The temperature at which the magnetic property of iron disappears (i.e., it becomes nonmagnetic) and its electrical conductivity & specific heat also changes, is called the ‘Curie point’, which is ________________ °C ?

Related Mcqs:

1. With increase in temperature, the electrical conductivity of semiconductors_____________________?

   A. Increases
   B. Decreases
   C. Remain constant
   D. Either A. or B. depends on the type of semi-conductor

2. A solid metallic block weighing 5 kg has an initial temperature of 500°C. 40 kg of water initially at 25°C is contained in a perfectly insulated tank. The metallic block is brought into contact with water. Both of them come to equilibrium. Specific heat of block material is 0.4 kJ.kg-1. K-1. Ignoring the effect of expansion and contraction and also the heat capacity to tank, the total entropy change in kJ.kg-1, K-1 is_________________?

   A. -1.87
   B. 0
   C. 1.26
   D. 3.91

3. Joule-Thomson co-efficient which is defined as, η = (∂T/∂P)H = 1/Cp (∂H/∂T)P, changes sign at a temperature known as inversion temperature. The value of Joule-Thomson co-efficient at inversion temperature is ___________________?

   A. 0
   B. ∞
   C. +ve
   D. -ve

4. The following heat engine produces power of 100,000 kW. The heat engine operates between 800 K and 300 K. It has a thermal efficiency equal to 50% of that of the Carnot engine for the same temperature. The rate at which heat is absorbed from the hot reservoir is____________________?

   A. 100,000 kW
   B. 160,000 kW
   C. 200,000 kW
   D. 320,000 kW

5. Addition of small amount of ________________ to grey cast iron is done to produce nodular grey cast iron ?

   A. Manganese
   B. Phosphorous
   C. Magnesium
   D. Chromium

6. Magnetic permeability of iron is increased by its_____________________?

   A. Decarburising
   B. Alloying with cobalt
   C. Purification
   D. Alternate heating & cooling

7. The amount of heat required to decompose a compound into its elements is _____________ the heat of formation of that compound from its elements?

   A. Less than
   B. More than
   C. Same as
   D. Not related to

8. A gas can be liquefied by pressure alone only, when its temperature is _____________ its critical temperature?

   A. Less than
   B. More than
   C. Equal to or higher than
   D. Less than or equal to

9. If the molar heat capacities (Cp or Cv) of the reactants and products of a chemical reaction are identical, then, with the increase in temperature, the heat of reaction will___________________?

   A. Increase
   B. Decrease
   C. Remain unaltered
   D. Increase or decrease; depends on the particular reaction

10. The wet bulb temperature is lower in dry air than in wet air at the same temperature. A dry bulb thermometer registers a higher temperature than a wet bulb thermometer except at ______________ percent relative humidity ?

    A. 0
    B. 100
    C. 50
    D. None of these