Maharashtra Board Class 7 Science Chapter 8 Static Electricity Solutions

Exercise 1. Choose The Correct Option In The Blanks.And Fill

Question a. There is between like charges.
Answer: always repulsion
In simple words: Like charges, such as two positive charges or two negative charges, always push each other away.

🎯 Exam Tip: Understanding the fundamental principle of repulsion between like charges is crucial for explaining basic electrostatic phenomena.

Question b. is responsible for generation of electric charge in an object.
Answer: displacement of negative charge
In simple words: Electric charge develops when negative charges (electrons) move from one object to another, creating an imbalance.

🎯 Exam Tip: Focus on electron movement as the primary cause of charge generation, not positive charge displacement, for accuracy in explanations.

Question c. A lightning conductor is made of a - strip.
Answer: copper
In simple words: Lightning conductors are made from copper because it is an excellent conductor of electricity, safely guiding lightning currents to the ground.

🎯 Exam Tip: Remember that good conductivity is key for lightning conductors to function effectively, making copper an ideal material.

Question d. does not get electrically charged easily by rubbing.
Answer: Steel
In simple words: Steel is a good conductor, so any charge generated by rubbing quickly dissipates, preventing easy accumulation of static electricity.

🎯 Exam Tip: Differentiate between conductors and insulators; conductors like steel do not easily hold static charge, while insulators do.

Question e. There is when opposite electric charges come near each other.
Answer: always attraction
In simple words: Opposite electric charges, like positive and negative, naturally pull towards each other.

🎯 Exam Tip: The principle of attraction between unlike charges is fundamental to understanding many electrostatic interactions, including bonding.

Question f. A can be detected with an electroscope.
Answer: charged object
In simple words: An electroscope is a device specifically designed to detect the presence of an electric charge on an object.

🎯 Exam Tip: Knowing the function of an electroscope – detecting charge – is important for questions related to static electricity experiments.

Exercise 2. Explain Why It Is Not Safe To Go Out With An Umbrella When There Is Heavy Raine Lightning Or Thunder.

Question a. Explain why it is not safe to go out with an umbrella when there is heavy raine lightning or thunder.
Answer: Large amount of charges get built up in the clouds in rainy and stormy weather.
1. Sometimes these charges are transferred to the earth in the form of a bolt of lightning.
2. Wire of umbrella is made up of metal and cloth is made up of synthetic material.
3. If lightning strikes, then umbrella catches it and there are chances of fire and it would be dangerous.
4. So it is not safe to go out with an umbrella when there is heavy rain.
In simple words: During a thunderstorm, lightning can strike metal objects. An umbrella often contains metal, making it a potential conductor and increasing your risk of being struck by lightning, which is very dangerous.

🎯 Exam Tip: Highlight the conductive nature of an umbrella's metal parts and the danger of direct lightning strikes during storms for a complete answer.

Exercise 3. Answer In Your Own Words.

Question a. How will you protect yourself from lightning?
Answer: 1. To protect from the lightning, we have to put lightning conductor on high rise buildings,
2. we should not stand under a tree in rainy and stormy weather.
3. We should not go out with an umbrella in heavy rain, lightning or thunder.
In simple words: To stay safe from lightning, avoid open spaces, tall objects like trees, and metal objects like umbrellas during a storm; instead, seek shelter in a sturdy building.

🎯 Exam Tip: List practical safety measures, emphasizing avoiding conductors and seeking enclosed shelter, which are key for protection during lightning.

Question b. How are charges generated?
Answer: 1. Friction causes a charge to develop, because on rubbing, some negative particles are transferred from one substance to the other and the later develops a negative charge.
2. The substance from which particles are removed lose negative charge and hence, it develops a positive charge.
In simple words: Charges are generated by friction when two different materials rub together, causing electrons to transfer from one object to the other, creating a positive charge on one and a negative charge on the other.

🎯 Exam Tip: The core concept here is the transfer of electrons due to friction, leading to an imbalance of charge; clearly state this mechanism.

Question c. In the lightning conductor, what provision is made for spreading the electricity into the ground?
Answer: 1. The lightning conductor, consists of a long copper strip with one end forked. This end is ' at the highest part of the building.
2. The other end of the strip is connected to a plate of cast iron.
3. A pit is dug in the ground, coal and salt are filled into the pit and the iron plate is placed upright in the pit.
4. There is also a provision for pouring water into it.
5. This helps to spread the electric charge quickly into the ground.
In simple words: Lightning conductors have a buried metal plate surrounded by coal, salt, and water to increase ground contact and conductivity, ensuring that the electric charge from lightning safely disperses into the earth.

