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CBSE Questions for Class 8 Physics Some Natural Phenomena Quiz 1 - MCQExams.com
CBSE
Class 8 Physics
Some Natural Phenomena
Quiz 1
The safest place during a thunderstorm is:
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Under a tree
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Near electricity poles
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Inside a car
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Lying on the ground
Explanation
Answer is option C.
A fully-enclosed, all-metal vehicle is very safe, but we should make sure that we do not touch interior metallic areas of a vehicle. The lightning charge goes around the outside of the vehicle, creating a Faraday effect and protecting the occupants inside.
State whether the given statement is True or False :
Earthquakes occur all the time all over the world.
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True
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False
Explanation
The statement is true. Earthquake in less magnitude are not even noticed.
Electroscope is an instrument used to find the quantity of charge on different bodies.
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True
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False
Explanation
Electroscope is an instrument used to measure the amount of charge on a body.
Hence, given statement is $$True$$.
The natural calamity that cannot be predicted accurately in advance:
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Flood
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Cyclone
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Earthquake
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Famine
Explanation
Most earthquakes are caused by the movement of the earth’s plates. While we can determine earthquake-prone areas by studying the movement of the tectonic plates, we still cannot accurately predict when an earthquake might occur.
State whether the given statement is True or False :
Tremors on the Earth can also be caused by the eruption of a volcano.
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True
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False
Explanation
Tremors on the Earth can be caused when a volcano erupts, or a meteor hits the Earth, or an underground nuclear explosion is carried out. However, most earthquakes are caused by the movement of Earth’s plates.
A lightning conductor is made up of:
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copper
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glass
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ebonite
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wood
Explanation
The main attribute common to all lightning rods is that they are all made of conductive materials, such as copper and aluminum. Copper and its alloys are the most common materials used in lightning protection.
A lightning conductor is a metal rod or strap connecting the highest point on a building to the earth. Its purpose is to protect the building from a damaging discharge of electricity between the atmosphere and the building, that is, a lightning strike.
Which of the following is safest way to protect yourself from lightning?
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Run to an open field
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Open an umbrella for cover
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Take shelter under trees
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Squat low on ground
Explanation
Squat low on ground is safest way to protect yourself from lightning as lighting usually discharges through tall structures on the ground.
Suppose you are in a car and it is raining
heavily with thunderstorms. Then what is the best way to protect yourself from a possible thunder-strike?
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To remain in the car
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To get out of the car and take cover under the car
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To run to a nearby tree
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To get out and stand under an electric pole
Explanation
The best way to protect oneself from a possible thunder-strike is to remain in the car with the doors and windows closed. The car touches the earth through the rubber tyres which are insulators. So, the thunder is not attracted by the car as it does not liberate any charge in the air due to insulated connection to the earth.
For all other cases, there are chances of thunder-strike.
A thunderstorm is generally accompanied by:
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Lightning
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Earthquake
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Fire
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Mild breeze
In which of the following states of India, earthquake is most likely to occur?
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Gujarat
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Chhattisgarh
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Tamil Nadu
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Kerala
Explanation
In India, the seismic or fault zones lie below Kashmir, Western and Central Himalays, North-East, Runn of Kutch and Indo-gangetic plane. So, among the options provided, earthquake is most likely to occur in Gujarat.
Magnitude of earthquake is measured in:
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Electroscope
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Richter scale
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Meter scale
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Coulomb
Explanation
The Richter scale measures the magnitude of an earthquake (how powerful it is). It is measured using a machine called a seismometer which produces a seismograph. A Richter scale is normally numbered 1-10, though there is no upper limit.
If earthquake strikes while you are in your bedroom, you should:
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move under the bed.
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sit on the bed.
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stand by the side of the bed.
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jump on the bed.
Explanation
While in bedroom, if earthquake strikes, one should move under the bed. This will help one from surviving from collapsing roof.
During an earthquake, it is always advisable to:
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Stay at the ground floor of a building.
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Move to the top floor of a tall building.
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Stay in open area.
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Stand under a big tree.
Explanation
During an earthquake, it is always advisable to stay in an open area. Taking shelter under a building or a tree may prove very risky as during a high tremor, buildings may collapse and large trees may be uprooted.
