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Assertion & Reason

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50 questions · timed · auto-graded

Question 11 Mark
Assertion : Air quickly leaking out of a balloon becomes coolers
Reason : The leaking air undergoes adiabatic expansion.
Answer
(a) Adiabatic expansion produces cooling.
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Question 21 Mark
Assertion : Reversible systems are difficult to find in real world.
Reason : Most processes are dissipative in nature
Answer
(a) In a perfectly reversible system, there is no loss of energy. Losses can be minimised, friction can be reduced, the resistance in L-C oscillating system can also be negligible. But one cannot completely eliminate energy losses. This makes a perfectly reversible system, an ideal.
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Question 31 Mark
Assertion : Air quickly leaking out of a balloon becomes coolers
Reason : The leaking air undergoes adiabatic expansion.
Answer
(a) Adiabatic expansion produces cooling.
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Question 41 Mark
Assertion : Reversible systems are difficult to find in real world.
Reason : Most processes are dissipative in nature
Answer
(a) In a perfectly reversible system, there is no loss of energy. Losses can be minimised, friction can be reduced, the resistance in L-C oscillating system can also be negligible. But one cannot completely eliminate energy losses. This makes a perfectly reversible system, an ideal.
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Question 51 Mark
Assertion : Air quickly leaking out of a balloon becomes coolers
Reason : The leaking air undergoes adiabatic expansion.
Answer
(a) Adiabatic expansion produces cooling.
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Question 61 Mark
Assertion : Reversible systems are difficult to find in real world.
Reason : Most processes are dissipative in nature
Answer
(a) In a perfectly reversible system, there is no loss of energy. Losses can be minimised, friction can be reduced, the resistance in L-C oscillating system can also be negligible. But one cannot completely eliminate energy losses. This makes a perfectly reversible system, an ideal.
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Question 71 Mark
Assertion : Thermodynamic process in nature are irreversible.
Reason : Dissipative effects can not be eliminated.
Answer
(a) In reversible process, there always occurs some loss of energy. This is because energy spent in working against the dissipative force is not recovered back. Someirreversibleprocess occur in nature such as friction where extra work to cancel the effect of friction. Salt dissolves in water but a salt does not separate by itself into pure salt and pure water.
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Question 81 Mark
Assertion : Thermodynamic process in nature are irreversible.
Reason : Dissipative effects can not be eliminated.
Answer
(a) In reversible process, there always occurs some loss of energy. This is because energy spent in working against the dissipative force is not recovered back. Someirreversibleprocess occur in nature such as friction where extra work to cancel the effect of friction. Salt dissolves in water but a salt does not separate by itself into pure salt and pure water.
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Question 91 Mark
Assertion : Thermodynamic process in nature are irreversible.
Reason : Dissipative effects can not be eliminated.
Answer
(a) In reversible process, there always occurs some loss of energy. This is because energy spent in working against the dissipative force is not recovered back. Someirreversibleprocess occur in nature such as friction where extra work to cancel the effect of friction. Salt dissolves in water but a salt does not separate by itself into pure salt and pure water.
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Question 101 Mark
Assertion : When a bottle of cold carbonated drink is opened, a slight fog forms around the opening.
Reason : Adiabatic expansion of the gas causes lowering of temperature and condensation of water vapours.
Answer
(a) When a bottle of cold carbonated drink is opened. A slight fog forms around the opening. This is because of adiabatic expansion of gas causes lowering of temperature and condensation of water vapours.
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Question 111 Mark
Assertion : When a bottle of cold carbonated drink is opened, a slight fog forms around the opening.
Reason : Adiabatic expansion of the gas causes lowering of temperature and condensation of water vapours.
Answer
(a) When a bottle of cold carbonated drink is opened. A slight fog forms around the opening. This is because of adiabatic expansion of gas causes lowering of temperature and condensation of water vapours.
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Question 121 Mark
Assertion : When a bottle of cold carbonated drink is opened, a slight fog forms around the opening.
Reason : Adiabatic expansion of the gas causes lowering of temperature and condensation of water vapours.
Answer
(a) When a bottle of cold carbonated drink is opened. A slight fog forms around the opening. This is because of adiabatic expansion of gas causes lowering of temperature and condensation of water vapours.
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Question 131 Mark
Assertion : In adiabatic compression, the internal energy and temperature of the system get decreased.
Reason : The adiabatic compression is a slow process
Answer
(d) Adiabatic compression is a rapid action and both the internal energy and the temperature increases.
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Question 141 Mark
Assertion : The isothermal curves intersect each other at a certain point.
Reason : The isothermal change takes place slowly, so the isothermal curves have very little slope.
Answer
(e) As isothermal processes are very slow and so the different isothermal curveshavedifferent slopes so they cannot intersect each other.