🎯 Exam Tip: Detail the components (copper strip, iron plate, coal, salt, water) and their role in creating a low-resistance path to effectively disperse lightning charge.

Question d. Why do farmers stick an iron staff into the ground while working in the field in rainy conditions?
Answer: 1. Large amount of charges get built up in the clouds in rainy and stormy weather.
2. Sometimes these charges are transferred to the earth in the form of a bolt of lightning.
3. Due to iron staff, the charges will be conducted to the earth through iron metal and spread quickly into the ground.
4. This way farmers are saved from lighting strike.
In simple words: Farmers stick an iron staff into the ground during storms to act as a personal lightning rod, grounding any nearby electric charges and diverting them away from their bodies, thus protecting themselves from a lightning strike.

🎯 Exam Tip: Explain the iron staff's function as a temporary grounding conductor to protect against lightning by diverting charge, emphasizing personal safety.

Question e. Why is lightning not seen every day during the rainy season?
Answer: 1. When air and clouds rub against each other in the sky the upper part of some clouds becomes positively charged and the lower side become negatively charged.
2. When this negative charge at the bottom of the cloud becomes much larger than the charge on the ground, it starts flowing towards the ground in stages, but this doesn't happen every day. So lightning is not seen every day during the rainy season.
In simple words: Lightning requires a significant buildup of charge difference between clouds or between clouds and the ground, which doesn't occur every day during the rainy season; specific atmospheric conditions are needed for such large-scale charge separation and discharge.

🎯 Exam Tip: Focus on the condition of "significant charge buildup" as the prerequisite for lightning, explaining why it's not a daily occurrence.

Exercise 4. What Are The Characteristics Of A Static Electric Charge?

Question a. What are the characteristics of a static electric charge?
Answer: Following are the characteristics of a static electric charge.
1. The electric charge generated by friction is called frictional electricity. This charge is produced only at the place of friction, hence it is called static electricity.
2. It remains on the object for a short duration.
3. The charges of static electricity are absorbed in moist air.
4. An electrically charged object attracts another object which has no electric charge.
5. Like charges repel each other.
6. Unlike charges attract each other.
7. Repulsion is the sure test of the existence of a static charge.
In simple words: Static electric charges are created by friction, temporary, absorbed by moisture, attract neutral objects, and follow the rule that like charges repel while unlike charges attract, with repulsion being the definitive test for charge.

🎯 Exam Tip: When listing characteristics, ensure to include how static charge is generated, its temporary nature, its interaction with moisture and other objects, and the key principles of attraction and repulsion.

Exercise 5. What Is The Damage Caused By Lightning? How Will You Ereate Awareness To Prevent It?

Question a. What is the damage caused by lightning? How will you ereate awareness to prevent it?
Answer: Due to lightning great damage can occur.
1. It may cause fire.
2. Person on whom lightning strikes may die also.
3. It causes more temperature than sun.
Awareness to prevent it:
1. Guide the people to install lightning conductor on tall buildings.
2. Do not stand on open ground, below a tree, or on a high location during the thunder storms.
3. Do not use plugged in electrical appliances.
4. Do not stand near an electric pole, telephone pole or a tower.
5. Stay in pucca house made of brick and cement.
6. Stand on only wood, a plastic sheet or sack of jute.
In simple words: Lightning can cause severe damage like fires, electrocution leading to death, and extreme heat. To create awareness, educate people about installing lightning conductors, avoiding open areas, trees, and electronic devices during storms, and seeking shelter in sturdy buildings.

🎯 Exam Tip: Clearly categorize your answer into "damage caused" and "awareness/prevention," providing specific examples for each to demonstrate a comprehensive understanding.

Project:

Question a. Make an electroscope yourself by using a thin aluminium foil and check which substances become electrically charged.
Answer: (This is a practical activity. No specific text answer is provided. Students are expected to perform the experiment.)
In simple words: An electroscope can be made with aluminum foil to test different materials for their ability to acquire an electric charge when rubbed, by observing the foil leaves' movement.

🎯 Exam Tip: For practical-based questions, describe the experimental setup and the expected observation (e.g., divergence of leaves) to demonstrate understanding of the concept.

Exercise 1. Choose The Correct Option And Fill In The Blanks.

