Test: Class 8 General Science NCERT Based - 4


30 Questions MCQ Test Science & Technology for UPSC CSE | Test: Class 8 General Science NCERT Based - 4


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This mock test of Test: Class 8 General Science NCERT Based - 4 for UPSC helps you for every UPSC entrance exam. This contains 30 Multiple Choice Questions for UPSC Test: Class 8 General Science NCERT Based - 4 (mcq) to study with solutions a complete question bank. The solved questions answers in this Test: Class 8 General Science NCERT Based - 4 quiz give you a good mix of easy questions and tough questions. UPSC students definitely take this Test: Class 8 General Science NCERT Based - 4 exercise for a better result in the exam. You can find other Test: Class 8 General Science NCERT Based - 4 extra questions, long questions & short questions for UPSC on EduRev as well by searching above.
QUESTION: 1

Consider the following statements about friction.

1. Heat is generated due to friction.

2. Kabaddi players rub dust on their hands, so that friction is increased when they try to grab their opponents.

3. Friction applied by fluids is called drag.

4. Sliding friction is less than static friction.

Which of the statements given above is/are correct?

Solution:
  • Interlocking between two surfaces in contact is the reason behind friction. In the absence of friction, we will be unable to hold a pen or pencil. It is due to friction that a matchstick catches fire on rubbing.

  • Friction causes heat. Kabaddi players rub sand/dust on their hands, which increases friction. Substances which decrease friction are called lubricants. Water and other fluids also apply friction on the objects that move across them.

  • Friction applied by fluids is called ‘drag’. When an object slides over a surface, it applies sliding friction on it. Sliding friction is less than static friction.

QUESTION: 2

Consider the following statements with respect to sound:

1. It can travel through solids, liquids, gases and vacuum.

2. The intensity of sound is measured in decibels (dB).

3. For the human ear, the range of audible frequencies is roughly from 20 Hz to 20,000 Hz.

Which of the statements given above is/are correct?

Solution:
  • Sound cannot travel in vacuum.The intensity of sound is measured in decibels (dB).The number of oscillations per second is called the frequency of oscillation. Frequency is expressed in Hertz.

  • Its symbol is Hz. A frequency of 1 Hz is one oscillation per second. Sounds of frequencies less than about 20 vibrations per second (20 Hz) cannot be detected by the human ear.

  • On the higher side, sounds of frequencies higher than about 20,000 vibrations per second (20 kHz) are also not audible to the human ear. Thus, for the human ear, the range of audible frequencies is roughly from 20 to 20,000 Hz.

QUESTION: 3

Consider the following statements regarding pitch of sound.

1. It depends on the frequency of sound.

2. Birds produce high pitched sound; while the roar of a lion is a low pitched sound.

3. Generally, females have a higher pitched voice than males.

Which of the statements given above is/are correct?

Solution:
  • The intensity of sound depends on the amplitude, and the pitch depends on the frequency. A higher amplitude produces a loud sound, while a smaller amplitude produces a soft sound. Similarly, a higher frequency produces a high pitched sound, and a low frequency produces a low pitched sound.

  • Birds produce high pitched sound; while the roar of a lion is a low pitched sound. This is despite the fact that the sound of a lion is louder while the sound produced by a bird is softer. Similarly, in instruments, A Dhol produces a sound with low frequency, while a whistle produces a sound with high frequency.

QUESTION: 4

Assertion A: Utensils used to store food have a layer of tin electroplated over iron.

Reasoning R: Tin is less reactive than iron.

Choose the correct answer from the options given below:

Solution: Tin utensils used to store food are made by electroplating a layer of tin over iron, because tin is less reactive than iron. Electroplating is the process of applying a layer of a metal over another by the means of electricity.

QUESTION: 5

Assertion A: Iron used to strengthen the bridges and automated vehicles, has a tendency to be easily corroded and rusting.

Reasoning R: To prevent the corrosion and rusting, a layer of zinc is electroplated on iron.

Select the correct answer from the options given below:

Solution:
  • Iron is used to strengthen the bridges and automated vehicles. But, iron has a tendency of corrosion and rusting. Therefore, a layer of zinc is electroplated on the iron.