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Question 151 Mark
Assertion : In adiabatic compression, the internal energy and temperature of the system get decreased.
Reason : The adiabatic compression is a slow process
Answer
(d) Adiabatic compression is a rapid action and both the internal energy and the temperature increases.
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Question 161 Mark
Assertion : The isothermal curves intersect each other at a certain point.
Reason : The isothermal change takes place slowly, so the isothermal curves have very little slope.
Answer
(e) As isothermal processes are very slow and so the different isothermal curveshavedifferent slopes so they cannot intersect each other.
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Question 171 Mark
Assertion : In adiabatic compression, the internal energy and temperature of the system get decreased.
Reason : The adiabatic compression is a slow process
Answer
(d) Adiabatic compression is a rapid action and both the internal energy and the temperature increases.
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Question 181 Mark
Assertion : The isothermal curves intersect each other at a certain point.
Reason : The isothermal change takes place slowly, so the isothermal curves have very little slope.
Answer
(e) As isothermal processes are very slow and so the different isothermal curveshavedifferent slopes so they cannot intersect each other.
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Question 191 Mark
Assertion : In isothermal process whole of the heat energy supplied to the body is converted into internal energy.
Reason : According to the first law of thermodynamics $\Delta Q=\Delta U+p \Delta V$
Answer
(e) As there is no change in internal energy of the system during an isothermal change.Hence, the energy taken by the gas is utilised by doing work against external pressure. According to FLOT $\Delta Q=\Delta U+P \Delta V$Hence $\Delta Q=\Delta U=P \Delta V$Therefore, reason is true and assertion is false.
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Question 201 Mark
Assertion : In isothermal process whole of the heat energy supplied to the body is converted into internal energy.
Reason : According to the first law of thermodynamics $\Delta Q=\Delta U+p \Delta V$
Answer
(e) As there is no change in internal energy of the system during an isothermal change.Hence, the energy taken by the gas is utilised by doing work against external pressure. According to FLOT $\Delta Q=\Delta U+P \Delta V$Hence $\Delta Q=\Delta U=P \Delta V$Therefore, reason is true and assertion is false.
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Question 211 Mark
Assertion : In isothermal process whole of the heat energy supplied to the body is converted into internal energy.
Reason : According to the first law of thermodynamics $\Delta Q=\Delta U+p \Delta V$
Answer
(e) As there is no change in internal energy of the system during an isothermal change.Hence, the energy taken by the gas is utilised by doing work against external pressure. According to FLOT $\Delta Q=\Delta U+P \Delta V$Hence $\Delta Q=\Delta U=P \Delta V$Therefore, reason is true and assertion is false.
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Question 221 Mark
Assertion : The entropy of the solids is the highest
Reason : Atoms of the solids are arranged in orderly manner.
Answer
(a) Entropy is a measure of the disorder or randomness of the system. Greater the randomness, greater the entropy.
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Question 231 Mark
Assertion : Efficiency of a Carnot engine increase on reducing the temperature of sink.
Reason : The efficiency of a Carnot engine is defined as ratio of net mechanical work done per cycle by the gas to the amount of heat energy absorbed per cycle from the source.
Answer
b) Efficiency of cannot cycle $\eta=\frac{W}{Q_1}=1-\frac{T_2}{T_1}$, for Carnot engine when $T_2$ decrease $\eta$ increases.
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Question 241 Mark
Assertion : Zeroth law of thermodynamic explain the concept of energy.
Reason : Energy is dependent on temperature.
Answer
(e) Zeroth law of thermodynamics explain the concept of temperature. According to which there exist a scalar quantity called temperature which is property of all thermodynamic system.
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Question 251 Mark
Assertion : First law of thermodynamics is a restatement of the principle of conservation
Reason : Energy is fundamental quantity.
Answer
(c) First law of thermodynamics is restatement of the principal of conservation of energy as applied to heat energy.
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Question 261 Mark
Assertion : Work done by a gas in isothermal expansion is more than the work done by the gas in the same expansion, adiabatically.
Reason : Temperature remains constant in isothermal expansion and not in adiabatic expansion.
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Question 271 Mark
Assertion : An adiabatic process is an isoentropic process.
Reason : Change in entropy is zero in case of adiabatic process.
Answer
(a) Change in entropy, $\Delta S=\frac{\Delta Q}{T}$. In an adiabatic change, heat transfer $\Delta Q=0 . \therefore \Delta S=0$, or $S=$ constant i.e., entropy remains constant in an adiabatic process, or an adiabatic process is an isoentropic process.
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Question 281 Mark
Assertion : In an adiabatic process, change in internal energy of a gas is equal to work done on or by the gas in the process.
Reason : Temperature of gas remains constant in a adiabatic process.
