SOLVED PAPER 2021 (CDS) (I) (General Awareness)

Total Questions: 120

101. Which one of the following metals has both malleability and ductility properties ?

Correct Answer: (b) Au
Solution:Luster is basically due to free electron. As we move down the group, the size of the atom increases and more shell are added, so due to screening effect, effective nuclear charge is less and hence electrons are loosely bound. More over the non-metallic property decreases on going from top to the bottom of the group. Therefor iodine is Lustrous.

102. Which one of the following metals has both malleability and ductility properties?

Correct Answer: (b) Au
Solution:Gold (Au) is the most malleable of all metals. It can be drawn into a wire of single-atom width, and then stretched considerably before it breaks.

103. We are given three copper wires of different lengths and different areas of cross-section. Which one of the following would have highest resistivity ?

Correct Answer: (d) All the wires would have same resistivity.
Solution:The correct answer is All the wires would have same resistivity. Resistivity of material depends on the nature of the material. The resistivity of a particular material is measured in units of Ohm-Metres (2 m) which is also affected by temperature.

104. Which of the following statements about 'fission' is correct?

1. It is related with the creation of new individuals by means of cell division in unicellular organism.
2. It is related with 'the transformation of heavier nuclei into smaller nuclei.
3. It is related with the creation of a heavier nuclei by means of combining two higher nuclei.

Select the correct answer using the codes given below:

Correct Answer: (c) 1 and 2
Solution:Fission wheather, it is binary or multiple is a mode of asexual reproduction in which a unicellular organism like Amoeba, Bacteria, etc., divides into two or multiple progenies through cell division. It results in transformation of heavier nuclei of parent into smaller nuclei of progenies.

105. Which one of the following is an electric conductor?

Correct Answer: (c) Human body
Solution:Flow of charges and ions constitute electric current. As our body cells contain various ions like sodium ion, potassium ion, chloride ion, etc. which have the tendency to conduct electricity and this makes our body good conductor of electricity.

106. A non-spherical shining spoon can generally be considered as a

Correct Answer: (b) Parabolic mirror
Solution:The property of a parabolic mirror is that all reflected rays pass through a single point, the focus. On the other hand, the concave side of the spoon acts like a concave mirror. If the spoon is held at arm's length, the object is farther from the reflecting surface than the center of curvature.

107. Who amongst the following is a pioneer in discovering the heating effect of electric current?

Correct Answer: (c) James P. Joule
Solution:James Prescott Joule English physicist who established that the various forms of energy mechanical, electrical and heat are basically the same and can be changed from one into another.

In 1840 that the amount of heat per second that develops in a wire carrying a current is proportional to the electrical resistance of the wire and the square of the current.

He determined that the heat evolved per second is equivalent to the electric power absorbed or the power loss.

P = t²R

108. Which one of the following laws of electromagnetism does not give the direction of magnetic field ?

Correct Answer: (b) Fleming's left-hand rule
Solution:Faraday's law of induction is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force -a phenomenon known as electromagnetic induction.

109. An antibiotic is not useful against a virus whereas a vaccine is. Which one of the following is the most appropriate reason for this ?

Correct Answer: (d) A virus does not use biochemical pathways which can be blocked by an antibiotic. But a vaccine can boost an immune system to fight the virus.
Solution:Antibiotics block various biochemical pathways of a pathogen, i.e. bacteria to inhibit its growth and kill it in process, but virus is a non-living particle which does not have these biochemical pathways and use host cells to perform their replication activities. So, they can't be blocked by antibiotics. Vaccines are designed to induce a protective immune response in the body against the specific viruses represented in the vaccine. When vaccinated the immune system of the body produces a specific response, consisting of specific cells and specific antibodies that fight off the infection when exposure to the virus occurs at a later stage.

110. 'Sleeping sickness' is caused by

Correct Answer: (a) Trypanosoma
Solution:African Trypanosomiasis, also known as "sleeping sickness", is caused by protozoan parasites of the species Trypanosoma brucei. It is transmitted by the tse-tse fly, which is found only in sub-Saharan Africa.