Static Electricity | Class 7 | Science | Chapter 8 | Maharashtra State Board
Welcome to our enlightening YouTube video, where we explore the captivating world of electricity, from Benjamin Franklin’s ground breaking experiments to the modern safety measures protecting us from lightning strikes. In this educational adventure, we delve into the concepts of electric charge, static electricity, frictional electricity, and lightning strikes, all while exploring the vital role they play in our daily lives. Discover the secrets behind atmospheric electric charge and the ingenious lightning conductor, gaining insights into how these phenomena affect us and our environment. Uncover the electrifying history and science behind these keywords, as we embark on a quest to demystify the wonders of electricity and lightning. From the early curiosity of Benjamin Franklin to the modern solutions that protect us from lightning strikes, this video is your key to understanding the powerful forces at play. Don’t forget to like, share, and subscribe to our channel for more enlightening content. Stay charged with knowledge as we journey through the realms of science and discovery!
Questions & Answers
1. Choose the correct option and fill in the blanks.
(always repulsion, always attraction, displacement of negative charge, displacement of positive charge, atom, molecule, steel, copper, plastic, inflated balloon, charged object, gold)
1. There is always repulsion between like charges.
2. Displacement of negative charge is responsible for generation of electric charge in an object.
3. A lightning conductor is made of a copper strip.
4. Steel does not get electrically charged easily by rubbing.
5. There is always attraction when opposite electric charges come near each other.
6. A charged object can be detected with an electroscope.
2. Explain why it is not safe to go out with an umbrella when there is heavy rain, lightning or thunder.
Ans. Using an umbrella during heavy rain, lightning, or thunder is not safe because:
Lightning Risk: Umbrellas can attract lightning due to their metal parts, putting you at risk of getting struck by lightning.
Electric Shock: If lightning hits your umbrella, it can conduct electricity and harm you.
Wind Danger: Strong winds during storms can turn your umbrella into a hazard, making it hard to control.
Visibility Issues: Umbrellas can block your view, making it difficult to see dangers like flooding or fallen objects.
Safer Alternatives: It’s better to seek shelter indoors during these conditions or use a raincoat instead of an umbrella.
3. Answer in your own words.
1. How will you protect yourself from lightning?
Ans. To protect yourself from lightning:
1. Seek Shelter: Go indoors or find a sturdy, enclosed building.
2. Avoid Water: Stay away from water sources, including swimming pools and showers.
3. Stay Away from Trees: Trees can attract lightning; stay clear of them.
4. Don’t Use Electrical Appliances: Avoid using electrical devices or landline phones.
5. Stay Low: If indoors isn’t an option, crouch down to reduce the risk of a lightning strike.
6. Wait It Out: Wait at least 30 minutes after the last thunder before going back outside.
2. How are charges generated?
Ans. Charges are generated when electrons (negatively charged particles) move from one object to another, creating an imbalance of positive and negative charges. This movement of electrons can happen through friction (rubbing objects together), contact (touching two objects), or induction (bringing a charged object near another, which causes the charges to redistribute).
3. In the lightning conductor, what provision is made for spreading the electricity into the ground? Ans.
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 and prevent damage.
4. Why do farmers stick an iron staff into the ground while working in the field in rainy conditions? Ans.
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.
5. Why is lightning not seen every day during the rainy season? Ans.
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.
4. What are the characteristics of a static electric charge?
1. What are the characteristics of a static electric charge? Ans. Characteristics of a static electric charge:
Stationary: It remains in one place on an object’s surface.
Immobile: It does not flow as an electric current.
Attraction/Repulsion: Charged objects can attract or repel each other.
Discharge: It can be discharged when in contact with a conductor.
Can Be Generated: It can be generated by friction, induction, or contact.
5. What is the damage caused by lightning? How will you create awareness to prevent it?
1. What is the damage caused by lightning? How will you create awareness to prevent it? Ans. Damage caused by lightning:
Fires: Lightning strikes can ignite fires in buildings, forests, and other structures.
Electrical Damage: Lightning can damage electrical and electronic equipment.
Injury and Death: Lightning can cause injuries or fatalities to humans and animals.
Structural Damage: Buildings and trees can be damaged or destroyed by lightning strikes.
Power Outages: Lightning can disrupt power supplies.
Creating awareness to prevent lightning damage:
Educate: Conduct awareness campaigns on lightning safety through schools and community organizations.
Lightning Rods: Encourage the installation of lightning rods on buildings.
Safety Tips: Share safety tips like seeking shelter during storms and avoiding open fields.
Apps and Alerts: Use weather apps and alerts to monitor lightning activity.
Emergency Plans: Develop and promote emergency plans for lightning storms.
