General Knowledge Quiz for NDA 2020(NDA & CDS Previous Year Science Questions): 8th Feb 2020

General Knowledge Quiz for NDA 2020(NDA & CDS Previous Year Science Questions): 8th Feb 2020


Jai Hind Aspirants, Defence Adda is providing you all with this quiz on General Knowledge questions for NDA, CDS, AFCAT, CAPF and other Defence Examinations. The questions asked in General Knowlegde Section are based on the topics from History, Polity, Geography, Economics and General Science. We will provide you Important Questions on daily basis so that it becomes easy for you to crack written exam and get call letter for SSB Interview.



Q1.  Which of the following statements about the commonly used automobile battery are true? 
I. It is usually a lead-acid battery. 
II. It has six cells with a potential of 2.1 V each. 
III. Its cells work as galvanic cells while discharging power. 
IV. Its cells work as electrolytic cells while recharging. 
Select the correct answer using the codes given below 

(a) I, II, III and IV
(b) I, II and III
(c) II and IV
(d) III and IV 

Q2. The light emitted by firefly is due to 

(a) radioactive substance
(b) Chemiluminescence process
(c) A photoelectric process
(d) Burning of phosphorus

Q3. Which one of the following polymeric materials is used for making bullet proof jacket?  

(a) Nylon-6,
(b) Rayon
(c) Kevlar
(d) Dacron

Q4. Scuba divers are at risk due to high concentration of dissolved gases while breathing air at high pressure under water. The tanks used by Scuba divers are filled with

(a) Air diluted with helium
(b) O_2
(c) N_2
(d) a mixture of N_2 and helium

Q5. Which one of the following is not needed in a nuclear fission reactor?  

(a) Moderator
(b) Coolant
(c) Accelerator
(d) Control device

Q6. When items or jewellery made of metals such as copper or nickel are placed in a solution having a salt of gold, at thin film of gold is deposited by  

(a) Cooling to below 0°C
(b) Heating above 100°C
(c) Passing an electric current
(d) Just keeping it for 10 min

Q7. Heavy water implies 

(a) Water which is used in heavy industries such as thermal power plants
(b) Water which contains SO_4^(2-) and CI^- of calcium and magnesium
(c) Deuterated water
(d) water which has maximum density

Q8. Which one among the following is a sin smelling agent added to LPG cylinder to help the detection of gas leakage? 

(a) Ethanol
(b) Thioethanol
(c) Methane
(d) Chloroform

Q9. A body is charged negatively. It implies that  

(a) it has lost some of its protons
(b) it has acquired some electrons from outside
(c) it has lost some of its electrons
(d) None of the above

Q10. Which one among the following metals is used for making boats because it does not corrode by sea water?  

(a) Tungsten
(b) Nickel
(c) Antimony
(d) Titanium




Solutions

S1. Ans.(a)
Sol. Automobile batteries are usually lead-acid type, and are made of six galvanic cells in series to provide a 12- volts system. Each cell provides 2.1 volts for a total of 12.6 volts at full charge.
Lead-acid batteries are made up of plates of lead and separate plates of lead dioxide, which are submerged into an electrolyte solution of about 38% sulfuric acid and 62% water. This causes a chemical reaction that releases electrons, allowing them to flow through conductors to produce electricity. As the battery discharges to produce electricity.

S2. Ans.(b)
Sol. Light production in fireflies is due to a type of chemical reaction called bioluminescence. This process occurs in specialized light-emitting organs, usually on a firefly’s lower abdomen. The enzyme luciferase acts on the luciferin, in the presence of magnesium ions, ATP, and oxygen to produce light.

S3. Ans.(c)
Sol. Kevlar, a polymeric material is used for making bullet proof jacket.

S4. Ans.(a)
Sol. The tanks used by Scuba divers are filled with air diluted with helium (i.e., He-O_2 mixture) because unlike nitrogen, helium is not soluble in blood even under high pressure. 

S5. Ans.(c)
Sol. Substances like graphite and heavy water are used as moderator to slow down the speed of neutrons. Cd or B are used as control rods to control rate of fission by absorbing neutrons. Coolant like heavy water or molten sodium is used to carry away the heat.

S6. Ans.(c)
Sol. The process of depositing a thin layer of one metal over the surface of other metal by the process of electrolysis is known as electroplating. Hence, when items or jewelry made of metals such as copper or nickel are placed in a solution having a salt of gold, a thin film of gold is deposited by passing an electric current.

S7. Ans.(c)
Sol. Heavy water or deuterium oxide (D_2 O) is an oxide of deuterium which is an isotope of hydrogen.

S8. Ans.(b)
Sol. Ethyl mercaptan or thioethanol (C_2 H_5 SH) is added during filling of LPG cylinders. It is a strong smelling compound and help in the detection of gas leakage.

S9. Ans.(b)
Sol. Atoms are neutral. When an atom loses electron, it becomes positively charged and when an atom gains electron, it becomes negatively charged and when an atom gains electron, it becomes negatively charged. Hence, a body is charged negatively when it has acquired some electrons from outside.

S10. Ans.(d)
Sol. Titanium (Ti) metal is used for making boats because it does not corrode by the sea water.



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