Chapter 12: Some Natural Phenomena

1. What is lightning?

A giant electric spark in the atmosphere.(Vatavaran mein ek vishal vidyut chingari).

2. How can objects be charged?

By rubbing them together.(Unhein aapas mein ragad kar).

3. How many types of charges are there? Name them.

Two types: Positive and Negative.(Do prakaar: Positive aur Negative).

4. What happens when like charges are brought near each other?

They repel each other.(Ve ek dusre ko pratikarshit karte hain).

5. What happens when unlike charges are brought near each other?

They attract each other.(Ve ek dusre ko aakarshit karte hain).

6. Name the device used to detect charge on an object.

Electroscope.(Vidyutdarshi).

7. What is earthing?

Transferring charge from a charged object to the Earth.(Charged vastu se charge Prithvi mein transfer karna).

8. Where do charges accumulate in thunderclouds?

Positive usually at top, Negative usually at bottom.(Positive aamtaur par upar, Negative neeche).

9. What is an electric discharge?

The meeting of positive and negative charges, often producing light and sound.(Positive aur negative charge ka milna, jisse aksar roshni aur awaaz nikalti hai).

10. Name a device used to protect buildings from lightning.

Lightning Conductor.(Tadit Chalak).

11. What is an earthquake?

Sudden shaking or trembling of the Earth.(Prithvi ka achaanak hilna ya kaampna).

12. What is the main cause of earthquakes?

Movement of Earth’s tectonic plates.(Prithvi ki tectonic plates ka hilna).

13. What are fault zones?

Weak zones at the boundaries of Earth plates where earthquakes are more likely.(Plate ki seemaon par kamzor zone jahan bhukamp zyada aate hain).

14. Name the instrument used to record earthquakes.

Seismograph.(Seismograph).

15. Name the scale used to measure earthquake magnitude.

Richter Scale.(Richter Scale).

16. What magnitude on Richter scale indicates a major earthquake?

Higher than 7.

1. Explain charging by rubbing with an example.

• When two suitable objects are rubbed, electrons transfer from one to the other.(Jab do cheezon ko ragadte hain, electron ek se dusre par jaate hain).
• The object losing electrons becomes positively charged (+).(Electron khone wali cheez positive (+) ho jaati hai).
• The object gaining electrons becomes negatively charged (-).(Electron paane wali cheez negative (-) ho jaati hai).
• Example: Rubbing glass rod with silk makes glass rod positive and silk negative.(Udaharan: Kanch ki rod ko silk se ragadne par rod positive, silk negative).

2. Describe how an electroscope works.

• An electroscope detects charge.(Electroscope charge ka pata lagata hai).
• It has a metal rod with two light metal leaves (like foil) at the bottom, often enclosed in a jar.
• When a charged object touches the top metal part, charge transfers through the rod to the leaves.(Jab charged vastu upar touch karti hai, charge pattiyon tak jaata hai).
• Both leaves get the same type of charge (either both + or both -).(Dono pattiyon par ek jaisa charge aata hai).
• Since like charges repel, the leaves move apart (diverge). ↔️(Samaan charge repel karte hain, isliye pattiyan fail jaati hain). If object is uncharged, leaves don’t move.

3. Explain the process of electric discharge during lightning.

• During thunderstorms, charges separate in clouds (+ve at top, -ve at bottom usually). Ground also gets induced +ve charge. (Toofan mein, baadalon mein charge alag ho jaate hain).
• When charge build-up becomes very large, the insulating air breaks down.(Jab charge bahut zyada ho jaata hai, toh hawa use rok nahi paati).
• A huge electric current flows rapidly between clouds, or between cloud and ground, to neutralize the charges.(Charge ko neutral karne ke liye bahut tez current behta hai).
• This rapid flow of charge through air is the electric discharge, seen as lightning ⚡ and heard as thunder 📣.