Answer
(c) In an adiabatic process, no exchange of heat is permissible i.e., $\Delta Q=0$.As, $\Delta Q=\Delta U+\Delta W=0 \Rightarrow \Delta U=-\Delta W$.Also in adiabatic process, temperature of gas changes.
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Question 291 Mark
Assertion : The internal energy of an isothermal process does not change.
Reason : The internal energy of a system depends only on pressure of the system.
Answer
(c) First law of thermodynamics is restatement of the principal of conservation of energy as applied to heat energy.
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Question 301 Mark
Assertion : If an electric fan be switched on in a closed room, the air of the room will be cooled.
Reason : Fan air decrease the temperature of the room.
Answer
(d) If an electric fan is switched on in a closed room, the air will be heated because due to motion of the fan, the speed of air molecules will increase. In fact, we feel cold due to evaporation of our sweat.
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Question 311 Mark
Assertion : lt is not possible for a system, unaided by an external agency to transfer heat from a body at lower temperature to another body at higher temperature.
Reason : According to Clausius statement, "No process is possible whose sole result is the transfer of heat from a cooled object to a hotter object.
Answer
(a) Second law of thermodynamics can be explained with the help of example of refrigerator, as we know that refrigerator, the working substance extracts heat from colder body andrejects a large amount of heat to a hotter body with the help of an external agency i.e., theelectric supply of the refrigerator. No refrigerator can ever work without external supply of electric energy to it.
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Question 321 Mark
Assertion : A room can be cooled by opening the door of a refrigerator in a closed room.
Reason : Heat flows from lower temperature (refrigerator) to higher temperature (room).
Answer
(d) When the door of refrigerator is kept open, heat rejected by the refrigerator to the room will be more than the heat taken by the refrigerator from the room (by an amount equal towork done by the compressor). Therefore, temperature of room will increase and so it will bewarmed gradually. As according to 2- law of thermodynamics, heat cannot be transferred on its own, from a body at lower temperature to another at higher temperature.
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Question 331 Mark
Assertion : The heat supplied to a system is always equal to the increase in its internal energy.
Reason : When a system changes from one thermal equilibrium to another, some heat is absorbed by it.
Answer
(d) According to first law of thermodynamics, $\Delta Q=\Delta U+\Delta W=\Delta U+P \Delta V$. If heat is supplies in such a manner that volume does not change $\Delta V=0$ i.e., isochoric process, then whole of the heat energy supplied to the system will increaseinternal energy only. But, in any other process it is not possible.Also heat may absorbed or evolved when state of thermal equilibrium changes.
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Question 341 Mark
Assertion : Work and heat are two equivalent form of energy.
Reason : Work is the transfer of mechanical energy irrespective of temperature difference, whereas heat is the transfer of thermal energy because of temperature difference only.
Answer
(a) Heat is similar to work in that both represent ways of transferring energy. Neither heat nor work is an intrinsic property of a system, that is, we cannot say that a system contains a certain amount of heat or work.
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Question 351 Mark
Assertion : The specific heat of a gas is an adiabatic process is zero and in an isothermal process is infinite.
Reason : Specific heat of a gas in directly proportional to change of heat in system and inversely proportional to change in temperature.
Answer
(a) $\quad c=\frac{Q}{m \cdot \Delta \theta}$; a gas may be heated by putting pressure, so it can have values for 0 to $\infty$.$C_P$ and $C_V$ are it's two principle specific heats, out of infinite possible values.In adiabatic process $C=0$ and in isothermal process $C=\infty$.
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Question 361 Mark
Assertion : We can not change the temperature of a body without giving (or taking) heat to (or from) it.
Reason : According to principle of conservation of energy, total energy of a system should remains conserved.
Answer
(d) We can change the temperature of a body without giving (or taking) heat to (or from) it. For example in an adiabatic compression temperature rises and in an adiabatic expansion temperature false, although no heat is given or taken from the system in the respective changes.
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Question 371 Mark
Assertion : The entropy of the solids is the highest
Reason : Atoms of the solids are arranged in orderly manner.
Answer
(a) Entropy is a measure of the disorder or randomness of the system. Greater the randomness, greater the entropy.
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Question 381 Mark
Assertion : Efficiency of a Carnot engine increase on reducing the temperature of sink.
Reason : The efficiency of a Carnot engine is defined as ratio of net mechanical work done per cycle by the gas to the amount of heat energy absorbed per cycle from the source.
Answer
b) Efficiency of cannot cycle $\eta=\frac{W}{Q_1}=1-\frac{T_2}{T_1}$, for Carnot engine when $T_2$ decrease $\eta$ increases.
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Question 391 Mark
Assertion : Zeroth law of thermodynamic explain the concept of energy.
Reason : Energy is dependent on temperature.
