> = constant = k
\nie; P1<\/sub>V1<\/sub>\u03b3<\/sup> = P2<\/sub>V2<\/sub>\u03b3<\/sup> = k _____(a)
\nThe work done by
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-3M-Q1.jpg\")
\nfrom equation (a) P1<\/sub>V1<\/sub>\u03b3<\/sup> = P2<\/sub>V2<\/sub>\u03b3<\/sup> = k
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-3M-Q1.1.jpg\")
\nSubstituting ideal gas equation.
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-3M-Q1.2.jpg\")
<\/p>\n
\nA heat engine is a device which effectively converts heat energy into mechanical energy.<\/p>\n\n
\n1. Kelvin – Plank statement:
\nNo process is possible whose sole result is the absorption of heat from a reservoir and complete conversion of heat into work.<\/p>\n
\nNo process is possible whose sole result is the transfer of heat from a colder object to hotter object.<\/p>\n
\nThe Carnot cycle consists of two isothermal processes and two adiabatic processes.
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-3M-Q2.jpg\")
\nLet the working substance in Carnot\u2019s engine be the ideal gas.
\nStep 1: The gas absorbs heat Q1<\/sub> from hot reservoir at T1<\/sub> and undergoes isothermal expansion from (P1<\/sub>, V1<\/sub>, T1<\/sub>) to (P2<\/sub>, V2<\/sub>, T1<\/sub>).<\/p>\n
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-3M-Q2.1.jpg\")
<\/p>\n
\nA thermo flask contains coffee. It is violently shaken. Considering the coffee as a system:<\/p>\n\n
\nAnswer:<\/p>\n\n
\nIt is predicted by meteorologists that global warming will result in the flooding of oceans due to the melting of ice caps on the earth.<\/p>\n\n
\n
\nWater is heated in an open vessel.<\/p>\n\n
\n
\n1. Isobaric
\n2. First law of thermodynamics
\n3.
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-3M-Q5.jpg\")
<\/p>\n\n
\n1. Molar specific heat at constant volume is the heat required to raise the temperature of I mol substance by IK at constant volume.<\/p>\n
\n\u2206Q = \u2206U + PAV
\nIf \u2206Q heat is absorbed at constant volume (\u2206V = 0).
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-3M-Q6.jpg\")
\nFrom ideal gas equation for one mole PV = RT. Differentiating w.r.t. temperature (at constant pressure
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-3M-Q6.1.jpg\")
\nEquation (4) – Equation (1), we get
\nCP<\/sub> – CV<\/sub> = R.<\/p>\n
\nA heat engine is a device which converts heat energy into work.<\/p>\n\n
\n1. Ideal gas.<\/p>\n
\nT1<\/sub> = 100\u00b0C = 373K
\nEfficiency \u03b7 = I – \\(\\frac{T_{2}}{T_{1}}=I-\\frac{273}{373}\\)
\n\u03b7 = 0.27
\n\u03b7 = 27%.<\/p>\n
\nA gas is taken in a cylinder. The walls of the cylinder is insulated from the surroundings<\/p>\n\n
\n1. Adiabatic. A thermodynamic process in which no heat enters or leaves the system.<\/p>\n
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-3M-Q8.jpg\")
\n= 300 \u00d7 41.5 – 1<\/sup>
\n= 300 \u00d7 41\/2<\/sup>
\n= 600K
\nrise in temperature = 600K – 300K = 300K.<\/p>\n
\nRaju brought a motor pump from a shop. The efficiency of the motor pump is printed on the label as 60%.<\/p>\n\n
\n1. Efficiency means that, 60% of the total energy received is converted into useful work.<\/p>\n
\nCategorise into reversible and irreversible process<\/p>\n\n
\nReversible process \u2192 (3), (4), (6) and (9)
\nIrreversible process \u2192 (1), (2), (5), (7), (8) and (10)<\/p>\nPlus One Physics Thermodynamics NCERT Questions and Answers<\/h3>\n
\nA geyser heats water flowing at the rate of 3.0 litres per minute from 27\u00b0C to 77\u00b0C. If the geyser operates on a gas burner, what is the rate of consumption of the fuel if its heat of combustion is 4.0 \u00d7 104<\/sup> Jg-1<\/sup>?