Question 1. named the electric charges as positive charge and negative charge.
Answer: Benjamin Franklin
In simple words: Benjamin Franklin was the scientist who first categorized electric charges as positive and negative.

🎯 Exam Tip: Remembering key historical figures like Benjamin Franklin and their contributions helps connect concepts to their scientific origins.

Question 2. Each atom contains a stationary charge and moving charges.
Answer: positive, negative
In simple words: Every atom has a stationary positive charge (protons in the nucleus) and moving negative charges (electrons orbiting the nucleus).

🎯 Exam Tip: Distinguish between the stationary positive charge (nucleus) and the mobile negative charge (electrons) within an atom.

Question 3. Each atom is electrically .
Answer: neutral
In simple words: Ordinarily, an atom is electrically neutral because it has an equal number of positive protons and negative electrons, balancing out the charges.

🎯 Exam Tip: The electrical neutrality of an atom is a fundamental concept; ensure you link it to the equal count of protons and electrons.

Question 4. Amber is called in the Greek language.
Answer: electron
In simple words: The Greek word for amber is 'elektron', from which the term 'electricity' originated, as amber was historically observed to attract light objects after being rubbed.

🎯 Exam Tip: Knowing the etymology of "electron" from "amber" provides a good historical context for understanding the discovery of electricity.

Question 5. The charges of electricity are absorbed in moist air.
Answer: static
In simple words: Static electric charges tend to dissipate or be absorbed more readily in moist air because water molecules can conduct and neutralize the charges.

🎯 Exam Tip: Remember that humidity can significantly affect static electricity experiments, as moist air helps conduct away accumulated charges.

Question 6. Electrically charged objects uncharged objects.
Answer: attract
In simple words: An electrically charged object will attract an uncharged object due to induction, where the charged object causes a temporary charge separation in the neutral object, leading to an attractive force.

🎯 Exam Tip: This is a crucial concept: charged objects attract neutral objects, which is different from attraction between oppositely charged objects. Ensure you understand the distinction.

Question 7. is used as a test for identifying an electrically charged object.
Answer: Repulsion
In simple words: Repulsion is the definitive test to confirm if an object is electrically charged because attraction can occur between a charged and an uncharged object.

🎯 Exam Tip: Emphasize that *repulsion* proves an object is charged, not attraction, as attraction can also happen with neutral objects due to induction.

Question 8. The property of amber to attract things was named electricity by in 1646 AD.
Answer: Thomas Brown
In simple words: Thomas Brown coined the term "electricity" in 1646 AD, inspired by the ancient Greek observations of amber's attractive properties when rubbed.

🎯 Exam Tip: Note Thomas Brown's contribution to naming the phenomenon of electricity, which is an important historical fact.

Question 9. The electric charge generated by stays only as long as the charged object is near to it.
Answer: induction
In simple words: The electric charge developed on an object by induction is temporary and exists only as long as the inducing charged object remains nearby.

🎯 Exam Tip: Clearly define induction as the process where charge is created *temporarily* in an object due to the proximity of another charged object, without direct contact.

Question 10. A simple device is used to detect the electric charge on an object.
Answer: gold leaf electroscope
In simple words: A gold leaf electroscope is a simple and sensitive instrument used to detect the presence and approximate magnitude of an electric charge on an object.

🎯 Exam Tip: Understand the primary function of a gold leaf electroscope: detecting electric charge, making it a key tool in electrostatics.

Question 11. Lightning is a form of .
Answer: electric charge
In simple words: Lightning is a massive, rapid discharge of static electric charge that builds up in thunderclouds.

🎯 Exam Tip: Define lightning as an electrical discharge, linking it directly to the concept of static electric charge for a concise answer.

Question 12. The gas protects us from the harmful ultra violet rays coming from the sun.
Answer: ozone
In simple words: The ozone layer in the Earth's atmosphere absorbs most of the Sun's harmful ultraviolet (UV) radiation, protecting life on Earth.

🎯 Exam Tip: Recognize the vital role of ozone in protecting Earth from UV radiation, a concept often linked with atmospheric electricity or lightning's effects.

Question 13. The is a device used for protection from a lightning strike.
Answer: lightning conductor
In simple words: A lightning conductor is a metal rod or strip installed on buildings to safely divert lightning strikes into the ground, protecting the structure.

🎯 Exam Tip: Know the purpose of a lightning conductor: to provide a safe path for lightning current to the ground, preventing damage to buildings.