  • Hence, R is not the explanation for A; rather A is the explanation for R. The process of electroplating is used in a variety of everyday products. For example, some parts of the car, taps in the bathroom, gas burner, rim of the wheel have a layer of chromium on them. This gives them a shiny appearance and prevents corrosion.

QUESTION: 6

Which of the following is/ are correct definition of types of friction?

1. Dry friction resists relative lateral motion of two solid surfaces in contact.

2. Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other.

3. Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces.

Which is/are correct statement (s)?

Solution:
  • Friction is defined as the force that opposes the motion of a solid object over another. There are mainly four types of friction: static friction, sliding friction, rolling friction, and fluid friction.

  • Friction and normal force are directly proportional to the contacting surfaces and it doesn’t depend on the hardness of the contacting surface. With the increase in relative speeds, the sliding friction reduces whereas fluid friction increases with the increase in the relative speed, also fluid friction is dependent on the viscosity of the fluid.

QUESTION: 7

Which of the following is/ are not applications of Ultrasonic Waves?

1. For measuring the depth of the Sea.

2. In sterilizing of a liquid.

3. In Ultrasonography

4. In sterilizing a needle.

Options are:

Solution: Applications of Ultrasonic Waves are: sending signals, for measuring the depth of sea, for cleaning cloths, aeroplanes, machinery parts of clocks, for removing lamp-shoot from the chimney of factories, in sterilizing of liquid and in Ultrasonography.

QUESTION: 8

What will be the effect of temperature on speed of sound?

Solution: The speed of sound increases with the increase of temperature of the medium. The speed of sound in air increases by 0.61 m/s when the temperature is increased by 1C.

QUESTION: 9

A positive charge is moving towards a person. The direction of magnetic field lines will be in

Solution:
QUESTION: 10

What is the unit of loudness?

Solution: The sensation of a sound perceived in an ear is measured by another term called loudness which depends on intensity of sound and sensitiveness of the ear. Unit of loudness is bel. A practical unit of loudness is decibel (dB) which is 1/10th of bel. Another unit of loudness is phon.

QUESTION: 11

Which of the following statements is not correct?

Solution:
  • Like charges repel each other, while unlike charges attract each other.Charge is generated by rubbing objects against each other. It is a convention to call the charge acquired by a glass rod when it is rubbed with silk as positive.

  • The other kind of charge is called negative.When charge moves, electricity is generated.The process of sending the extra charge from a charged object is called earthing.

QUESTION: 12

Consider the following statements regarding lightning:

1. Positive charge accumulated near the surface of the earth and the negative charge accumulated at the lower surface of the clouds combine to generate light and sound of lightning.

2. The process of generation of lightning is called electric discharge. This can occur between two or more clouds; or between the clouds and earth.

3. To protect the buildings from lightning, an object called a lightning conductor is used.

Which of the statements given above is/are correct?

Solution:
  • During the development of a thunderstorm, the air currents move upward while the water droplets move downward.

  • These vigorous movements cause separation of charges. By a process, the positive charges collect near the upper edges of the clouds and the negative charges accumulate near the lower edges.

  • There is accumulation of positive charges near the ground also. When the magnitude of the accumulated charges becomes very large, the air which is normally a poor conductor of electricity, is no longer able to resist their flow. Negative and positive charges meet, producing streaks of bright light and sound. We see streaks as lightning .

  • The process of generation of lightning is called electric discharge. This can occur between two or more clouds; or between the clouds and earth.

  • Lightning Conductor is a device used to protect buildings from the effect of lightning. A metallic rod, taller than the building, is installed in the walls of the building during its construction. One end of the rod is kept out in the air and the other is buried deep in the ground. The rod provides an easy route for the transfer of electric charge to the ground.

QUESTION: 13

The earth is divided into many layers. Which of the following layers is responsible for tremors?

Solution:
  • Faults in the outermost layer of earth cause tremors. This layer is called ‘crust’. The outermost layer of the earth is not in one piece. It is fragmented. Each fragment is called a plate. These plates are in continual motion.

  • When they brush past one another, or one plate goes under another due to collision, they cause disturbance in the earth’s crust. It is this disturbance that shows up as an earthquake on the surface of the earth.

  • The tremors produce waves on the surface of the earth. These are called seismic waves. The waves are recorded by an instrument called the seismograph.