The term used to describe a fracture along the earth's crust is
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aftershock
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fault
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focus
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tremor
Explanation
Answer is B.
The fracture along blocks of crust (tectonic plates) is called a fault or fault line.
The weak zones around the boundaries of plates underneath Earth, which are prone to slide and cause earthquake are
commonly known as:
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fault zone
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eruption zone
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explosive zone
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sliding zone
Explanation
The seismic or fault zones, placed around the boundaries of plates underneath Earth, are most prone to slide to cause earthquake.
Lightning occurs because of :
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rain
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electric discharge
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wind
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shaking of earth
Explanation
Answer is B.
Lightning occurs because of electric discharge.
Lightning is one of the most powerful natural forces on the planet. It is a natural discharge of the static electricity built up in storm clouds. Most lightning is formed as a part of thunderstorms. We know from observation of static electricity that static electrical discharges such as lightning are caused by separation of charges into positive and negative ions. Over time more of one charge builds until its natural attraction to the opposite charge causes it to migrate in an electrical discharge.
If a object is charged by contact, it will acquire:
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opposite charge.
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negative charge always.
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same charge as the charged body.
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positive charge always.
Explanation
If an object is charged by contact, it acquires the same charge as the charged object.
The point where seismic waves originate is called the _______ of the earthquake
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centre
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epicenter
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focus
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origin
Explanation
Answer is C.
The point where the waves originate is called the focus of the earthquake.
The point within the earth along the rupturing geological fault where an earthquake originates is called the focus, or hypocenter. The point on the earth's surface directly above the focus is called the epicenter. Earthquake waves begin to radiate out from the focus and subsequently form along the fault rupture. If the focus is near the surface between 0 and 70 km (0 and 40 mi) deepshallow-focus earthquakes are produced. If it is intermediate or deep below the crust between 70 and 700 km (40 and 400 mi) deepa deep-focus earthquake will be produced. Shallow-focus earthquakes tend to be larger, and therefore more damaging, earthquakes. This is because they are closer to the surface where the rocks are stronger and build up more strain.
Match the following and choose the correct answer.
Table A
Table B
a.
Earthquake
1.
Prevent leakage
b.
Lightning
2.
Fault zone
c.
Insulation
3.
Detection of charges
d.
Electroscope
4.
Earthing
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a-2, b-4, c-1, d-3
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a-3, b-4, c-2, d-1
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a-4, b-3, c-2, d-1
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a-1, b-2, c-3, d-4
Explanation
Fault zones are highly prone to earthquakes.
Earthing is done to save buildings from lightning.
Insulation is done on conducting wires to prevent charge leakage.
Electroscopes are used to detect the presence of charges in a body.
So option (A) is correct.
An earthquake is caused by
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shaking of the earth
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strain building up in the tectonic plates
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plates slipping along the fault lines
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None of the above
Explanation
An earthquake is caused by strain building up in the tectonic plates.
Earthquake is shaking of the earth's surface caused by the rapid movement of the earth's rocky outer layer. Earthquakes occur when energy stored within the earth, usually in the form of strain in rocks, suddenly releases. This energy is transmitted to the surface of the earth by seismic waves.
The epicenter is the point inside the earth where
the earthquake originates
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True
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False
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Ambiguous
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Data insufficient
Explanation
Answer is B.
The point within the earth along the rupturing geological fault where an earthquake originates is called the focus, or hypocenter.
The point on the earth's surface directly above the focus is called the epicenter.
Earthquake waves begin to radiate out from the focus and subsequently form along the fault rupture.
Hence, the statement is false.
A seismograph is a scale used for measuring the
magnitudes of earthquakes
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True
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False
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Ambiguous
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Data insufficient
Explanation
A seismograph is an instrument that makes a record of seismic waves caused by an earthquake, explosion, or another Earth-shaking phenomenon. Seismographs are equipped with electromagnetic sensors that translate ground motions into electrical changes, which are processed and recorded by the instruments analog or digital circuits. A record produced by a seismograph on a display screen or paper printout is called a seismogram.
Earthquake is measured by the Richter scale.