Question 14. Due to the energy of the lightning, the oxygen in the air is converted into .
Answer: ozone
In simple words: The intense energy from a lightning strike can split oxygen molecules (O2), allowing them to recombine into ozone molecules (O3).

🎯 Exam Tip: This is a specific chemical effect of lightning; remember that it facilitates the conversion of atmospheric oxygen into ozone.

Exercise 2. Match The Columns:

Question a.

Answer:

In simple words: This matching exercise reinforces core concepts: like charges repel, unlike charges attract, copper strips are used in lightning conductors, and gold leaves are components of an electroscope.

🎯 Exam Tip: For matching questions, ensure you understand the direct relationship between each pair of items; this shows conceptual clarity.

Exercise Say Whether True Or False, Correct And Rewrite The False Statement:

Question 1. Charges cannot be transferred from one body to another.
Answer: False. Charges can be transferred from one body to another
In simple words: Electric charges can indeed be transferred between objects, for example, through rubbing (friction), contact, or induction.

🎯 Exam Tip: Highlight the mechanisms of charge transfer (friction, conduction, induction) to prove the statement false and demonstrate understanding.

Question 2. The word 'electricity.' came from the word 'Elektron'.
Answer: True
In simple words: The term 'electricity' originates from the Greek word 'elektron', meaning amber, as the phenomena of static charge was first observed by rubbing amber.

🎯 Exam Tip: This question tests historical knowledge; confirming the linguistic origin of "electricity" is straightforward if you recall the connection to amber.

Question 3. When an inflated balloon is rubbed on silk, it develops a charge.
Answer: True
In simple words: Rubbing an inflated balloon with silk causes a transfer of electrons between the two materials due to friction, resulting in both becoming electrically charged.

🎯 Exam Tip: This is a classic example of triboelectric charging (charging by friction); understanding why this happens is key.

Question 4. An ebonite rod rubbed on woollen cloth develops a positive charge.
Answer: False. An ebonite rod rubbed on woollen cloth develops a negative charge
In simple words: When an ebonite rod is rubbed with a woollen cloth, electrons transfer from the wool to the ebonite, making the ebonite rod negatively charged and the woollen cloth positively charged.

🎯 Exam Tip: Remember the triboelectric series: ebonite typically gains electrons (becomes negative) when rubbed with wool, which loses electrons (becomes positive).

Question 5. A glass rod rubbed on woollen cloth develops a negative charge.
Answer: False. A glass rod rubbed on woollen cloth develops a positive charge
In simple words: When a glass rod is rubbed with a woollen cloth, the glass rod loses electrons to the wool, resulting in the glass rod becoming positively charged.

🎯 Exam Tip: Another example from the triboelectric series: glass tends to lose electrons and become positively charged when rubbed with wool.

Question 6. If the leaves of the electroscope spread only a little, the charge on them is less.
Answer: True
In simple words: The degree to which the leaves of an electroscope spread apart is directly proportional to the amount of electric charge present; a small spread indicates less charge.

🎯 Exam Tip: The divergence of electroscope leaves is a visual indicator of charge magnitude; greater spread means more charge, and less spread means less charge.

Question 7. An atom may have either a positive or a negative charge.
Answer: False. An atom does not have any charge
In simple words: A neutral atom contains an equal number of protons and electrons, resulting in a net zero charge; it is only when an atom gains or loses electrons that it becomes an ion with a net positive or negative charge.

🎯 Exam Tip: Distinguish between a neutral atom (zero net charge) and an ion (charged atom); a standard atom is inherently neutral.

Question 8. When two substances are rubbed on each other, like charges are developed on each.
Answer: False. When two substances are rubbed on each other unlike charges are developed on each
In simple words: When two substances are rubbed together, one typically gains electrons and becomes negatively charged, while the other loses electrons and becomes positively charged, meaning unlike charges are developed.

🎯 Exam Tip: Charging by friction always results in opposite charges on the two materials, preserving the overall charge conservation.

Question 9. High rise buildings have lightning conductors.
Answer: True
In simple words: High-rise buildings are commonly equipped with lightning conductors to protect them from direct lightning strikes by providing a safe path for the electrical current to the ground.

🎯 Exam Tip: Lightning conductors are a standard safety feature for tall structures; this reflects practical application of electrostatic principles.