4. What is a lightning conductor? How does it protect buildings?

• A lightning conductor is a safety device installed on tall buildings.(Tadit chalak unchi imaraton par laga safety device hai).
• It consists of a metal rod (usually copper) extending from above the building down to a metal plate buried deep in the ground 🌍.
• If lightning strikes the building, it hits the pointed metal rod first.
• The conductor provides an easy, low-resistance path for the lightning charge to flow directly into the Earth, bypassing the building structure. (Yeh bijli ke charge ko zameen mein jaane ka aasan raasta deta hai).
• This prevents the huge current from passing through the building and causing damage or fire.🛡️

5. List three safety measures to take during lightning if you are outdoors.

• Find a safe shelter like a house or car immediately.
• If no shelter, stay away from tall trees, poles, metal objects. 🌳❌
• Do not lie flat on ground; squat low with head between hands 🙇.
• Stay away from water bodies 💧❌.
• (Choose any three)

6. List three safety measures to take during lightning if you are indoors.

• Avoid contact with telephone cords, electrical wires, metal pipes.
• Do not use corded phones (mobiles are safer 📱).
• Unplug electrical appliances (TVs, computers) 🔌❌.
• Avoid bathing or contact with running water 🚿❌.
• (Choose any three)

7. What is the main cause of earthquakes?

• Caused by sudden disturbances deep inside the Earth’s crust 🌍.
• The crust is made of moving plates.
• Main cause is the movement of these tectonic plates: collision, brushing past, or one going under another. ↔️💥 (Mukhya karan hai tectonic plates ka hilna/takrana).
• This movement releases huge amount of energy as seismic waves, causing shaking on the surface.

8. What are seismic or fault zones?

• The Earth’s crust is fragmented into plates.
• The boundaries where these plates meet are generally weaker zones. (Jahan plates milti hain, woh seemayein kamzor zone hoti hain).
• Movements causing earthquakes are more likely to occur along these boundaries.
• These weak boundary zones are called seismic zones or fault zones ⚡🌍❗.(In kamzor seema zones ko seismic ya fault zones kehte hain).

9. What is a seismograph and what is the Richter scale?

• Seismograph 📉: An instrument that detects and records the seismic waves produced during an earthquake.(Bhukamp ke dauran paida hui seismic waves ko record karne wala upkaran).
• Richter Scale: A scale used to measure the magnitude (power/energy released) of an earthquake. It’s a logarithmic scale; each whole number increase represents a large jump in magnitude. (Bhukamp ki shakti (magnitude) maapne ka scale. Logarithmic hai, har number pichle se bahut zyada shaktishali hota hai).

10. Mention three precautions to take inside the house during an earthquake.

• Drop, Cover, Hold On! (Jhuko, Chhipo, Pakdo!).
• Take shelter under a sturdy table or desk; hold on until shaking stops.🔽🛡️ (Mazboot table ke neeche chhip jao).
• Stay away from heavy objects, windows, mirrors that might fall/break.
• If in bed, stay there and protect head with a pillow.🛌🛡️

11. Why is construction in seismic zones different?

• Buildings in seismic (fault) zones are at higher risk of earthquake damage. (Seismic zone ki imaraton ko bhukamp se zyada khatra hai).
• They should be designed by qualified professionals to be ‘quake-safe’.
• Construction using lighter materials like timber or mud might be preferred over heavy construction in high-risk areas. (Halke material jaise lakdi/mitti ka istemal behtar ho sakta hai).
• Reinforcement and specific structural designs are used to help buildings withstand shaking.(Mazbooti aur khaas design jhatke sehne mein madad karte hain).

1. Explain the process of charging by rubbing and the interaction between different types of charges.

Charging by Rubbing:

• Normally objects are electrically neutral (equal +ve & -ve charge).
• When certain objects are rubbed together, friction causes transfer of electrons (tiny negative particles) from one object to another. (Ragadne se electron ek vastu se dusri par jaate hain).
• Object losing electrons becomes positively charged (➕). Ex: Glass rod rubbed with silk.
• Object gaining electrons becomes negatively charged (➖). Ex: Silk rubbed with glass rod.
• Both objects become charged.