QUESTION: 14

Consider the following statements about earthquakes:

1. Earthquakes are caused by the movement of plates, the boundaries of the plates are the weak zones where earthquakes are more likely to occur. The weak zones are also known as seismic or fault zones.

2. In India, the areas most threatened are Kashmir, Western and Central Himalayas, the whole of North-East, Rann of Kutch, Rajasthan and the Indo – Gangetic Plain. Some areas of South India also fall in the danger zone.

Which of the statements given above is/are correct?

Solution:
  • Earthquakes arise due to the movement of plates. The boundaries of the plates are the weak zones where earthquakes are more likely to occur.

  • The weak zones are also known as seismic or fault zones.In India, the areas most threatened are Kashmir, Western and Central Himalayas, the whole of North-East, Rann of Kutch, Rajasthan and the Indo – Gangetic Plain. Some areas of South India also fall in the danger zone.

QUESTION: 15

Consider the following statements regarding the measurement of the magnitude of the earthquake.

1. The power of an earthquake is expressed in terms of a magnitude on a scale called Richter scale.

2. Richter scale is a linear scale.

3. An increase of 2 in magnitude means 1000 times more destructive energy.

Which of the statements given above is/are correct?

Solution:
  • The power of an earthquake is expressed in terms of a magnitude on a scale called Richter scale. The Richter scale is not linear. It is logarithmic.

  • As it is logarithmic, each measurement from 1 to 10, marked on the Richter scale denotes a ten times amplitude and 32 times the energy on the seismograph. In fact, an increase of 2 in magnitude means 1000 times more destructive energy.

QUESTION: 16

Consider the following statements:

1. Emission of light by objects.

2. Reflection of light by objects.

3. Dispersion of light.

Which of the above is/are related to the phenomenon of seeing objects?

Solution:
  • To be able to see an object, it is necessary for light from the object to reach the eyes. This light can reach the eyes through emission or reflection.Objects which emit light of their own are called luminous objects, while objects which do not emit light are called non luminous.

  • The phenomenon of splitting of white light into its constituent colours is called dispersion. Rainbow is a natural phenomenon caused by dispersion of light. Dispersion is not responsible for the sight of objects.

QUESTION: 17

Which of the following parts of the eye is responsible for its characteristic color?

Solution:
  • Iris is the part of the eye which is responsible for its characteristic colour. The eye has a roughly spherical shape. Outer coat of the eye is white.

  • It is tough so that it can protect the interior of the eye from accidents. Its transparent front part is called cornea. Behind the cornea, we find a dark muscular structure called iris.

  • In the iris, there is a small opening called the pupil. The size of the pupil is controlled by the iris. Behind the pupil of the eye is a lens which is thicker in the centre, called the convex lens. The lens focuses light on the back of the eye, on a layer called retina.

QUESTION: 18

Consider the following statements about retina:

1. Retina contains several nerve cells.

2. The blind spot is present at the junction of the optic nerve and the retina.

3. The impression of an image does not vanish immediately from the retina.

Which of the statements given above is/are correct?

Solution:
  • Retina contains several nerve cells. Sensations felt by the nerve cells are then transmitted to the brain through the optic nerve.

  • There are two kinds of cells (i) cones, which are sensitive to bright light and (ii) rods, which are sensitive to dim light. At the junction of the optic nerve and the retina, there are no sensory cells, so no vision is possible at that spot. This is called the blind spot.

  • The impression of an image does not vanish immediately from the retina. It persists there for about 1/16th of a second. So, if still images of a moving object are flashed on the eye at a rate faster than 16 per second, then the eye perceives this object as moving.

QUESTION: 19

Which of the following is the Braille system associated with?

Solution: The most popular reading and writing system for visually challenged persons is known as Braille. Louis Braille, himself a visually challenged person, developed a system for visually challenged persons and published it in 1821. The Braille system has 63 dot patterns or characters.

QUESTION: 20

Animals have eyes shaped in different ways, and have various specialities. Consider the following statements regarding these specialities:

1. Eyes of a crab are quite small but they enable the crab to look all around him.

2. Butterflies have large eyes that seem to be made up of thousands of little eyes.

3. The Owl has a large cornea and a large pupil to allow more light in its eye.

Which of the statements given above is/are correct?

