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CBSE Questions for Class 8 Physics Some Natural Phenomena Quiz 2 - MCQExams.com
CBSE
Class 8 Physics
Some Natural Phenomena
Quiz 2
How many seismograph stations are used to locate the epicentre of an earthquake?
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$$4$$
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$$2$$
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$$3$$
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$$9$$
Explanation
Atleast $$3$$ seismograph stations are used to locate the epicentre of an earthquake. We f
ind the distance from each seismograph station to the earthquake epicenter. The interception of the three circles is the epicenter (shown as a red dot in the figure.)
Name the scale on which the destructive energy of an earthquake is measured.
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Temperature scale
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Vector scale
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Richter scale
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Energy scale
Explanation
The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes.
A Richter scale is normally numbered 1-10, though there is no upper limit. Earthquakes measuring 1-2 on the scale happen regularly, and they are so small that people cannot feel them. Earthquakes measuring upwards of 7 are less frequent but very powerful and can cause a lot of destruction.
Option C is correct.
A Seismograph is a device that is used to measure the:
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thunderstorm frequency
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earthquake magnitude
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lightning frequency
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lightning intensity
Explanation
A seismograph is a device that measures and records the seismic waves moving through the earth post an earthquake.
Choose the correct statement.
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'P' waves are slower than 'S' waves.
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Both 'P' and 'S' waves have same speed.
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'S' waves are slower than 'P' waves.
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None of the above.
Explanation
The P waves and the S waves are the waves that travel throughout the planet. The P waves apply force in the direction of propagation whereas the S waves make the medium particle move perpendicular to their direction of motion.
The energy is less easily transmitted in the medium in the case of S waves. So, P waves travel faster.
Option $$C$$ is correct.
What are seismic waves caused by?
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Aerial explosion
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Traffic
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Earthquakes
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Heavy rain
Explanation
Tremors on the earth can be caused when a volcano erupts, or a meteor hits the earth, or an underground nuclear explosion or an earthquake.
The tremors produce waves on the surface of the earth. These are called seismic waves.
The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Should you carry an umbrella?
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Yes
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No
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Ambiguous
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Data insufficient
Explanation
Carrying umbrella is not a good idea at all during thunderstorms.
As a lightning flash travels toward the ground from a nearby cloud, it looks for the tallest object. This is because all the objects attached to the ground acts as ground or earthed objects. So lightning takes the shortest path to travel and thus, falls on the tallest object. If you're holding an umbrella in an area surrounded by taller buildings, it's not so risky. But If you are the only tall object in the place surrounding you, the lightning flash will fall on you.
Thus, carrying umbrella is not a good idea at all during thunderstorms.
A seismograph is also known as:
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Seismogram
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Seismology
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Seismometer
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Seismocity
Explanation
A seismograph, which measures seismic waves, is also known as a seismometer.
A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph.
How do we record seismic waves?
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With the help of an oscilloscope.
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With the help of a seismograph.
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With the help of an anemometer.
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None of the above.
Explanation
A seismograph is a device that is used to record and measure the magnitude of seismic waves created by earthquakes.
Rub an empty ball pen refill on a polythene sheet and hold it on top of small pieces of paper. What will be your observation?
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Pieces of paper are attracted.
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Pieces of paper are repelled.
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Pieces of paper are neither attracted nor repelled.
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Pieces of paper are either attracted or repelled.
Explanation
When refill is rubbed on polythene it acquires small electric charges. Due to presence of these charges, pieces of paper gets attracted.
Fill in the blanks:
During the development of a thunder-storm, the air currents move ________ while the water droplets move _______.
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downward, upward
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upward, downward
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downward, downward
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upward, upward
On which principle does a seismograph work?
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Principle of inertia.
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Principle of conservation of momentum.
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Principle of gravitational force.
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None of the above.
Explanation
Seismograph works on the principle of inertia to measure the depth and force of earthquake. The sudden force of earthquake, makes the scale pointer to move and after the tremor, the pointer comes back to its initial position due to its inertia of rest.
Accumulation of charges causes ________ in the clouds.
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Rain
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Earthquake
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Lightning
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Storm
Explanation
Lighting is caused because of accumulation of electric charges between the clouds.
During a thunderstorm, the air currents move upwards while the water droplets move downward.
These vigorous movements cause the separation of charges. This leads to the positive charges collect near the upper edges of the clouds and the negative charge accumulating near the lower edges of the clouds.
There is an accumulation of positive charges near the ground also.
Negative and positive charges meet, producing streaks of bright light and sound. We see streaks as lightning. The process is known as electric discharge. The process of an electric discharge between different clouds or between clouds and the earth causes lightning.
Seismometers can record motions in ________ directions.
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One
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All
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Opposite
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Same
Explanation
Seismometer devices are located in $$3$$ directions and work on the principle of inertia to catch the motions in all directions.
What will be the nature of charge on the metal paper clip of electroscope when a negatively charged body is brought in contact with it?
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Positive
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Negative
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Partially positive
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None of the above
Explanation
The nature of charge will be negative. When a negatively charged body come in context with uncharged metal paper clip then some amount of negative change will transfer from changed body to metal clip. This phenomenon of change transfer is called Conduction.