A lightning conductor:
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conducts light
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stops lightning
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protect building from the damaging effects of lightning
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none of these
Explanation
The answer is option C.
As a storm cloud approaches, there is a conductive pathway established between the statically charged cloud and the lightning rod. The static charges gradually migrate along this pathway to the ground, thus reducing the likelihood of a sudden and explosive discharge.
Lightning conductors provide a low-resistance path to ground that can be used to conduct the enormous electrical currents when lightning strikes occur. If lightning strikes, the system attempts to carry the harmful electrical current away from the structure and safely to the ground. The system has the ability to handle the enormous electrical current associated with the strike.
Earthquakes can be predicted in advance
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True
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False
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Ambiguous
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Data insufficient
Explanation
Answer is B.
Earthquakes are caused by by shaking of the earth, strain building up in the tectonic plates, plates slipping along the fault lines, etc.
Because we cant get deep enough into the Earth to see what happens before an earthquake happens, therefore we cant predict when its coming.
Although the causes of earthquakes is known, but no instrument could be invented to detect it till now. Hence, earthquakes cannot be predicted in advance.
State whether the given statement is True or False :
Lightning conductor cannot protect a building from lightning.
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True
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False
Explanation
Answer is False.
The use of a lightning rod on a building protects the building by preventing the lightning strike. The idea is based upon the principle that the electric field strength is great around a pointed object. The intense electric fields surrounding a pointed object serve to ionize the surrounding air, thus enhancing its conductive ability.
As a storm cloud approaches, there is a conductive pathway established between the statically charged cloud and the lightning rod. The static charges gradually migrate along this pathway to the ground, thus reducing the likelihood of a sudden and explosive discharge.
The primary role of a lightning rod is to discharge the cloud over a longer length of time, thus preventing the excessive charge buildup that is characteristic of a lightning strike.
Hence, l
ightning conductor is a device to protect a building against lightning.
The adjoining figure shows a negatively charged electroscope. If a negatively charged rod is brought close to, but not touching, the knob, the two leaves will :
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move closer together
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move farther apart
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not move at all
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None of these
Explanation
Answer is B.
In this case, the given electroscope is negatively charged. If a negatively charged rod is brought close to, but not touching, the knob, the two leaves will move far apart as the like charges repel each other.
During earthquakes students should crouch under
their desks
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True
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False
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Ambiguous
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Data insufficient
Explanation
Answer is A.
Getting under a desk or standing in a doorway during an earthquake is a safe way to protect ourselves. This prevents the
hanging wall clocks, photo-frames, water heaters etc., from falling on us in the event of an earthquake.
We should take refuge next to a large sofa or chair when the earth starts moving.
Hence, the statement is true.
Carrying umbrella is not a good idea at all during thunderstorm.
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True
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False
Explanation
Carrying umbrella is not a good idea at all during thunderstorms.
Thunderstorms are electrically charged. Umbrellas mostly contain metal parts which are good conductors of electricity. The electric charge form thunderstorm can move into the umbrella and cause harm to the person carrying it. Therefore, it is nor safe carrying an umbrella during a thunderstorm.
Earthquake and tsunamis are difficult to predict
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True
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False
Explanation
Answer is A.
Earthquakes are caused by shaking of the earth, strain building up in the tectonic plates, plates slipping along the fault lines, etc. and the Tsunamis can also be caused by volcanic eruptions, underwater detonations and even landslides.
Because we cant get deep enough into the Earth to see what happens before an earthquake or tsunami happens, therefore we can't predict when it's coming.
Suppose you are outside your home and an earthquake strikes. What precaution among the following options you should take
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Try to find a clear spot, away from buildings, trees and over head power lines. Drop to the ground.
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If you are in a car or a bus, do not.come out. Ask the driver to drive slowly to a clear spot. Do not come out till the tremors stop.
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Get under a building so that nothing falls on your head.
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Try and move immediately to a place where you would feel it is safe
Explanation
Precautions we should take to protect ourselves when we are outside our home and an earthquake strikes.
1) Try to find a clear spot, away from buildings, trees and over head power lines. Drop to the ground.
(2) If you are in a car or a bus, do not come out. Ask the driver to drive slowly to a clear spot. Do not come out till the tremors stop.
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