General Knowledge Practice Questions Set for NDA/CDS & Defence Exams | Set-3|

B. Caesium

• Caesium (Cs-133) is used as timekeeper in atomic clocks.
• Cesium is used because of its high resonant frequency of 9,192,631,770 Hz.
• Atomic clocks are the most accurate timekeeping device with an error of about 1 second in 100 million years.
• They are used to calculate International Atomic Time (IAT), local time around the world and in satellite navigation system.

A. Potassium

• Potassium and Sodium are involved in the control of water content of blood.
• More Sodium and Potassium content results in more water content in blood
• This excess water in blood leads to high blood pressure.

A. Carbon dioxide

The presence of Carbon dioxide in water makes an acidic solution. Carbon dioxide in addition with water forms Carbonic acid (H₂CO₃).

CO₂ + H₂O → H₂CO₃ (Carbonic acid)

C. Magnesium

Magnesium is essential for the formation of chlorophyll. Without Magnesium plants are not able to capture sunlight that is essential for photosynthesis.

The chemical equation for photosynthesis is as follows-

6CO₂ + 6H₂O  C₆H₁₂O₆ + 6O₂

Carbon-di-oxide + Water  Glucose(energy) + Oxygen

A. To increase the life of the bulb

Argon gas is used in electric bulbs to stop the oxygen in the light bulbs from corroding the hot tungsten filament which in result increase the life of a bulb.

D. T = (tc +273.15)

0ºC is equivalent to 273.15K so add 273.15 in Celsius to obtain Kelvin.

D. Wooden hollow pipe placed in vacuum.

Sound wave cannot travel through a wooden hollow pipe placed in vacuum.

Sound energy transfer in form of vibrations, these vibrations need matter to travel, absence of matter in vacuum makes these waves impossible to travel.

C. 1 and 2 only

• Statement 1- For a body to be in equilibrium net force on the object must be zero which results in zero net moment.
• Statement 2- According to Newton’s First Law If a body continues in its state of rest or of uniform motion unless acted upon by an external force. So linear momentum of a body on which no external force acts is conserved.
• Statement 3- In inelastic collision Kinetic energy is transfer from one body to other so kinetic energy always do not remain conserve.So only statement 1 and 2 are correct.

C. 3 and 4 only

• Magnetic and chemical effect of current has no effect on the working of safety fuse.
• Magnitude and heating effect of current are responsible for the working of safety fuse. A fuse has a metal wire or strip with low melting point that melts when too much current flows through it. Melting of which depends on the amount of current passing through which causes heating effect.
• So only option 3 and 4 are correct.

D. Flying fish

Flying fish is a true fish, other are not because they belong to the following phylum