Class XI

A body cools from 80 ∘∘C to 50 ∘∘C in 5 minutes. Calculate the time it takes to cool from 60 ∘∘C to 30 ∘∘C. The temperature of the surroundings is 20 ∘∘C.
  1. 6 min
  2. 12 min
  3. 15 min
  4. 9 min
The electrical resistance in ohms of a certain thermometer varies with temperature according to the approximate law : R = Roo [1 + αα (T – Too )] The resistance is 101.6 ΩΩ at the triple-point of water 273.16 K, and 165.5 ΩΩ at the normal melting point of lead (600.5 K). What is the temperature when the resistance is 123.4 ΩΩ?
  1. 384.8 K
  2. 364.8 K
  3. 404.8 K
  4. 344.8 K
The latent heat of vaporization (Lv)(Lv) is.
  1. the heat per unit mass required to change a substance from liquid to the vapor state at high pressure and low temperature
  2. the heat per unit mass required to change a substance from vapor to the liquid state without change in the temperature and pressure
  3. the heat per unit mass required to change a substance from liquid to the vapor state , at high temperature and low pressure
  4. the heat per unit mass required to change a substance from liquid to the vapor state without change in the temperature and pressure
The height of mercury column in a simple barometer is h. As tube is inclined to the vertical at an angle ∝∝ the length of the mercury column along the length of the tube is l, then
  1. l = h/cos∝
  2. l = h cos∝
  3. l = h sin∝
  4. 1
A cylindrical vessel is filled with equal mass of mercury and water. The over all height of the two layers is 43.8 cm. Relative density of mercury is 13.6. Then the pressure of the liquid on the bottom of the vessel is
  1. 3 cm of Hg
  2. 16.6 cm of Hg
  3. 1.5 cm of Hg
  4. 6 cm of Hg
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