Solution:

1. Which of the following cannot be charged easily by friction?

(a) A plastic scale

(b) A copper rod

(c) An inflated balloon

(d) A woollen cloth

(b) A copper rod CORRECT

2. When a glass rod is rubbed with a piece of silk cloth the rod

(a) and the cloth both acquire positive charge.

(b) becomes positively charged while the cloth has a negative charge.

(c) and the cloth both acquire negative charge.

(d) becomes negatively charged while the cloth has a positive charge.

(b) becomes positively charged while the cloth has a negative charge. CORRECT

Solution:

(a) Like charges attract each other (T/F)

T

(b) A charged glass rod attract a charged plastic straw (T/F)

T

(c) Lightning conductor cannot protect a building from lightning (T/F)

F

(d) Earthquakes can be predicted in advance (T/F)

F

Solution:

Crackling Sound While Taking Off a Sweater in Winters

When a sweater is taken off during winters, the crackling sound is often heard due to static electricity. This occurs because of the friction between the fabric of the sweater and the body or clothing underneath. The rubbing of these materials causes the transfer of electrons, resulting in an accumulation of electric charge on the surface of the sweater.

As the sweater is removed, the accumulated charge may discharge suddenly, creating a small spark or crackling sound. This phenomenon is known as static discharge. The dry air in winter also prevents the dissipation of the static charge, which is why this sound is more commonly heard in colder months.

Solution:

Explanation: Why a Charged Body Loses Its Charge When Touched with Our Hand

When a charged body is touched with our hand, the charge on the body is transferred to us. This happens because the human body is a good conductor of electricity, and it allows the charge to flow from the charged object to the earth or to the person touching it. The human body is typically at the same electric potential as the ground, so charges from the body spread to the ground when we touch a charged object. This process is known as discharge.

For example, if a body is negatively charged, it has an excess of electrons. When you touch it, some of these electrons transfer to your body. As a result, the charge on the object decreases, and it loses its negative charge, eventually becoming neutral if all excess charge is transferred.

Solution:

Name the scale on which the destructive energy of an earthquake is measured.

The scale used to measure the destructive energy of an earthquake is called the $Richter scale$.

An earthquake measures 3 on this scale. Would it be recorded by a seismograph?

An earthquake measuring 3 on the $Richter scale$ would be recorded by a seismograph, although the tremors would be very weak and may not be felt by people.

Is it likely to cause much damage?

An earthquake measuring 3 on the $Richter scale$ is unlikely to cause much damage as the intensity is low.

Solution:

Three Measures to Protect Ourselves from Lightning

1. Avoid open fields and high ground during a thunderstorm. Seek shelter in a building or a car.

2. Stay away from tall objects like trees, metal poles, and electric wires, as they are more likely to attract lightning.

3. Do not use electrical appliances or telephones with wired connections during a thunderstorm to avoid electrical surges caused by lightning strikes.

Solution:

Explanation: Why a Charged Balloon is Repelled by Another Charged Balloon and an Uncharged Balloon is Attracted by a Charged Balloon

When two balloons are charged, they both acquire like charges (either both positive or both negative). According to the laws of electrostatics, like charges repel each other. Therefore, when two charged balloons are brought near each other, they repel each other due to the mutual repulsion of the like charges. This can be explained by Coulomb's law, which states that the force between two charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

On the other hand, an uncharged balloon does not have any net charge. However, when brought near a charged balloon, the charges in the uncharged balloon get redistributed. This process is called induction. The side of the uncharged balloon closest to the charged balloon will develop an opposite charge (if the charged balloon is positively charged, the uncharged balloon's near side will become negatively charged, and vice versa). The attraction between the oppositely charged regions of the two balloons causes the uncharged balloon to be attracted to the charged one.

Solution:

Instrument to Detect a Charged Body

An instrument that can be used to detect a charged body is called an Electroscope.

An electroscope is a device that detects the presence and magnitude of electric charge. It consists of a metal rod with two thin metal leaves (often made of gold or aluminum) attached at the bottom. The rod is mounted on a non-conducting stand to prevent any loss of charge. When a charged body is brought near the metal knob at the top of the rod, the leaves diverge (move apart), indicating the presence of a charge. The degree of divergence depends on the amount of charge present on the body.

Diagram of an Electroscope

       ____________
      |            |
      |    Knob    |
      |____________|
           |
           |
        (Metal Rod)
           |
    _______|_______
   |               |
   |   Metal Leaves |
   |_______________|

The greater the charge on the object being tested, the more the leaves will spread apart. If the object has the same type of charge as the electroscope, the leaves will repel each other even more. If the charges are opposite, the leaves will still diverge, but to a lesser extent.

Solution:

States in India Where Earthquakes Are More Likely to Strike

• Gujarat
• Assam
• Jammu & Kashmir

Solution:

Precautions to Take During an Earthquake When Outside

1. Stay Away from Buildings, Trees, and Overhead Wires: During an earthquake, it is important to move away from buildings, trees, utility poles, and other structures that may collapse or fall.

2. Drop to the Ground: If you are in an open space, immediately drop to the ground to protect yourself from falling debris or any unexpected shaking.

3. Cover Your Head and Neck: Protect your head and neck by covering them with your arms or any available objects such as a bag or a jacket.

4. Find an Open Area: If possible, move to a clear and open area where there are fewer risks of injury from falling objects or collapsing structures.

5. Stay Calm: Remain calm and avoid panic. Panic can lead to accidents and poor decision-making.

6. Do Not Run: Running during an earthquake can put you at risk of injury. Stay where you are, and wait for the shaking to stop.

Solution:

Would you carry an umbrella if a thunderstorm is predicted? Explain.

If the weather department has predicted a thunderstorm, it is highly likely that there will be heavy rain, strong winds, and lightning. In such conditions, carrying an umbrella would be a wise decision to protect yourself from getting wet due to the rain. However, you should also keep in mind that during a thunderstorm, it is dangerous to stay outside in open areas as lightning could strike. While an umbrella will help keep you dry, it is important to seek shelter in a safe location to avoid lightning strikes.