Question 10. It is dangerous to stand under a tree in rainy and stormy weather.
Answer: True
In simple words: Standing under a tree during a thunderstorm is dangerous because trees are tall and can act as lightning rods, increasing the risk of a lightning strike hitting the tree and potentially harming anyone nearby.

🎯 Exam Tip: Emphasize that trees are conductors and provide a path for lightning, making them hazardous during storms, hence the importance of seeking lower shelter.

Exercise Give Scientific Reasons:

Question 1. Ordinarily, an atom does not have any charge.
Answer: 1. Every atom contains smaller particles with either positive or negative charge.
2. As the number of positively and negatively charged particles in an atom is equal, they neutralize each other.
3. As a result the atom has no charge.
In simple words: An atom is ordinarily neutral because it contains an equal number of positively charged protons in its nucleus and negatively charged electrons orbiting it, causing their charges to cancel out.

🎯 Exam Tip: The balance between protons and electrons is key to explaining atomic neutrality; mention both types of particles and their equal numbers.

Question 2. Charge cannot be developed on a copper rod.
Answer: Charge cannot be developed on a copper rod because only certain pairs of substances give rise to electric charge, on rubbing.
In simple words: A charge cannot be easily developed and retained on a copper rod by rubbing because copper is an excellent conductor, meaning any charges generated quickly move away or dissipate into the environment.

🎯 Exam Tip: Focus on copper's excellent conductivity; charges on conductors rapidly spread out or are grounded, preventing static buildup.

Question 3. High rise buildings have lightning conductors.
Answer: 1. High rise buildings are prone to lightning strikes during the monsoon.
2. When lightning strikes, a tremendous electric charge is transferred to the earth, which may damage the tall buildings.
3. To prevent this, high rise buildings have a forked metal rod, called a lightning conductor fitted on the top of the building.
4. The lower end of this rod is buried inside the earth.
5. If lightening strikes, the electric charge passes through this conductor and goes in to the earth. In this way the building is saved from damage.
In simple words: High-rise buildings use lightning conductors to protect against lightning strikes, which are more likely for tall structures during storms. The conductor provides a safe, low-resistance path for the immense electrical current to travel harmlessly into the earth, preventing structural damage and fires.

🎯 Exam Tip: Explain both the increased risk for tall buildings and the mechanism of the lightning conductor (providing a safe path to ground) to fully answer why they are used.

Question 4. It is dangerous to stand under a tree in rainy and stormy weather.
Answer: 1. Large amount of charges get built up in the clouds in rainy and storming weather.
2. Sometimes these charges are transferred to the earth in the form of a bolt of lightning.
3. Generally lightning strikes tall buildings and trees. If lightning strikes a tree then either the tree may fall or it may catch fire.
4. In both cases this would be dangerous for anyone standing under the tree, hence it is dangerous to stand under a tree in rainy and stormy weather.
In simple words: Standing under a tree during a thunderstorm is dangerous because trees are often the tallest objects in an open area, making them susceptible to lightning strikes. A direct hit can cause the tree to fall, explode, or conduct electricity to anyone sheltering underneath, leading to severe injury or death.

🎯 Exam Tip: Focus on the twin dangers: trees being struck due to height and their conductive nature, and the secondary risks of falling debris or electrocution.

Question 5. Repulsion is a test used for identifying an electrically charged object.
Answer: 1. When a charged object is brought near a neutral object, it gets attracted when two oppositely charged objects are brought close, they get attracted. Therefore, attraction is not a test.
2. But when two like charges are brought close only then repulsion takes place.
3. Therefore, repulsion is the sure test for identifying an electrically charged object.
In simple words: Repulsion is the definitive test for an electrically charged object because attraction can happen between a charged object and a neutral one due to induction. Only objects with like charges will repel each other, confirming both are charged.

🎯 Exam Tip: Clearly articulate why attraction is not a conclusive test (due to induction with neutral objects) but repulsion is, as it strictly requires two similarly charged objects.

Question 6. Mustard seeds when shaken vigorously in a glass bottle stick to the sides of the bottle.
Answer: When seeds are shaken they get electrically charged and therefore they stick to the neutral walls of the glass.
In simple words: When mustard seeds are shaken in a glass bottle, friction causes them to become electrically charged. These charged seeds then stick to the neutral glass walls due to the attractive force between a charged object and a neutral one.

🎯 Exam Tip: Explain the process of charging by friction (shaking generates charge) and the subsequent attraction between charged seeds and the neutral bottle walls.

