Free Some Natural Phenomena 02 Practice Test - 8th Grade
Question 1
Electric sparks due to lightning have the same phenomenon as that of the sparks when one takes off the woollen clothes.
True
False
SOLUTION
Solution : A
When woollen clothes are removed in the dark, a spark and a crackling sound is observed. Benjamin Franklin showed that the lightning and the spark from our clothes are essentially the same phenomena of the static electricity. In both cases, transfer of charges takes place which results in sparks.
Question 2
Lightning is essentially an electric spark.
SOLUTION
Solution : A
Lightning is an electric spark but on a huge scale. Lightning is a sudden electrical discharge that occurs in a thunderstorm. It is caused by the accumulation of charges in the clouds. The process of electric discharge can occur between two or more clouds or between clouds and the Earth.
Question 3
Two inflated balloons are rubbed with a woollen cloth and are brought close to each other. They repel each other because the nature of charge on one balloon is opposite from the other.
True
False
SOLUTION
Solution : B
If the two balloons repel each other, it means that they have acquired the same kind of charge. We know that like charges repel each other and unlike charges attract each other. So, the two inflated balloons repel each other as they have like charges.
Hence, the given statement is false.
Question 4
An inflated balloon is rubbed with a woollen cloth and in another case, a ballpen refill is rubbed with polythene. When the balloon and refill are brought closer, it is observed that they attract each other. What can we understand by this?
Both acquired the same kind of charge.
They acquired the opposite kind of charges.
One of the object is not charged.
SOLUTION
Solution : B
When you rub one material to another, they are charged by friction, also like charges repel and unlike charges attract each other. In the above experiment, the balloon has acquired a kind of charge that is opposite to the charge acquired by the ballpen refill. As unlike charges attract each other, the balloon and the refill developed a force of attraction with each other, so they acquired opposite kind of charges.
Question 5
In an experiment, a charged object attracts another object. What can be understood from this?
The attracted object must be oppositely charged.
The attracted object must be similarly charged.
The attracted object must be uncharged.
The nature of charges can't be predicted.
SOLUTION
Solution : A
When a charged object attracts the other object, it implies that the attracted object is oppositely charged. Attraction takes place between opposite charges i.e. like charges repel and opposite charges attracts each other.
Question 6
When a glass rod rubbed with silk is brought near a charged plastic straw rubbed with polythene there is an attraction between the two. Identify the charge on the plastic straw.
Positive
Negative
Neutral
Can't be predicted
SOLUTION
Solution : B
The charge acquired by a glass rod when it is rubbed with silk is positive.
Like charges repel and unlike charges attract. The straw gets attracted to the glass rod, which necessarily means that the plastic straw acquired negative charge.
Question 7
Two metal balls are suspended as shown in the figure. A glass rod is rubbed with silk to make it charged. Now, both the balls are individually touched with this glass rod. What is the observation noted?
The balls get attracted to each other.
The balls get repelled from each other.
No attraction or repulsion is seen.
SOLUTION
Solution : B
When the glass rod is rubbed with silk, it becomes charged. Now, when both the metal balls touch the glass rod, both balls acquire the same kind of charge as that of the glass rod. As we know that like charges repel each other, these two balls will repel each other.
Question 8
What are the necessary safety measures taken to protect buildings from damage by lightnings?
SOLUTION
Solution : B
A lightning conductor is a device used to protect buildings from the effect of lightning. A metal rod is installed on the roof of the building during its construction such that the upper tip of the rod is higher than the highest point of the building. This rod is connected to the ground with a conducting wire. The rod provides an easy route for the transfer of electric charge to the ground while bypassing the building.
Question 9
What is the name of the scale used to quantify the size of an earthquake?
Richter
Vector
Meter scale
Seismograph
SOLUTION
Solution : A
The power of an earthquake is expressed in terms of a magnitude on a scale called Richter scale. It measures earthquakes with magnitudes ranging from 1 - 10. Destructive earthquakes have magnitudes higher than 7 on the Richter scale.
Question 10
On richter scale, an increase in the magnitude of 4 units means that the destructive amplitude of the earthquake increases by 4 times.
True
False
SOLUTION
Solution : B
Richter scale is not linear. In fact, an increase of 2 in magnitude means 1000 times more destructive energy. For example, an earthquake of magnitude 6 has thousand times more destructive energy than an earthquake of magnitude 4.