Lightning Safety Week: Observe Lightning Safety Week to raise awareness annually.
Stand on only wood, a plastic sheet or sack of jute.
E X T R A
1. Choose the correct option and fill in the blanks.
(always repulsion, always attraction, displacement of negative charge, displacement of positive charge, atom, molecule, steel, copper, plastic, inflated balloon, charged object, gold)
1. Named the electric charges as positive charge and negative charge. Ans. Benjamin Franklin
2. Each atom contains a stationary charge and moving charges. Ans. positive, negative
3. Each atom is electrically Ans. neutral
4. Amber is called in the Greek language. Ans. electron
5. The charges of electricity are absorbed in moist air. Ans. static
6. Electrically charged objects uncharged objects. Ans. attract
7. is used as a test for identifying an electrically charged object. Ans. Repulsion
8. The property of amber to attract things was named electricity by in 1646 AD. Ans. Thomas Brown
9. The electric charge generated by stays only as long as the charged object is near to it. Ans. induction
10. A simple device is used to detect the electric charge on an object. Ans. gold leaf electroscope
11. Lightning is a form of Ans. electric charge
12. The gas protects us from the harmful ultra violet rays coming from the sun. Ans. ozone
13. The is a device used for protection from a lightning strike. Ans. lightning conductor
14. Due to the energy of the lightning, the oxygen in the air is converted into Ans. ozone
2. Say whether true or false, correct and rewrite the false statement:
1. Charges cannot be transferred from one body to another. Ans. False. Charges can be transferred from one body to another
2. The word ‘electricity.’ came from the word ‘Elektron’. Ans. True
3. When an inflated balloon is rubbed on silk, it develops a charge. Ans. True
4. An ebonite rod rubbed on woollen cloth develops a positive charge. Ans. False. An ebonite rod rubbed on woollen cloth develops a negative charge
5. Glass rod rubbed on woollen cloth develops a negative charge. Ans. False. A glass rod rubbed on woollen cloth develops a positive charge
6. If the leaves of the electroscope spread only a little, the charge on them is less. Ans. True
7. An atom may have either a positive or a negative charge. Ans. False. An atom does not have any charge
8. When two substances are rubbed on each other, like charges are developed on each. Ans. False. When two substances are rubbed on each other unlike charges are developed on each
9. High rise buildings have lightning conductors. Ans. True
10. It is dangerous to stand under a tree in rainy and stormy weather. Ans. True
3. Give scientific reasons:
1. Ordinarily, an atom does not have any charge.
Ans. Ordinarily, an atom does not have any charge because it has an equal number of positively charged protons and negatively charged electrons. These charges balance each other out, resulting in a neutral atom.
2. Charge cannot be developed on a copper rod. Ans. Charge cannot be developed on a copper rod because copper is a good conductor of electricity. When it is rubbed, any charge it acquires is quickly neutralized and distributed throughout the rod due to its high conductivity, leaving it electrically neutral.
3. High rise buildings have lightning conductors.
Ans. High-rise buildings have lightning conductors to protect them from lightning strikes. Lightning conductors provide a safe path for lightning to follow, directing it away from the building and into the ground, thereby preventing damage, fires, or electrical surges that can occur from a lightning strike.
4. It is dangerous to stand under a tree in rainy and stormy weather.
Ans. It is dangerous to stand under a tree in rainy and stormy weather because trees can attract lightning strikes during a thunderstorm. Lightning can hit the tall tree and travel down its trunk, potentially injuring or even killing anyone standing nearby. It is safer to seek shelter in a sturdy, enclosed structure during such weather conditions.
5. Repulsion is a test used for identifying an electrically charged object.
Ans. Repulsion is a test used for identifying an electrically charged object because like charges (positive and positive or negative and negative) will repel each other. If two objects with the same charge are brought close, they will push each other away due to the electrostatic force of repulsion. This behaviour helps confirm the presence of an electric charge on the objects.
6. Mustard seeds when shaken vigorously in a glass bottle stick to the sides of the bottle. Ans. Mustard seeds stick to the sides of the glass bottle when shaken vigorously because of the phenomenon known as static electricity. When the seeds rub against the glass as they move, they can acquire an electric charge. This charged state causes them to be attracted to and stick to the oppositely charged surface, which in this case is the glass.
4. Answer the following:
1. Why is the charge developed due to friction called static electric charge? Ans. The charge developed due to friction is called 1 static electric charge because the charge remains still on the object.
2. Why does the charge developed by induction disappear quickly? Ans. The charge developed by induction disappears quickly because it is very weak.
3. Why do the leaves of a gold leaf electroscope fly apart when a charged body touches its disc?
Ans. 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.
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