Exercise Answer The Following:

Question 1. Why is the charge developed due to friction called static electric charge?
Answer: The charge developed due to friction is called static electric charge because the charge remains still on the object.
In simple words: The charge generated by friction is called static electric charge because it accumulates and stays in one place on the surface of the object rather than flowing away like current electricity.

🎯 Exam Tip: The key differentiator for "static" electricity is that the charges are "stationary" or "at rest" on the surface, not flowing.

Question 2. Why does the charge developed by induction disappear quickly?
Answer: The charge developed by induction disappears quickly because it is very weak.
In simple words: The charge developed by induction is temporary because it relies on the presence of an external charged object to maintain the charge separation. Once the external object is removed, the induced charges quickly redistribute, and the object returns to its neutral state.

🎯 Exam Tip: Explain that induced charges are temporary because they are not created by a permanent transfer of electrons but by a rearrangement due to an external field, which vanishes when the field is removed.

Question 3. Why do the leaves of a gold leaf electroscope fly apart when a charged body touches its disc?
Answer: The leaves of a gold leaf electroscope fly apart when a charged body touches its disc because like charges develop on both the leaves and hence they repel each other.
In simple words: When a charged body touches the disc of an electroscope, charge is transferred to the entire electroscope, including the gold leaves. Since both leaves acquire the same type of charge, they repel each other and spread apart.

🎯 Exam Tip: Focus on charge transfer (conduction) from the charged body to the electroscope, resulting in like charges on both leaves, which then repel.

Question Draw a neat labelled diagram of Gold leaf electroscope and describe it.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक गोल्ड लीफ इलेक्ट्रोस्कोप को दर्शाता है। इसमें एक धनावेशित छड़ को धातु की डिस्क के पास लाया गया है, जिससे धातु की छड़ और जुड़े हुए सोने के पत्ते भी आवेशित हो जाते हैं। बोतल के अंदर बंद सोने के पत्ते एक-दूसरे से दूर हटते हुए दिखाए गए हैं, जो उन पर समान आवेश के कारण प्रतिकर्षण को दर्शाता है। यह उपकरण किसी वस्तु पर विद्युत आवेश का पता लगाने के लिए उपयोग किया जाता है।
Answer: 1. This is a simple device to detect the electric charge on object.
2. It consists of a copper rod which has a metal disc at the upper end and two thin gold leaves at the other.
3. The rod is placed in a bottle so that the disc is above the bottle.
4. When an uncharged object is taken near the disc, the leaves remain closed.
5. When a charged object is taken near the disc, both the leaves are charged by the same electric charge, and repel each other.
6. When we touch the disc with our hand, the leaves collapse because the charge in the leaves goes into the earth through our body, and the leaves get discharged.
In simple words: A gold leaf electroscope consists of a metal rod with a disc at one end and two thin gold leaves at the other, enclosed in a bottle. It detects electric charge: when a charged object approaches, the leaves acquire like charges and repel, spreading apart; touching the disc discharges it as charge flows through your body to the earth.

🎯 Exam Tip: When describing the electroscope, ensure to explain its main parts (disc, rod, leaves, bottle) and how its operation (leaf divergence and collapse) indicates the presence and sometimes type of charge.

Exercise Use Your Brainpower:

Question 1. Do all the objects get charged by rubbing?
Answer: No. Only certain pairs of substances get charged on rubbing.
In simple words: Not all objects get charged by rubbing; charging by friction, or triboelectric charging, only occurs when certain pairs of materials with different affinities for electrons are rubbed together.

🎯 Exam Tip: Emphasize that the materials' properties (their position on the triboelectric series) determine whether they will transfer electrons and become charged by rubbing.

Question 2. Why does a charged balloon stick to a wall?
Answer: A charged balloon stick to a wall because there is always attraction between a charged object and an uncharged object.
In simple words: A charged balloon sticks to a wall because the balloon's static charge induces a temporary opposite charge on the surface of the neutral wall, creating an attractive electrostatic force between them.

🎯 Exam Tip: The key concept here is "induction" – the charged balloon rearranges charges in the neutral wall, leading to an attraction between the balloon and the wall's surface.

Question 3. Can we use leaves of some other metal instead of gold, in the electroscope? Which properties must that metal have?
Answer: We can use other metals than gold in gold leaf electroscope.
1. Only thing is that metal should be malleable and good conductor of electricity.
2. But the best is gold only because we can make extremely thin leaves of gold so even very small charge also can be detected.
In simple words: Yes, other malleable and highly conductive metals like aluminum could be used for electroscope leaves. However, gold is preferred because it can be beaten into extremely thin leaves, making the electroscope highly sensitive to even very small charges.

