General Science - MCQ Online Test (3) UPSC MCQs & solutions Free

Ans: d

Explanation: If we go up to height of equal radius of earth then value of g becomes one fourth of the value of g at the earth.

Ans: a

Explanation: If gravity suddenly disappears:

• All bodies will lose their weights.
• We shall be thrown away from the surface of earth due to centrifugal force.
• The motion of the planets around the sun will cease because centripetal force will not be provided.
• Motion of the satellite around earth will also be not possible as no centripetal fore will be provided.

Ans: d

Explanation: Geostationary satellites are stationary with respect to an observer on the earth. Their time period is 24 h and they move with a velocity 3.08 kms. Their height above the surface of earth is 36,000 km. They are always in equatorial plane and their orbits are circular. They are also called parking orbits.

Ans: b

Explantion: If two bulbs, one of 60 W and other of 100 W are connected in series, then the 60 W bulb will glow more, because in series combination current through both the bulbs is the same and the Power consumed P = I2R or P ∞ R. Now, since the resistance of 60 W bulb is more than the resistance of 100 bulb, the 60 W bulb will glow more.

Ans: d

Explanation: When the two mirrors are placed parallel to each other then numbers of images formed are infinite as:

n = (360 / zero) = ∞ (infinite)

Ans: c

Explanation: If the image is erect, formed behind the mirror and enlarged, then the mirror is concave.

Ans: a

Explantion: Concave mirrors are commonly used in torches, search-lights and vehicles headlights to get powerful parallel beams of light.

Ans: a

Explanation: Radar (Radio Detection And Ranging)

• Radar is an object detection system which uses radio waves to determine the range, altitude, direction, or speed of objects.
• It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.
• The radar dish or antenna transmits pulses of radio waves or microwaves which bounce off any object in their path.
• The object returns a tiny part of the wave's energy to a dish or antenna which is usually located at the same site as the transmitter.

Ans: d

Explanation: The audible range of sound for human beings extends from about 20 Hz to 20000 Hz (one Hz = one cycle/s)

Sounds of frequencies below 20 Hz are called infrasonic sound or infrasound.

Frequencies higher than 20 kHz are called ultrasonic sound or ultrasound.

Ans: c

Explanation: Mercury does not wet glass because the cohesive forces within the drops are stronger than the adhesive forces between the drops and glass

Ans: b

Explanation: Latent Heat is defined as the amount of heat absorbed or given out by a body during the change of state. It is of two types:

(1) Latent Heat of Fusion: The latent heat of fusion of a substance is quantity of heat required to change unit mass of solid substance from solid state to liquid state.

The latent heat of fusion of ice is 80 cals.

(2) Latent Heat of Vaporization:

• It is the quantity of heat required to change unit mass of liquid substance from liquid to vapour state while temperature remaining constant.

• The latent heat of vaporization of water is 536 cals.

• Latent heat of vaporization is maximum at 0°C and decreases on increasing temperature.

• Latent heat of vaporization of water decreases on increasing pressure or we may say that the latent heat of vaporization decreases with increase in boiling point.

Ans: b

Explanation:

• A nuclear reactor is a system that contains and controls sustained nuclear chain reactions.

• Reactors are used for generating electricity, moving aircraft carriers and submarines, producing medical isotopes for imaging and cancer treatment, and for conducting research.
• The first nuclear reactor was made by Fermi who used U235 as fuel.
• Hydrogen Bomb is based on the phenomenon of nuclear fusion and was made in 1952 by American scientists.
• The central core of a hydrogen bomb is a uranium (or plutonium) fission bomb which is surrounded by a compound of heavy hydrogen, like lithium hydride (LiH2).
• A fusion bomb is much more destructive than the fission bomb.
• Nuclear Fusion is the phenomenon of fusing of two or more lighter nuclei to form a single heavy nucleus where Mass defect in the process appears as energy.

Ans: d

Explanation: Plasma is the state consists of super energetic and super excited particles. These particles are in the form of ionised gases. The fluorescent tube and neon sign bulbs consist of plasma. Inside neon sign bulb there is neon gas and inside a fluorescent tube there is helium gas or some other gas. The gas gets ionised, that is, gets charged when electrical energy flows through it. This charging up creates a plasma glowing inside the tube or bulb.

The plasma glows with a special colour depending on the nature of gas. The Sun and the stars glow because of the presence of plasma in them. The plasma is created in stars because of very high temperature.

Ans: b

Explanation: Atom is the smallest particle of an element that can take part in a chemical change. It is the smallest particle of an element which does not always exist independently. For example atoms of hydrogen do not exist indecently but instead always occur in pairs. Two atoms of hydrogen form a molecule of hydrogen which exists independently.

