CDS (Combined Defence Services) I - General Knowledge Previous Year Question

• 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.

• 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.

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)

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

In a balanced chemical equation, the no of atoms in reactant side are equal to number of atoms in product side.

Step 1- Balance Fe coefficients (a) L.H.S and (c) R.H.S.

Substitute a = 1, c = 2
Step 2- Now balance Carbon coefficients (b) and (d) must be the same 3 on each side.
b = d = 3

So,
a = 1, b = 3, c = 2, d = 3

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.

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

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.

1nm = 10^-9m, or we can say 10^-7cm

• 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.

• 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.

Both the statements are individually true, but Statement II is not the correct explanation of Statement I

Statement 1- Karst topography is formed by the dissolution of soluble rocks like limestone, sandstone, forming underground drainage sinkholes and caves.

Statement 2- These sinkholes may vary in size in depth from a meter to a few hundred meters.

Statement 1 shows the characteristic of Karst and Statement 2 defines sinkhole. Both the statements are individually true, but Statement II is not the correct explanation of Statement I.

Both the statements are individually true, and Statement II is the correct explanation of Statement I

Incised meanders form during the mature stage of the river at which rivers initially started flowing and there were only plain areas and not enough highlands. Now, with the passage of time as Mountains and Plateaus rise, the meandering course of these rivers starts vertical erosion and Incised meanders are formed.

Both the statements are individually true, and Statement II is the correct explanation of Statement I

Statement 1- Glacier troughs tend to have flat valley floors and steep, straight sides depending on the glacier erosion.

Statement 2- A flat floor glacier trough is a result of uniform glacier erosion.

Both the statements are individually true, but Statement II is not the correct explanation of Statement I

Statement 1- Tundra climate is usually found between the 60-75-degree latitude lines. Tundra climate areas experience a very harsh winter with a temperature of about -18 to -50 and a cool summer. As a result, this region has less biodiversity.

Statement 2- During the summer, much of the snow and ice melts and forms soggy marshes and bogs, making condition worse and a less reproductive warm period.

Both the statements are individually true, but Statement II is not the correct explanation of Statement I

Statement 1- Tides are the rise and fall of the levels of the ocean. Tides are caused by the gravitational pull of the Sun and Moon as well as the rotation of the Earth.

Statement 2- The direction of rotation of Earth is from West to East or left to right.

Statement I is false but Statement II is true

Tuberculosis is a communicable disease caused by transferring of bacteria from infected person to a normal person by sneezing or coughing and that do not deal with visiting a crowded place until infected person and bacteria in the air.

Both the statements are individually true but statement 2 is not the correct explanation of statement 1.

Statement 1- Bioaccumulation is the process of accumulation of chemicals in an organism like pesticides, heavy metals and toxic substance that leads to threat to health, life and to environment.

Statement 2- Planktons are primary producer and large fishes are tertiary consumer which consume producers i.e. planktons and other small fishes that result in biomagnification or increase in the concentration of pesticides thus due to intake large fishes of the pond are found to have higher concentration of pesticides than planktons of the same pond.

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

Adipocyte are also known as lipocytes, their primary function is to store fat.

The function of other tissues are as follows

Chondrocytes - produce and maintain the cartilaginous matrix

Osteocyte- maintain strength and health of bone matrix.

Reticulocyte - Red blood cell formation.

The correct organ help in locomotion of the following are as follows

Euglena : Flagellum
Paramecium : Cilia
Nereis : Parapodia
Starfish : Tube Feet

All are mentioned correct except Nereis whose organ is Parapodia.

Lysosomes are formed by the fusion of Golgi network with endosomes, which contain molecules taken up by endocytosis at the plasma membrane. Lysosomes are tiny sack filled with fluid containing digestive enzymes that acts as a biological catalyst. The main function of lysosomes is to remove waste as well as destroying a cell after it has died. They are also known as garbage disposal of cells.

The protein synthesized in the endoplasmic reticulum has to pass 3 double-layered membrane layers to reach inner thylakoid space of chloroplast.

Expansion and compression of air causes adiabatic temperature changes in atmosphere.

As air is heated it becomes less dense and this air parcel moves to upper atmosphere. This air parcel continues to expand resulting in less heat available per unit volume which causes change in atmospheric temperature.

• Collision coalescence process is an important mechanism in formation of raindrops in warmer clouds or we can say whose temperature do not extend beyond the freezing level.
• This phenomenon cannot occur in cirrocumulus clouds because they are made up of ice crystals and supercooled water.

Leh is the place in India that experiences highest atmospheric pressure during winter.

During the winter season, the weather in India is typically influenced by the pressure distribution in the Central and in Western Asia. A high-pressure centre is developed on the Northern side of the Himalayan range and it accounts for the air movement from the Northern side towards the Southern side of the mountain range.

Propounder of given theories are as follows-

Xenon gas is used in photographer’s flashgun

A Xenon flashgun produces an extremely intense full-spectrum white light for a very short duration. It consists of a glass tube filled with xenon gas which emits a short and very bright flash of white light when a high voltage is applied to it.

• A compound is a substance formed when two or more elements chemically bonded together. So, all particles of the compound cannot have the same particles. If it has the same particles, then it will be referred to as an element.
• The elements of compound are chemically combined, so they cannot be separated by simple physical methods.

• Mg (HCO₃)₂ Magnesium Hydrogen Carbonate and Ca (HCO₃)₂ Calcium bicarbonate cause temporary hardness in water.
• Hard water is water that contains cations with a charge of +2, especially Ca²⁺ and Mg²⁺ Hence, both the salts mentioned above impart hardness to water. Hardness of water can be removed by boiling water, ion exchange process, Calgon process, by adding washing soda etc.