🎯 Exam Tip: For an alternative metal, highlight the need for both malleability (to make thin leaves) and good electrical conductivity for effective charge transfer and detection.

Question 4. What kind of damage is caused by a lightning strike?
Answer: Due to lightning strike, great damage can occur. It may cause forest fire and burn down things. Person on whom lightning strikes may die. It causes more temperature than sun.
In simple words: Lightning strikes can cause significant damage including starting forest fires, destroying property through direct impact or electrical surges, and being fatal to humans or animals due to the immense heat and current generated.

🎯 Exam Tip: List a range of potential damages (fire, property damage, fatalities, extreme heat) to demonstrate a comprehensive understanding of lightning's destructive power.

Question 5. What measures will you take to prevent the damage caused by lightning?
Answer: Following measures can be taken to prevent the damage caused by lightning: 1. Always put lightning conductor on tall buildings. 2. Do not stand on open ground, below a tree or near the electric or telephone pole during rain/ thunder storms. 3. Do not lean on wired fences. 4. Do not use plugged in electrical appliances. 5. Do not swim during thunder storms. 6. Stay in a pucca house with lightning conductor fitted on it.
In simple words: To stay safe from lightning, install lightning conductors on tall buildings, avoid open areas, trees, and electrical poles during storms, and remain indoors in a solid structure, avoiding plugged appliances.

🎯 Exam Tip: Listing specific preventive actions for lightning strikes shows a clear understanding of safety protocols.

Question 6. Why is the upper end of the lighting conductor pointed?
Answer: 1. The pointed end makes it possible to increase the electric field near the point. The electric field set up at pointed end is high. 2. If the discharge of cloud occurs it would be easily passed through the lightening conductor to the ground and damage to the building is averted.
In simple words: The pointed end of a lightning conductor creates a concentrated electric field, allowing it to easily attract and safely channel a lightning discharge into the ground, protecting the building.

🎯 Exam Tip: Emphasize the principle of electric field concentration at sharp points to demonstrate a scientific understanding.

Question 7. Why is coal and salt added to the pit in the ground?
Answer: Coal and salt is filled in the pit and also there is a provision for pouring water into it. This helps to spread electric charge quickly into ground and prevent damage.
In simple words: Coal and salt are added to the pit with water to increase the conductivity of the soil, ensuring that electric charges from a lightning strike can quickly and safely dissipate into the ground, preventing damage.

🎯 Exam Tip: Focus on the role of coal and salt in improving electrical conductivity for effective earthing.

Observe The Given Diagram And Answer The Questions Given.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र गोल्ड लीफ इलेक्ट्रोस्कोप की कार्यप्रणाली को दर्शाता है। इसमें एक धातु की डिस्क से जुड़ी एक तांबे की छड़ होती है, जिसके निचले सिरे पर दो पतली सोने की पत्तियां लगी होती हैं, जो एक बोतल के अंदर बंद होती हैं। यह उपकरण वस्तु पर विद्युत आवेश का पता लगाने और उसकी प्रकृति को समझने के लिए उपयोग किया जाता है।

Question a. Name the phenomenon happening in the diagram and define it
Answer: Phenomenon happening is static electricity. When certain objects are rubbed against each other, they produce an electric charge on their surface at the place of friction. This is due to electrons which remain for a short time. This is called static electricity.
In simple words: The phenomenon shown is static electricity, which occurs when objects rub together, causing electrons to transfer and a temporary electric charge to build up on their surfaces.

🎯 Exam Tip: Clearly defining static electricity and its cause (friction leading to electron transfer) is crucial for a complete answer.

Question b. What do you observe in “b” and "c" part of the diagram?
Answer: In 'b', we observe attraction between the charged balloon and the uncharged aluminium ball. In 'c', we observe that the charge has been transferred to the aluminium ball and due to the same (like) charge, repulsion is observed.
In simple words: In part 'b', the charged balloon attracts the uncharged aluminum ball, while in part 'c', after charge transfer, the aluminum ball becomes charged like the balloon, leading to repulsion.

🎯 Exam Tip: Distinguish between attraction (charged and uncharged) and repulsion (like charges) as key indicators of electrostatic interactions.