Assertion (A): A piece of copper and a piece of glass are heated to the same temperature. When touched, thereafter, the copper piece appears hotter than the glass piece.
Reason (R): The density of copper is more than that of glass.
Code:
Correct Answer:
(B)
Both A and R are true but R is not a correct explanation of A
Copper is a very good conductor of heat. So, it allows the maximum amount of heat to pass through it from one point to other. But glass is a poor conductor of heat and hence it allows a very little amount of heat to pass through it. The density of copper is 8920-8960 kg/m3 and the density of glass is equal to 2400-2800 kg/m3. Thus, the density of copper is more than that of glass, but it is not the correct reason of the given assertion. Hence the correct answer is option (b).
Ques:
2
If the temperature of air increases, how would it affect its ability to assume water vapour-
Correct Answer:
(B)
Increase
There is a direct relation between the atmospheric humidity and temperature. The ability of air to assume water vapour depends on its temperature. Thus, if temperature of air is increased then automatically its ability to hold water vapour will also be increased.
Ques:
3
Which of the following statements is NOT true?
Correct Answer:
(B)
Air-Conditioner and Air-Cooler both maintain humidity
Air conditioner and Air-cooler both maintains temperature and the motion of air. But the Air conditioner also having the ability to maintain humidity, while air cooler doesn't have the ability to maintain humidity. Thus, it is clear that option (b) is not true.
Ques:
4
Cooling by AC is done by –
Correct Answer:
(B)
Release of compressed gas
Most of the air conditioners use compressed gas, which can cool the room or other places.
Ques:
5
In which of the following conditions wet clothes will dry earliest?
Correct Answer:
(D)
20% RH, 60oC temperature
The wet clothes will dry earliest at minimum humidity & maximum temperature. Thus, according to options given in the question, option (d) will dry the wet clothes earliest.
Ques:
6
Which one of the following changes occurs when salt is added into the water?
Correct Answer:
(A)
Boiling point is increased and freezing point decreased
If salt is added to water, then the boiling point of water will increase. This happens as the boiling point is the temperature at which the vapor pressure of solvent becomes equal to the external atmospheric pressure. Similarly, it also decreases the freezing point, which in turn will interfere with the frozen solution's crystal structure. That means the temperature will have to be colder to overcome it and freeze the mixture.