Interaction of Charges:

• There are two types: Positive (+) and Negative (-).
• Like Charges Repel: Positive repels positive; negative repels negative. ↔️❌ (Samaan charge ek dusre ko dhakelte hain).
• Unlike Charges Attract: Positive attracts negative. ➡️💖⬅️ (Vipreet charge ek dusre ko kheench te hain).
• This attraction/repulsion is the electric force. A charged object can also attract an uncharged (neutral) object.

2. Explain how lightning occurs during a thunderstorm.

Lightning is a large-scale electric discharge.

• Charge Separation: During thunderstorm development, air currents 🌬️ and movement of water droplets 💧/ice crystals cause charges to separate within clouds ☁️. Positive charges (➕) tend to collect near the upper parts, and negative charges (➖) near the lower parts. The ground below also often acquires an induced positive charge (➕).(Toofan mein baadalon mein charge alag ho jaate hain (+ upar, – neeche)).
• Charge Buildup: These positive and negative charges accumulate and increase in magnitude. (Charge ikattha hokar badhta jaata hai).
• Air Breakdown: When the potential difference (due to charge separation) becomes very large, the insulating property of air breaks down. (Jab charge bahut zyada ho jaata hai, toh hawa current ko rok nahi paati).
• Electric Discharge: Negative charges from the cloud rush towards the positive charges (either on the ground or in another part of the cloud) creating a path through the air. This massive flow of electric charge is called electric discharge.(Negative charge positive charge ki taraf tezi se behta hai. Is charge ke bahav ko electric discharge kehte hain).
• Lightning & Thunder: This discharge heats the air rapidly, producing the bright flash of light we see as lightning ⚡. The rapid heating also causes air to expand suddenly, creating sound waves we hear as thunder 📣.(Yeh discharge hawa ko garam karke roshni (bijli) aur awaaz (garaj) paida karta hai).

3. Discuss the safety measures one should take during lightning, both outdoors and indoors.

Safety During Lightning:

• Outdoors 🌲:
  • Seek immediate shelter in a building 🏠 or hard-top vehicle 🚗.
  • If no shelter, find a low-lying area away from tall trees 🌳❌, poles, metal structures.
  • Squat low 🙇, minimize contact with ground, don’t lie flat.
  • Stay away from water 💧❌.
• Indoors 🏠:
  • Avoid contact with electrical wiring, metal pipes, telephone cords ☎️❌.
  • Avoid using corded phones (use mobiles/cordless 📱).
  • Unplug electrical appliances 🔌❌ (TV, computer).
  • Avoid bathing/contact with running water 🚿❌ as plumbing can conduct electricity.
  • Stay away from windows/doors.

Lightning can be dangerous, following safety measures is crucial.

4. What are earthquakes? Explain their main cause and how they are measured.

Earthquake: A sudden shaking or trembling of the Earth’s surface 🌍〰️.

Main Cause (Mukhya Karan):

• Earth’s crust is made of large moving **Tectonic Plates**.
• Earthquakes are mainly caused by the sudden movement, collision, or rubbing of these plates along their boundaries (fault zones). ↔️💥 (Mukhya karan tectonic plates ka hilna/takrana hai).
• This releases stored energy as **Seismic Waves** that travel through the Earth and cause shaking.

Measurement (Maapan):

• Shaking (seismic waves) is recorded by an instrument called a **Seismograph** 📉.
• The magnitude (power/energy) of the earthquake is measured on the **Richter Scale**. This scale is logarithmic (each number increase is a huge jump in energy). Destructive quakes are usually > 7.

5. Since earthquakes cannot be predicted, what precautions should be taken for protection against them?

Preparedness is key as earthquakes are unpredictable:

Building Safety (Especially in Seismic Zones):

• Consult qualified architects/structural engineers for quake-safe building designs.
• Use lighter construction materials (timber, mud) over heavy ones where appropriate.
• Ensure roofs are light.
• Fix cupboards, shelves, water heaters securely to walls.

