Assertion:  The Carnot cycle is useful in understanding

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 Multiple Choice QuestionsMultiple Choice Questions

161.

A certain gas is taken to the five states represented by dots in the graph. The plotted lines are isotherms. Order of the most portable speed νp of the molecules at these five states is

  • νp at 3  > νp at 1 = νp at 2 > νp at 4 = νp at 5

  • νp at 1 > νp at 2 =  νp at 3 > νp at 4 > νp at 5

  • νp at 3 > νp at 2 = νp at 4 > νp at 1 = νp at 5

  • insufficient information to predict the result


162.

Two heater wires, made of the same material and having the same length and the same radius, are first connected in series and then in parallel to a constant potential difference. If the rates of I heat produced in the two cases are Hs  and  HP respectively, then  Hs/HP  will be

  • 1/2

  • 2

  • 1/4

  • 4


163.

In an adiabatic change , the pressure and temperature of a monoatomic gas are relted as P ∝ TC, where C equals

  • 23

  • 52

  • 35

  • 53


164.

Assertion: Ferro magnetic substances become paramagnetic above Curie temperature.

Reason: Domains are destroyed at high temperature.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


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165.

Assertion:  In free expansion of an ideal gas, the entropy increases. 

Reason:  Entropy increases in all natural processes.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


166.

By sucking through a straw, a student can reduce the pressure in his lungs to 750 mm of Hg ( densiy = 13.6 g/cm3). Using the straw, he can drink water from a glass upto a maximum depth of

  • 10 cm

  • 75 cm

  • 13.6 cm

  • 1.36 cm


167.

When you make ice cubes, the entropy of water

  • does not change

  • increase

  • decreases

  • may either increase or decrease depending on the process used


168.

A bimetallic strip consists of metals X and Y. It is mounted rigidly at the base as shown. The metal X has a higher coefficient of expansion compared to that for metal Y. When the bimetallic strip is placed in a cold bath

  • it will bend towards the right

  • it will bend towards the left

  • it will not bend but shrink

  • it will neither bend or shrink


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169.

Assertion:  In an isolated system the entropy increases. 

Reason: The processes in an isolated system are adiabatic.

  • If both assertion and reason are true and reason is the correct explanation of the assertion

  • If both assertion and reason are true but reason is not the correct explanation of the assertion

  • If assertion is true, but reason is false

  • Both assertion and reason are false statements


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170.

Assertion:  The Carnot cycle is useful in understanding the performance of heat engines. 

Reason:  The Carnot cycle provides a way of determining the maximum possible efficiency achievable with reservoirs of given temperatures.

  • If both assertion and reason are true and reason is the correct explanation of the assertion

  • If both assertion and reason are true but reason is not the correct explanation of the assertion

  • If assertion is true, but reason is false

  • Both assertion and reason are false statements


A.

If both assertion and reason are true and reason is the correct explanation of the assertion

A heat engine, or  more  simply  an engine is  a device  that extracts energy from an environment in the form of heat and does useful work.  We choose to study real engines by analyzing  the behaviour of ideal engines. A particular ideal engine called a Carnot engine serves as ideal heat engine. This ideal  engine, turns out to be the best at using energy as heat to do useful work. Carnot engine comprises four cycles. During each cycle  QH as heat from a thermal reservoir at constant temperature  TH and discharges energy  QL  as  heat to a second thermal reservoir at  a  constant lower temperature TL. Thus, Carnot cycle provides a way of determining the maximum possible  efficiency  achievable  with  reservoirs of given temperature. Hence option (a) is true.


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