Solution:
  • Eyes of a crab are quite small but they enable the crab to look all around him. Butterflies have large eyes that seem to be made up of thousands of little eyes. It can see not only the front and the sides but back as well.

  • The owl has a large cornea and a large pupil to allow more light in its eye. Owls can see very well at night but not during the day. Also, it has on its retina a large number of rods and only a few cones. The day birds on the other hand, have more cones and fewer rods.

QUESTION: 21

Consider the following statements regarding the moon.

1. The moon completes one rotation on its axis as it completes one revolution around the Earth.

2. The day on which the whole disc of the moon is visible is known as the full moon day. The time period between two consecutive full moons is a little less than 29 days.

3. Neil Armstrong landed on the moon for the first time followed by Edwin Aldrin.

Which of the statements given above is/are correct?

Solution:
  • The moon completes one rotation on its axis as it completes one revolution around the Earth. The day of the appearance of the full disc of the moon is called full moon day, but the time period between two consecutive full moons is a little more than 29 days. In many calendars, this is the period of a month.

  • The day on which the whole disc of the moon is visible is known as the full moon day. Thereafter, every night the size of the bright part of the moon appears to become thinner and thinner.

  • On the fifteenth day the moon is not visible. This day is known as the new moon day. The next day, only a small portion of the moon appears in the sky. This is known as the crescent moon.

  • Then again the moon grows larger every day. On the fifteenth day once again we get a full view of the moon. On July 21, 1969 the American astronaut Neil Armstrong landed on the moon for the first time followed by Edwin Aldrin.

QUESTION: 22

Consider the following statements regarding the stars.

1. The stars rise from the east after sunset, and set in the west just before sunrise.

2. The distance between stars is expressed in light years.

Which of the statements given above is/are correct?

Solution:
  • Stars are present in the sky during the daytime as well, but cannot be seen due to the glare of the sun. Due to the rotation of the earth from east to west, the stars appear to be rising from the east and setting at west.

  • The distance between stars is expressed in light years. Hence, statement 2 is correct. It is the distance travelled by light in one year. The speed of light is about 300,000 km per second. Thus, the distance of the Sun from the Earth may be said to be about 8 light minutes.

QUESTION: 23

The stars forming a group that has a recognisable shape is called a constellation. Consider the following statements regarding constellations:

1. One of the most famous constellations is Ursa Major, also known as ‘Saptarishi’.

2. Orion is also called The Hunter.

3. Cassiopeia looks like distorted W or M.

Which of the statements given above is/are correct?

Solution:
  • Constellations were devised by ancient people to be able to recognise stars in the sky. The shapes of constellations resemble objects familiar to those people.

  • One of the most famous constellations is Ursa Major, which is also known as the Big Dipper, the Great Bear or the Saptarshi.Orion is one of the most magnificent constellations in the sky.

  • It also has seven or eight bright stars. Orion is also called the Hunter.

  • Cassiopeia looks like distorted W or M.Some constellations like the Saptarishi are not visible from some places of the Southern Hemisphere. All the stars which make up a constellation are not at the same distance. They are just in the same line of sight in the sky.

QUESTION: 24

Match the items of column 1 with column 2 and use the code given below to choose the correct

Solution:
  • The Sun and the celestial bodies which revolve around it form the solar system. It consists of a large number of bodies such as planets, comets, asteroids and meteors.

  • The eight planets in their order of distance from the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The planet mercury is nearest to the Sun. It is the smallest planet of our solar system. It can be observed just before sunrise or just after sunset, near the horizon.

  • Mercury has no satellite of its own. Venus is earth’s nearest planetary neighbor. It is the brightest planet in the night sky. Sometimes Venus appears in the eastern sky before sunrise. Sometimes, it appears in the western sky just after sunset.

  • Therefore it is often called a morning or an evening star. It has no satellite of its own. Rotation of Venus on its axis is somewhat unusual. It rotates from east to west while the Earth rotates from west to east.

  • Jupiter is the largest planet of the solar system. It is so large that about 1300 earths can be placed inside this giant planet. However, the mass of Jupiter is about 318 times that of our Earth.Uranus also rotates from east to west. Uranus has a highly tilted rotation axis. As a result, in its orbital motion it appears to roll on its side.

