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SSC Junior Engineer 2016

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  • sir plz provide us coal india question paper
  • Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because in Otto cycle

    1. combustion is at constant volume
    2. maximum temperature is higher
    3. expansion and compression are isentropic
    4. heat rejection is lower
  • subar said:

    Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because in Otto cycle

    1. combustion is at constant volume
    2. maximum temperature is higher
    3. expansion and compression are isentropic
    4. heat rejection is lower

    4. heat rejection is lower

    The Otto air standard cycle is more efficient, but in real engine cycles with a gas exchange process, the diesel tends to be more efficient.

    The Otto air standard cycle is more efficient because the area under the PV diagram is larger. This is due to the heat addition being done at constant volume (analogous to the piston being at TDC compression), while the diesel heat addition is at constant pressure, being analagous to the heat being added while the piston is moving down in the expansion stroke. So some of the potential heat energy of the fuel is not fully utilized in the expansion stroke on a diesel.

  • Which of the following is chosen as a standard thermometric substance?

    a. Gas
    b. Thermocouple
    c. Electric resistance
    d. Mercury
  • subar said:

    Which of the following is chosen as a standard thermometric substance?

    a. Gas
    b. Thermocouple
    c. Electric resistance
    d. Mercury

    a. Gas

    When the temperature of a system is measured simultaneously with all the above thermometers which are in options, then it is found that there are considerable variations among the readings. But with experiments, it is found that the minimum variation is observed among the gas thermometers. Therefore gas is chosen as a standard thermometric substance.

    The physical properties of some substances play an important role in the construction of a thermometer as well as to measure the temperature. The physical properties of the materials which changes uniformly with temperature and used for measuring the temperature are called thermometric properties and the materials used for making thermometers are called thermometric substances.

    For example, in a mercury thermometer, the principle of expansion of mercury with rise in temperature is used. The platinum resistance thermometer is based on the principle of the change in resistance with change in temperature.


  • Which of the following is NOT a path function?

    a. Internal energy
    b. Heat energy
    c. Work energy
    d. none of the above
  • subar said:

    Which of the following is NOT a path function?

    a. Internal energy
    b. Heat energy
    c. Work energy
    d. none of the above

    a. Internal energy

    Path functions are properties or quantities whose values depend on the transition of a system from the initial state to the final state. The two most common path functions are heat and work.


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