\nAnswer:
\nVolume of water heated = 3.0 litre per minute
\nmass of water heated, m = 3000 g per minute
\nincrease in temperature, \u2206T = 77\u00b0C – 27\u00b0C = 50\u00b0C
\nspecific heat of water, c= 4.2Jg-1<\/sup> \u00b0<\/sup>C-1<\/sup>
\namount of heat used, Q = mc \u2206T
\nor Q = 3000 g min-1<\/sup> \u00d7 4.2Jg-1<\/sup>
\n\u00b0<\/sup>C-1<\/sup> \u00d7 50\u00b0C
\n= 63 \u00d7 104<\/sup>J min-1<\/sup>
\nrate of combustion of fuel = \\(\\frac{63 \\times 10^{4} \\mathrm{Jmin}^{-1}}{4.0 \\times 10^{4} \\mathrm{Jg}^{-1}}\\)
\n= 15.75gmin<\/span>-1<\/sup>.<\/p>\n
\nWhat amount of heat must be supplied to 2.0 x 10-2<\/sup>\u00a0kg of nitrogen (at room temperature) to raise its temperature by 45\u00b0C at constant pressure? (Molecular mass of N2<\/sub> = 28, R = 8.3 J mol-1<\/sup> K-1<\/sup>).
\nAnswer:
\nm = 2 \u00d7 103<\/sup> kg-1<\/sup> = 20g,
\n\u2206T = 45\u00b0C, M = 28
\nR = 8.3 J mol-1<\/sup> K-1<\/sup>, M = 28
\nNumber of moles, n = \\(\\frac{m}{M}=\\frac{20}{28}=\\frac{5}{7}\\)
\nSince nitrogen is diatomic,
\n\u2234 CP<\/sub> = \\(\\frac{7}{2}\\)
\nR = \\(\\frac{7}{2}\\) \u00d7 8.3 J mol-1<\/sup>K-1<\/sup>
\nNow, \u2206Q = nCP<\/sub> \u2206T
\n= \\(\\frac{5}{2}\\) \u00d7 \\(\\frac{7}{2}\\) \u00d7 8.3 \u00d7 45J = 933.75J.<\/p>\n
\nA cylinder with a movable piston contains 3 moles of hydrogen at standard temperature and pressure. The walls of the cylinder are made of a heat insulator, and the piston is insulated by having a pile of sand on it. By what factor does the pressure of the gas increase if the gas, is compressed to half its original volume?
\nAnswer:
\nP2<\/sub>V2<\/sub>\u03b3<\/sup> = P1<\/sub>V1<\/sub>\u03b3<\/sup>
\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-Textbook-Questions-Q3.jpg\")
<\/p>\n
\nA steam engine delivers 5.4 \u00d7 108<\/sup> J of work per minute and services 3.6 \u00d7 109<\/sup>J of heat per minute from its boiler. What is the efficiency of the engine? How much heat is wasted per minute?
\nAnswer:
\nWork done per minute, output = 5.4 \u00d7 108<\/sup>J
\nHeat absorbed per minute, input = 3.6 \u00d7 109<\/sup>J
\nEfficiency, \u03b7 = \\(\\frac{5.4 \\times 10^{8}}{3.6 \\times 10^{9}}\\) = 0.15
\n%\u03b7 = 0.15 \u00d7 100 = 15
\nHeat energy wasted\/ minute = Heat energy absorbed\/minute – Useful work done\/minute
\n= 3.6 \u00d7 109<\/sup> – 5.4 \u00d7 108<\/sup>
\n= (3.6 – 0.54) \u00d7 109<\/sup> = 3.06 \u00d7 109<\/sup>J.<\/p>\n
![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-Textbook-Questions-Q6.jpg\")
<\/p>\n![\"Plus](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/08\/Plus-One-Physics-Chapter-Wise-Questions-and-Answers-Chapter-12-Thermodynamics-Textbook-Questions-Q7.jpg\")