QUESTION: 25

Consider the following pairs:

1. Earth: Blue

2. Mars: Red

3. Saturn: Yellow

Which of the pairs given above is/are correctly matched with respect to the planets and their colours?

Solution:
  • When viewed from outer space, the light reflected from the water and land on the Earth, makes it appear blue green. Earth has only one satellite, the moon.Mars appears to be red in colour, hence the name, red planet.

  • Mars has two small natural satellites. Saturn appears to be yellowish in color. The rings around Saturn make it the most unique in the solar system. Its density is least amongst all the planets of the solar system, even less than water.

QUESTION: 26

Consider the following statements regarding asteroids, comets and meteors.

1. Asteroids are present between Mars and Jupiter.

2. Comets revolve around the sun in elliptical orbits.

3. Meteors are called shooting stars.

Which of the statements given above is/are correct?

Solution:
  • There is a large gap in between the orbits of Mars and Jupiter. This gap is occupied by a large number of small objects that revolve around the Sun. These are called asteroids.Comets revolve around the Sun in highly elliptical orbits. Their period of revolution round the Sun is usually very long.

  • A comet appears generally as a bright head with a long tail. The length of the tail grows in size as it approaches the sun. The tail of a comet is always directed away from the sun.

  • At night, when the sky is clear and the moon is not there, bright streaks of light in the sky can be seen. These are commonly known as shooting stars, although they are not stars. They are called meteors.

  • A meteor is usually a small object that occasionally enters the earth’s atmosphere. At that time, it had a very high speed. The friction due to the atmosphere heats it up. It glows and evaporates quickly. That is why the bright steak lasts for a very short time.

QUESTION: 27

Match the items of column 1 with column 2, using the code given below.

Solution:
  • Incomplete combustion of fuels release Carbon Monoxide. It is a poisonous gas, which decreases the oxygen carrying capacity of blood.Chlorofluorocarbons, which are used in refrigerators, air conditioners and aerosol sprays, deplete the ozone layer of the atmosphere.

  • After the Montreal protocol, nearly all the countries have started to use less harmful gases in the place of CFCs. Smoke contains oxides of nitrogen which combine with other air pollutants and fog to form smog.

  • Sulphur Dioxide and Nitrogen Dioxide react with the water vapor present in the atmosphere to give sulphuric and nitric acid. This makes the rain acidic and is called acid rain.

QUESTION: 28

Consider the following gases:

1. Carbon Dioxide

2. Nitrous Oxide

3. Methane

4. Water vapour

Which of the above is/are greenhouse gas/gases?

Solution: Carbon dioxide, Nitrous Oxide, Methane and Water vapour, all are greenhouse gases. These gases trap the heat energy and keep the atmosphere warm. This is called the Greenhouse effect. Without them, life would not be possible on the earth, but excessive greenhouse effect has become a problem.

QUESTION: 29

Consider the following statements:

1. The chemical process of the purification of drinking water is called chlorination.

2. To protect the Ganges from pollution, Ganga Action Plan was started in the year 1985.

Which of the statements given above is/are correct?

Solution: The chemical process of the purification of drinking water is called chlorination. Chlorine pellets or bleaching powder is added to the water. Due to increase in pollution levels, life could not survive in many areas of the Ganges. The pollution level is highest in Kanpur of Uttar Pradesh. In 1985, Ganga Action Plan was started to save the river.

QUESTION: 30

Consider the following statements regarding water pollution:

1. Pesticides and weedicides, used to protect the crop pollute the groundwater.

2. Hot water from factories and power plants are also water pollutants.

Which of the statements given above is/are correct?

Solution:
  • Pesticides and weedicides used for the protection of crops, dissolve in water and are washed into water bodies from the fields. They also seep into the ground to pollute groundwater.

  • Excessive quantities of chemicals which get washed from the fields, act as nutrients for algae to flourish. Once these algae die, they serve as food for decomposers like bacteria.

  • A lot of oxygen in the water body gets used up. This results in a decrease in the oxygen level which may kill aquatic organisms. Hot water can also be a pollutant.

  • This is usually water from power plants and industries. It is released into the rivers. It raises the temperature of the waterbody, adversely affecting the animals and plants thriving in it.