General Precautions:

• Be aware of safe spots (under tables, against inside corners/walls, away from windows/mirrors/heavy objects).
• Keep fire extinguishers handy (fires can break out). 👨‍🚒
• Have an emergency kit with essentials.
• Know how to turn off main switches for gas, water, electricity if needed.

During an Earthquake:

• If indoors: Drop, Cover, Hold On! 🔽🛡️
• If outdoors: Move to clear area away from buildings/trees/power lines. Drop to ground. 🏞️
• If in vehicle: Stop in clear area, stay inside. 🚗🛑

6. Describe how charge is transferred using an electroscope.

An electroscope helps demonstrate charge transfer:

• It typically has a metal knob/disc at the top connected by a metal rod to two lightweight metal leaves (e.g., aluminum foil) at the bottom, enclosed in a protective jar.
• Step 1: Touching with Charged Object: Bring a charged object (e.g., a rubbed plastic ruler – negatively charged) and touch it to the top metal knob.
• Step 2: Conduction: Since the metal rod and leaves are conductors, the charge (electrons in case of the ruler) travels from the charged object, down the rod, and spreads onto both metal leaves. (Charge rod se hota hua dono pattiyon par fail jaata hai).
• Step 3: Repulsion: Both leaves now acquire the same type of charge (negative in this case). Since like charges repel, the leaves push each other apart and diverge (move away from each other). ↔️❌ (Dono pattiyon par same charge (-) aata hai, isliye woh ek dusre ko repel karke fail jaati hain).
• Step 4: Detecting Uncharged Object: If an uncharged object touches the knob, no charge transfer occurs, and the leaves do not diverge or collapse if already charged.
• Step 5: Earthing: If you touch the knob of a charged electroscope with your hand, the charge from the leaves travels through the rod, your body (a conductor), into the Earth 🌍. The leaves lose their charge and collapse back together. This demonstrates earthing.

The amount of divergence roughly indicates the amount of charge.

7. Explain the types of charges and their interaction with examples.

There are two fundamental types of electric charge:

• 1. Positive Charge (➕): An object becomes positively charged when it *loses* electrons during rubbing. Example: A glass rod rubbed with silk. (Jab vastu electron *kho* deti hai. Udaharan: Silk se ragdi hui kanch ki rod).
• 2. Negative Charge (➖): An object becomes negatively charged when it *gains* electrons during rubbing. Example: A plastic straw rubbed with polythene or dry hair. (Jab vastu electron *prapt* kar leti hai. Udaharan: Polythene/baalon se ragda hua plastic straw).

Interaction between Charges:

• Like Charges Repel: Objects having the same type of charge push each other away.
  • A positively charged object repels another positively charged object.
  • A negatively charged object repels another negatively charged object.
  • Example: Bring two balloons rubbed with wool near each other; they will move apart. 🎈↔️🎈
• Unlike Charges Attract: Objects having opposite types of charge pull towards each other.
  • A positively charged object attracts a negatively charged object. ➕💖➖
  • Example: A balloon rubbed with wool (becomes negative) will attract small pieces of paper (which get induced charge, or might be slightly positive). 🎈➡️📄

This interaction (attraction/repulsion) is due to the electric force between charges.

8. Can lightning strike even without clouds? Why or why not?

No, typically lightning as we know it (the large electric discharge seen during thunderstorms) requires clouds.

• Mechanism Requires Clouds: The primary mechanism for lightning involves charge separation *within* clouds or between clouds and the ground. This separation happens due to the movement and collisions of ice crystals, water droplets, and hail within the thundercloud ⛈️. (Bijli ke liye baadalon ke andar charge alag hona zaroori hai, jo hawa aur paani/barf ke kano ki halchal se hota hai).
• Charge Accumulation: Clouds act as large bodies where significant amounts of positive (➕) and negative (➖) charge can accumulate separately. (Baadal aise bade structures hain jahan bahut saara charge alag-alag jama ho sakta hai).
• Potential Difference: This massive charge separation creates a very large electrical potential difference between different parts of the cloud or between the cloud and the ground.
• Discharge Path: When this potential difference is large enough, it overcomes the insulating capacity of the air, creating a path for the electric discharge (lightning ⚡).

