Practice MCQ Questions and answers on Physics-GK

Supercooling is the process of chilling a liquid below its freezing point, without it becoming solid. A liquid below its freezing point will crystallize in the presence of a seed crystal or nucleus around which a crystal structure can form.

Ferromagnetic materials are mainly solid materials (eg. Iron, cobalt, nickel etc). And this property of ferromagnetism is only observed in the solid materials but not in the liquid or gaseous materials.

In the late of 17th century British scientist Isaac Newton studied cooling of bodies. Experiments showed that the cooling rate is approximately proportional to the difference of temperatures between the heated body and the environment. This fact can be written as the differential relation : dQ dt A T T S= abg, where A is the surface area of the body through which the heat is transferred, T is the temperature of the body, TS is the temperature of the surrounding environment, á is the heat transfer coefficient depending on the geometry of the body, state of the surface, heat transfer mode, and other factors. Surface area or volume ratio is an important influence on temperature control. For same volume sphere has minimum surface area, while circular plate has maximum surface area. So sphere cools slowest and plate cools fastest.

The humidity of the air depends upon weather, temperature and location.

Aluminium being a good conductor of heat conducts away the heat from the substance quite easily and causes quick freezing.

A four-stroke engine (also known as four-cycle) is an internal combustion engine in which the piston completes four separate strokes—intake, compression, power, and exhaust—during two separate revolutions of the engine’s crankshaft, and one single thermodynamic cycle. The earliest of these to be developed is the Otto cycle engine developed in 1876 by Nikolaus August Otto in Cologne, Germany, after the operation principle described by Alphonse Beau de Rochas in 1861.

Spring balance works on the principle of Hooke's law. Hooke's law states that the strain of the material is proportional to the applied stress within the elastic limit of that material.

Assuming the disc is uniform and isotropic (the same in different directions), the hole will expand in the same ratio as the metal. It is because the thermal expansion equation applies to all lengths associated with the metal, including the circumference of the hole, since the edge of the hole is made out of metal. And if the circumference of the hole expands, so does the diameter.

Air is said to be saturated when the amount of water vapour in the air is the maximum possible at an existing temperature and pressure. Air is said to be saturated at 100 percent relative humidity when it contains the maximum amount of moisture possible at that specific temperature.

Charles's law, or the law of volumes, was found in 1787 by Jacques Charles. It states that, for a given mass of an ideal gas at constant pressure, the volume is directly proportional to its absolute temperature, assuming in a closed system.