Atomicity is the number of atom present in a molecule of an element. Atomicity of hydrogen, oxygen nitrogen and is 2, for ozone it is 3 and phosphorus it is 4.

Ans: d

Explanation: Allotropy is a phenomenon in which an element is found in different forms having different physical properties but similar chemical properties is known as allotropy.

The different forms are called the allotropic or simply allotropes.

Phosphorus, sulphur, carbon etc. are elements which occur in different allotropic forms.

Ans: c

Explanation: Coal- Its common variety is bituminous which is like hard stone and burns with smoky flames. The superior quality coal burns without smoke is called anthracite. It formed out of carbonization of organic and fossil matter buried deep into the earth, under high pressure and high temperature with very-very limited supplies of air, during centuries. Anthracite, bituminous lignite and peat are the types of coal with decreasing Carbon%.

Uses;-

1. It used as a fuel.

2. It is used in the manufacturing of coal gas.

3. The by-product of this process are cock, coal-tar, ammoniac liquor. Coal-tar is a source for making dyes, explosives, chemical etc.

4. It is also used in manufacturing fuel gases like producer gas, water gas and semi water gas.

5. It is used for manufacturing of synthetic petrol by catalytic hydrogenation of coal.

Ans: c

Explanation: Gas carbon and petroleum coke: Gas carbon is produced by scrapping the carbon from the walls of the retort formed as result of destructive distillation of coal. When distillation of crude petroleum is done in a retort, the petroleum coke is deposited on the walls of the retort.

Uses: It is used for making electrode when pressed into sticks, as both are good conductor of electricity.

Sugar charcoal: It is the poorest form of carbon.

1. It can be liquefied even to room temperature but under high pressure.

2. Further, it can be converted into a solid state, known as dry ice which is used as mobile refrigerant.

Carbon-14 is a useful radioactive isotope for tracker studies in organic and bio-chemical system , including the determination of the age of material that were once alive.

The identity and amount of many elements present in trace amount in mixture may be determined by neutron activation anilines. The procedure involves the conversion of nonradioactive isotope of chemical elements and determination of the type and intensity of the radioactivity that results.

Ans: d

Explanation: Gas carbon and petroleum coke: Gas carbon is produced by scrapping the carbon from the walls of the retort formed as result of destructive distillation of coal. When distillation of crude petroleum is done in a retort, the petroleum coke is deposited on the walls of the retort.

Uses: It is used for making electrode when pressed into sticks, as both are good conductor of electricity.

Sugar charcoal: It is the poorest form of carbon.

1. It can be liquefied even to room temperature but under high pressure.

2. Further, it can be converted into a solid state, known as dry ice which is used as mobile refrigerant.

Carbon-14 is a useful radioactive isotope for tracker studies in organic and bio-chemical system , including the determination of the age of material that were once alive.

The identity and amount of many elements present in trace amount in mixture may be determined by neutron activation anilines. The procedure involves the conversion of nonradioactive isotope of chemical elements and determination of the type and intensity of the radioactivity that results.

Ans: b

Explanation: Washing soda is a chemical that can be obtained from sodium chloride is washing soda. Sodium carbonate can be obtained by heating baking soda; recrystallisation of sodium carbonate gives washing soda. It is also a basic salt.

Uses of washing soda

(i) Sodium carbonate (washing soda) is used in glass, soap and paper industries.

(ii) It is used in the manufacture of sodium compounds such as borax.

(iii) Sodium carbonate can be used as a cleaning agent for domestic purposes.

(iv) It is used for removing permanent hardness of water

Ans: c

Explanation: A scale for measuring hydrogen ion concentration in a solution, called pH scale has been developed. The pH of a neutral solution is 7. Values less than 7 on the pH scale represent an acidic solution. As the pH value increases from 7 to 14, it represents an increase in OH– ion concentration in the solution, that is, increase in the strength of alkali.

Tooth decay starts when the pH of the mouth is lower than 5.5.

Bee-sting leaves an acid which causes pain and irritation. Stinging hair of nettle leaves inject methanoic acid causing burning pain.

Ans: d

Explanation:

• A colloid is a heterogeneous mixture.
• The size of particles of a colloid is too small to be individually seen by naked eyes.
• Colloids are big enough to scatter a beam of light passing through it and make its path visible.
• They do not settle down when left undisturbed, that is, a colloid is quite stable.
• They cannot be separated from the mixture by the process of filtration. But, a special technique of separation known as centrifugation can be used to separate the colloidal particles.