Without the clouds providing the mechanism for large-scale charge separation and accumulation, the conditions necessary for a typical lightning strike between cloud-to-ground or cloud-to-cloud are not met.

(Note: Other forms of electric discharge can occur in specific conditions like volcanic eruptions, but thunderstorm lightning needs clouds).

9. Discuss why Earth’s tectonic plates move and how this relates to earthquakes.

The movement of Earth’s tectonic plates is the primary driver of earthquakes.

• Earth’s Structure: The Earth has layers. The outermost rigid layer is the **lithosphere**, which includes the crust and the upper part of the mantle. The lithosphere is broken into several large and small pieces called **tectonic plates**. (Prithvi ki bahari parat (lithosphere) kai tukdon (tectonic plates) mein tooti hui hai).
• Floating Plates: These plates essentially ‘float’ on a hotter, semi-molten layer beneath them called the **asthenosphere**. (Yeh plates neeche ki garam, pighli hui parat (asthenosphere) par ‘tairti’ hain).
• Convection Currents: Heat from the Earth’s core creates slow-moving convection currents within the mantle (and asthenosphere). Hotter material rises, cooler material sinks. ♨️🔄 (Prithvi ke core ki garmi se mantle mein dheeme convection currents chalte hain).
• Plate Movement: These convection currents drag the overlying tectonic plates along with them, causing the plates to move slowly but constantly (a few centimeters per year). (Yeh currents upar ki plates ko apne saath kheench te hain, jisse plates hilti rehti hain).
• Earthquakes at Boundaries: Most geological activity, including earthquakes, happens at the boundaries where plates interact:
  • Colliding 💥: Plates push against each other (causes mountain building).
  • Moving Apart: Plates pull away from each other (causes rifts/new crust).
  • Sliding Past ↔️: Plates slide horizontally past each other.
• When plates move, tremendous stress builds up in the rocks at the boundaries. When this stress exceeds the rock’s strength, the rock suddenly breaks or slips along a **fault**, releasing the stored energy as **seismic waves**, which we feel as an earthquake 〰️. (Jab plates hilti hain, toh boundaries par stress banta hai. Jab stress zyada ho jaata hai, toh chattaan achaanak toot ti ya phisalti hai, jisse seismic waves (bhukamp) nikalti hain).

10. How can earthquake-safe buildings be constructed in high-risk zones?

Constructing earthquake-safe buildings in seismic zones involves specific design and material considerations:

• Consult Experts: Always consult qualified architects and structural engineers who understand seismic design principles. (Yogya architect/engineer se salah lein).
• Foundation: The building’s foundation needs to be strong and potentially isolated from ground vibrations using base isolation techniques (though complex). (Neenv mazboot honi chahiye).
• Lightweight Materials: Using lighter construction materials like timber (wood) or mud is often safer than heavy materials like bricks or concrete in high-risk areas, as lighter structures experience less force during shaking. (Halke material (lakdi, mitti) bhaari material se zyada surakshit ho sakte hain).
• Roof Structure: Roofs should be as light as possible. Heavy roofs can collapse easily. Thatched or tin roofs might be preferred over heavy concrete slabs in some designs. (Chhat jitni ho sake halki honi chahiye).
• Structural Reinforcement: Incorporating features like reinforced concrete cement (RCC), steel frames, shear walls, and proper joining of walls/columns helps the structure resist shaking forces and remain intact. (RCC, steel frame jaisi cheezon se structure ko mazbooti dena).
• Flexible Structure: Designing the building frame to have some flexibility can help it sway during an earthquake without collapsing.
• Secure Fixtures: Heavy items like cupboards, water heaters, shelves must be firmly fixed to walls to prevent them from falling during tremors.

While no building can be 100% earthquake-proof, these measures significantly improve safety and reduce the risk of collapse.