Answer
(e) Zeroth law of thermodynamics explain the concept of temperature. According to which there exist a scalar quantity called temperature which is property of all thermodynamic system.
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Question 401 Mark
Assertion : First law of thermodynamics is a restatement of the principle of conservation
Reason : Energy is fundamental quantity.
Answer
(c) First law of thermodynamics is restatement of the principal of conservation of energy as applied to heat energy.
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Question 411 Mark
Assertion : Work done by a gas in isothermal expansion is more than the work done by the gas in the same expansion, adiabatically.
Reason : Temperature remains constant in isothermal expansion and not in adiabatic expansion.
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Question 421 Mark
Assertion : An adiabatic process is an isoentropic process.
Reason : Change in entropy is zero in case of adiabatic process.
Answer
(a) Change in entropy, $\Delta S=\frac{\Delta Q}{T}$. In an adiabatic change, heat transfer $\Delta Q=0 . \therefore \Delta S=0$, or $S=$ constant i.e., entropy remains constant in an adiabatic process, or an adiabatic process is an isoentropic process.
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Question 431 Mark
Assertion : In an adiabatic process, change in internal energy of a gas is equal to work done on or by the gas in the process.
Reason : Temperature of gas remains constant in a adiabatic process.
Answer
(c) In an adiabatic process, no exchange of heat is permissible i.e., $\Delta Q=0$.As, $\Delta Q=\Delta U+\Delta W=0 \Rightarrow \Delta U=-\Delta W$.Also in adiabatic process, temperature of gas changes.
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Question 441 Mark
Assertion : The internal energy of an isothermal process does not change.
Reason : The internal energy of a system depends only on pressure of the system.
Answer
(c) First law of thermodynamics is restatement of the principal of conservation of energy as applied to heat energy.
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Question 451 Mark
Assertion : If an electric fan be switched on in a closed room, the air of the room will be cooled.
Reason : Fan air decrease the temperature of the room.
Answer
(d) If an electric fan is switched on in a closed room, the air will be heated because due to motion of the fan, the speed of air molecules will increase. In fact, we feel cold due to evaporation of our sweat.
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Question 461 Mark
Assertion : lt is not possible for a system, unaided by an external agency to transfer heat from a body at lower temperature to another body at higher temperature.
Reason : According to Clausius statement, "No process is possible whose sole result is the transfer of heat from a cooled object to a hotter object.
Answer
(a) Second law of thermodynamics can be explained with the help of example of refrigerator, as we know that refrigerator, the working substance extracts heat from colder body andrejects a large amount of heat to a hotter body with the help of an external agency i.e., theelectric supply of the refrigerator. No refrigerator can ever work without external supply of electric energy to it.
View full question & answer
Question 471 Mark
Assertion : A room can be cooled by opening the door of a refrigerator in a closed room.
Reason : Heat flows from lower temperature (refrigerator) to higher temperature (room).
Answer
(d) When the door of refrigerator is kept open, heat rejected by the refrigerator to the room will be more than the heat taken by the refrigerator from the room (by an amount equal towork done by the compressor). Therefore, temperature of room will increase and so it will bewarmed gradually. As according to 2- law of thermodynamics, heat cannot be transferred on its own, from a body at lower temperature to another at higher temperature.
View full question & answer
Question 481 Mark
Assertion : The heat supplied to a system is always equal to the increase in its internal energy.
Reason : When a system changes from one thermal equilibrium to another, some heat is absorbed by it.
Answer
(d) According to first law of thermodynamics, $\Delta Q=\Delta U+\Delta W=\Delta U+P \Delta V$. If heat is supplies in such a manner that volume does not change $\Delta V=0$ i.e., isochoric process, then whole of the heat energy supplied to the system will increaseinternal energy only. But, in any other process it is not possible.Also heat may absorbed or evolved when state of thermal equilibrium changes.
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Question 491 Mark
Assertion : Work and heat are two equivalent form of energy.
Reason : Work is the transfer of mechanical energy irrespective of temperature difference, whereas heat is the transfer of thermal energy because of temperature difference only.
Answer
(a) Heat is similar to work in that both represent ways of transferring energy. Neither heat nor work is an intrinsic property of a system, that is, we cannot say that a system contains a certain amount of heat or work.
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Question 501 Mark
Assertion : The specific heat of a gas is an adiabatic process is zero and in an isothermal process is infinite.
Reason : Specific heat of a gas in directly proportional to change of heat in system and inversely proportional to change in temperature.
Answer
(a) $\quad c=\frac{Q}{m \cdot \Delta \theta}$; a gas may be heated by putting pressure, so it can have values for 0 to $\infty$.$C_P$ and $C_V$ are it's two principle specific heats, out of infinite possible values.In adiabatic process $C=0$ and in isothermal process $C=\infty$.
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