Choose the correct alternative from the following.
Assertion (A) : Increase in carbon dioxide would melt polarice.
Reason (R) : Global temperature would rise.
Answer: A
The Carbon dioxide envelope in earth's atmosphere traps the heat. With increase in the proportion of carbon dioxide, therefore, the global temperature would rise, thus causing the polar ice to melt.
Enter details here
Assertion (A) : Tamil Nadu gets most of the rainfall in winter.
Reason (R) : Tamil Nadu gets rainfall from retreating monsoons.
Answer: A
Rainfall in Tamil Nadu is caused by the retreating monsoons which occur in winter.
Enter details here
Assertion (A) : Graphite is slippery and used as a lubricant.
Reason (R) : Graphite has free electrons.
Answer: B
Graphite possesses a layer structure with two successive layers held by weak forces and able to slide over one another. So, graphite is slippery and this property finds its use as a lubricant.
Enter details here
Assertion (A) : In India, the judiciary is independent of the executive.
Reason (R) : Judiciary favours the government and helps in the implementation of its plans.
Answer: C
In India, the judiciary is completely independent of the executive. It has no interference in the affairs of the state nor can it be influenced by the government.
Enter details here
Assertion (A) : An iron ball floats on mercury but gets immersed in water.
Reason (R) : The specific gravity of iron is more than that of mercury.
Answer: C
Iron with specific gravity less than that of mercury but more than that of water, floats in the former but gets immersed in the second.
Enter details here
Assertion (A) : Copper is used to make electric wires.
Reason (R) : Copper has very low electrical resistance.
Answer: A
A low electrical resistance of copper makes it a good electric conductor. So, it is used to make electric wires.
Enter details here
Assertion (A) : Uranium undergoes nuclear fusion reaction.
Reason (R) : It has a big, unstable nucleus.
Answer: D
Having a big, unstable nucleus, uranium undergoes nuclear fission reaction.
Enter details here
Assertion (A) : A little gap is left between iron rails.
Reason (R) : Iron expands in summer.
Answer: A
Iron expands in summer. So, gaps are left between rails to allow for expansion.
Enter details here
Assertion (A) : When common salt is kept open, it absorbs moisture from the air.
Reason (R) : Common salt contains magnesium chloride.
Answer: A
Magnesium chloride present in common salt is a deliquescent substance i.e., it absorbs moisture from the air the kept in open.
Enter details here
Assertion (A) : When a body is dipped in liquid fully or partially, there is a decrease in weight.
Reason (R) : The decrease in weight is due to the higher density of the displaced liquid.
Answer: C
When a body is dipped in a liquid, there is a decrease in weight due to the upward thrust exerted on its by the water.
Enter details here