Lightning is nothing but ________.
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electric discharge
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electricity
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electro - magnetic discharge
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magnetic effect
Explanation
Lightning is a naturally occurring
electric discharge
during which two electrically charged
regions, both in the atmosphere
or one on the ground, cause a large transfer of electric charge.
This electric discharge happens due
to the large magnitude of the accumulated charges between cloud particles and air. The air can no longer resist their flow and then charges are transferred to the earth or streaks on the ground in the form of lightning.
Fill in the blank:
_________ of charges on surfaces of clouds leads to lightning.
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Accumulation
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Leakage
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Conduction
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Induction
Explanation
The large magnitude of the accumulated charges leads to the meeting of negative and positive charges producing bright light and sound i.e. lightning.
Fill in the blank:
________ charges collect or accumulates near the lower edges of clouds.
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Positive
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Neutral
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Negative
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None of the above
Explanation
The vigorous movements of air current and water droplets causes separation of charges. Negative charges gets accumulated near the lower edges of the clouds.
Fill in the blank:
_______ charges collect near the upper edges of the clouds.
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Negative
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Positive
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Neutral
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No
Explanation
The vigorous movements of air current and water droplets leads to separation of charges.
The positive charges collect near the upper edges of the clouds and the negative charges accumulate near the lower edges.
_________ was the first to discover that lightning is electric discharge.
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Thomas Alva Edison
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Nicolas Tesla
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Benjamin Franklin
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Isaac Newton
Explanation
Benjamin Franklin was the first to show that the lightning is electric discharge which is same as spark out of clothes during winter.
What happens when the end of the paper clip of electroscope is touched by hands?
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Electric current is produced
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Foil strips remain as it is
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Foil strips collapse
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None of the above
Explanation
When the paper clip of electroscope is touched by hands, the foil strips collapse because
the charges on foil strips gets discharged through our body.
What is the frictional order of the following materials on rubbing:
ebonite, glass rod, wool, plastic
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Wool, glass rod, ebonite, plastic
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Glass rod, wool, plastic, ebonite
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Wool, glass rod, plastic, ebonite
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Glass rod, wool, ebonite, plastic
Explanation
When any of these materials are rubbed together, the one in higher order gets positive charge (+) and the one in the lower order gets negative charge (-). The correct frictional order is: glass, wool, ebonite and plastic.
What kind of electric charge is acquired on a glass rod when it is rubbed with silk cloth?
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Positive charge
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Negative charge
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Partially positive charge
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Partially negative charge
Explanation
By convention, glass acquires a higher charge than silk as it losses electron. So, on rubbing, glass acquires a positive charge and silk acquires a negative charge.
When a plastic rod is rubbed with the fur, what charge does the plastic rod get?
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Positive
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Negative
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Neutral
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None of the above
Explanation
Plastic comes below fur in the frictional series of electric charges. So, fur will get positive charge and plastic rod will get the negative charge.
When two bodies are charged by rubbing they acquire:
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equal and opposite charge
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equal and same charge
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negative charge
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positive charge
Explanation
When two bodies are rubbed on one another, they acquire charges equal in amount and opposite in nature.
When a charged body is brought near an electroscope:
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the strips of foils opens up.
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the strips of foils close.
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the strips open and close simultaneously.
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the strips neither open nor close.
Explanation
When a charged body is brought near the top conducting disc of an electroscope, the disc gets induced with charges. These charges run down to the metal strips hanging from the paper clip. Now as both the strips get similar charge, those repel each other and thus open up.
An electroscope is used:
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to detect presence of charge on a body.
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to determine the nature of charge on a body.
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to measure the exact amount of charge on a body.
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for both A and B.
Explanation
Electroscope is a device which is use to detect whether a body is carrying charge and also to detect the nature of charge on the body.
Why does not a steel spoon get charged on rubbing with polythene or woollen cloth?
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Because steel is a poor conductor.
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Because steel is a good conductor.
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Because steel has high density.
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Because a steel spoon is shiny.
Explanation
Steel is a good conductor. As soon as the steel spoon gets charged by rubbing with another object, the electric charge produced on its surface flow through our hand and body into the earth and the spoon remains uncharged.
When plastic comb is used to comb dry hair, which type of charge does the comb acquire?
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Negative
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Positive
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Neutral
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None of the above
Explanation
When we comb our hair, negative charged particles (electrons) leave our hair and travel to the plastic comb. The comb, covered in negatively charged particles, becomes negatively charged as well, and our hair is left with a positive charge.
The device, which can be used to detect whether an object is charged, is:
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telescope
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microscope
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electroscope
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none of the above
Explanation
Electroscope is a device that is used for detection and identification of charge on objects.
When a body gains electrons it acquires
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Positive charge
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Negative charge
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Partially positive charge
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Partially negative charge
Explanation
When the body gains electrons it gets negatively charged, because the number of negative charges are more than the positive charges, so the body becomes negatively charged.
For example: Suppose a chlorine atom in which $$17$$ proton and $$17$$ electrons are present so it is in the neutral state. Now, if this chlorine atom gets one electron then it has total $$17$$ proton and $$18$$ electrons now $$17$$ electrons get neutral but $$1$$ electron remains that makes chlorine to negatively charge.
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