Answer: Option B. -> At the bottom
The compressor is the motor (or engine) of the cooling system. It is normally at the bottom of the refrigerator in the back. The compressor runs whenever the refrigerator thermostat calls for cooling.

Answer: Option A. -> Hydrogen
Hydrogen being gaseous has highest entropy.

Answer: Option D. -> None of these
Basically, refrigeration system consists of devices that compress and expand refrigerant gas . When refrigerant gas is compressed it expels heat and when it is suddenly expanded, absorbs heat. A refrigerator (colloquially fridge) is a common household appliance that consists of a thermally insulated compartment and a heat pump (mechanical, electronic, or chemical) that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room. A vapour compression cycle is used in most household refrigerators, refrigerator– freezers and freezers. In this cycle, a circulating refrigerant such as R134a enters a compressor as low-pressure vapour at or slightly above the temperature of the refrigerator interior. The vapour is compressed and exits the compressor as high pressure superheated vapour. The superheated vapour travels under pressure through coils or tubes comprising the condenser, which are passively cooled by exposure to air in the room. The condenser cools the vapour, which liquefies. As the refrigerant leaves the condenser, it is still under pressure but is now only slightly above room temperature. This liquid refrigerant is forced through a metering or throttling device, also known as an expansion valve (essentially a pin-hole sized constriction in the tubing) to an area of much lower pressure.

Answer: Option D. -> Thermodynamics
Thermodynamics is the branch of physics that deals with the relationships between heat and other forms of energy. In particular, it describes how thermal energy is converted to and from other forms of energy and how it affects matter.

Answer: Option C. -> With the speed of light
Heat is a form of energy. An important property of heat is that it flows from a body at higher temperature to another body at lower temperature.

Answer: Option A. -> 210 kN/mm2
The modulus of elasticity for mild steel is approximately equal to 210 kN/mm2.

Answer: Option A. -> Have large coefficient of expansion
Gases are more sensitive to the temperature than liquids (such as mercury). That means gas expands more than the mercury for the same increase of temperature. Hence the gas thermometer is more sensitive than liquid (mercury) thermo-meter.

Answer: Option B. -> The liquid boils
The liquid boils when the vapour pressure equals the atmospheric pressure.

Answer: Option B. -> Decreases
Relative humidity is the ratio of the partial pressure of water vapour in an air-water mixture to the saturated vapour pressure of water at a prescribed temperature. The relative humidity of air depends not only on temperature but also on the pressure of the system of interest. If the system at State A is isobarically heated (heating with no change in system pressure) then the relative humidity of the system decreases because the saturated vapour pressure of water increases with increasing temperature.

Answer: Option A. -> Only proportional region of the stress strain curve
The Hooke's law is valid only when the stress is proportional to the strain, that is only in the proportionality limit.