In-text — Storms, Thunderstorms and Lightning — Pressure, Winds, Storms, and Cyclones

1. 14 marksCuriosity Grade 8, Chapter 6, page 90, section 6.5

   Explain how a storm forms. What is a storm?

   Hint. Follow the chapter's chain from heated land to falling rain.

   The chain, as the chapter gives it:

   1. When land gets heated, the warm and moist air, being lighter, rises, thereby creating a low pressure area.
   2. Cooler air from the surrounding high-pressure areas flows to take its place.
   3. This air, in turn, gets heated and rises. This results in a continuous process of wind circulation.
   4. As the rising air expands, it cools and moisture in it condenses to form water droplets, creating clouds.
   5. The water droplets merge to form heavier drops, which come down as rain, hail, or snow.

   Definition. The strong winds accompanied by rain is called a storm.

   ✦ Two ingredients are doing all the work, and the Snapshot names them: Important requirements for the formation of thunderstorms are moisture and strong winds. Heat alone gives you rising air and wind; it is the moisture in that air that gives you clouds and rain when it condenses.

   Which is why the chapter adds: In hot, humid, and tropical regions like India, storms are more frequent. Hot supplies the heating, humid supplies the moisture.

   Step 3 is the one students skip. The process does not happen once — the replacement air is heated in its turn and rises too, so a continuous circulation is set up. That is what keeps a storm going instead of it being a single puff of rising air.

2. 24 marksCuriosity Grade 8, Chapter 6, pages 90-91

   How do electric charges come to be present in a storm cloud?

   Hint. The chapter points back to an activity from Chapter 5.

   By rubbing — the same process as rubbing a balloon on a woollen cloth.

   The steps:

   1. Under certain conditions, warm air rises to great heights that the low temperature there converts water droplets into ice particles. So the cloud now holds both water droplets and ice particles.
   2. Strong winds blowing upwards and downwards (Fig. 6.15) facilitate rubbing between water droplets and ice particles.
   3. You have learnt in the chapter 'Exploring Forces' that when two objects are rubbed against each other, they get charged.
   4. In this case, strong winds blowing upwards and downwards and rubbing against each other cause static electric charges to develop within the clouds.

   ✦ This is a genuinely satisfying link back to Chapter 5. There you rubbed a plastic scale with polythene and picked up bits of paper, and rubbed two balloons with wool and watched them repel. The physics of a thundercloud is the same physics, on a scale of kilometres, with ice and water doing the rubbing instead of your hands.

   Both ingredients of the Snapshot are needed here too: the moisture supplies the droplets and the ice, and the strong winds supply the rubbing. Neither alone would charge a cloud.

   The next step — how those charges arrange themselves — is what makes lightning possible.

3. 34 marksCuriosity Grade 8, Chapter 6, page 91

   Describe how charge is separated within a thundercloud, and how the ground becomes charged.

   Hint. Which particles go up, and which stay low?

   Within the cloud.

   Particles	Charge	Where they go
   Ice particles — lighter	Positive	move upwards and occupy the upper part of the clouds
   Water droplets — heavier	Negative	occupy the lower part of the clouds

   Thus, a charge separation within the cloud takes place.

   And on the ground. When the negatively charged lower part of the cloud moves closer to the ground, it causes the ground and nearby objects, such as trees or buildings, to become positively charged (Fig. 6.16).

   ✦ Note the two different mechanisms at work here, and do not merge them. Inside the cloud, the separation happens because the charged particles are of different weights and the up-and-down winds sort them by height. On the ground, nothing is being sorted at all — the ground becomes positively charged simply because a large negative charge has come close to it. It is Chapter 5's electrostatic force acting at a distance.

   Why this arrangement matters. You now have a large negative region low in the cloud and a large positive region on the ground beneath it, separated only by air. That is the arrangement lightning needs — and the only thing preventing it is that air does not normally conduct.

   The Snapshot's version: Strong winds moving upwards and downwards facilitate rubbing of ice particles with water droplets, causing electric charges to develop in clouds.

4. 45 marksCuriosity Grade 8, Chapter 6, page 91

   Explain the process that causes lightning. Where can lightning occur?

   Hint. Air normally prevents this. Explain what changes.

   The process.

   1. Charge separation leaves a large negative charge in the lower part of the cloud and a large positive charge on the ground and on nearby objects such as trees and buildings.
   2. Normally, air acts as an electrical insulator and does not let opposite charges meet. So nothing happens at first, and the charges keep building up.
   3. But when the build up of charges becomes very large, the insulating property of air breaks down.
   4. A sudden flow of charges takes place, producing a bright flash of light called lightning.

   Where it can occur. Lightning can occur as opposite charges collide within a cloud, between clouds, or between clouds and the ground. All three are lightning — the cloud-to-ground kind is simply the one we notice most.

   And the sound. Lightning rapidly heats up the air around it, causing the air to expand and produce a loud sound known as thunder. So thunder is not a separate event; it is the noise made by the air the flash has just heated.

   ✦ Step 2 is the one the exercises test. It is easy to describe lightning as charges meeting, and to forget why they could not meet earlier. Air is an insulator, so the charges accumulate rather than trickling away — and it is precisely that accumulation, released all at once when the air finally gives way, that makes the flash so violent. Exercise question 6 turns this exact point into a question.

   Definition to have ready: A storm accompanied by lightning and thunder is called a thunderstorm.

5. 54 marksCuriosity Grade 8, Chapter 6, pages 90-91

   What is a thunderstorm? Explain the process of its formation from the beginning.

   Hint. Give the whole chain — heating, cloud, charges, flash — not just the last step.

   Definition. A storm accompanied by lightning and thunder is called a thunderstorm.

   Formation, in full:

   Stage 1 — the storm. Land is heated; the warm, moist air rises, creating a low pressure area; cooler air flows in from surrounding high-pressure regions and is heated in turn, setting up a continuous wind circulation. The rising air expands and cools, its moisture condenses into droplets and clouds form. Droplets merge into heavier drops that fall as rain, hail or snow. The strong winds accompanied by rain is called a storm.

   Stage 2 — the charges. Under certain conditions, warm air rises to great heights that the low temperature there converts water droplets into ice particles. Strong winds blowing up and down rub the ice particles and water droplets together, and cause static electric charges to develop within the clouds. Positive ice particles rise to the upper part; negative water droplets stay in the lower part.

   Stage 3 — the flash. Air normally insulates, but when the charge build-up becomes very large the insulating property of air breaks down. A sudden flow of charges gives the flash of lightning, and the air it heats expands to give thunder.

   ✦ A storm becomes a thunderstorm when stages 2 and 3 are added. Every thunderstorm is a storm; not every storm is a thunderstorm. Whether the extra stages happen depends on whether the air rises high enough and cold enough to make ice particles, and whether the up-and-down winds are strong enough to rub them.

   The two requirements, from the Snapshot: moisture and strong winds.

   This is exercise question 11.

6. 64 marksCuriosity Grade 8, Chapter 6, page 91, A step further

   The chapter names several local Indian thunderstorms. List them with their regions and say what they are useful for.

   Hint. Four names and four regions — transcribe them carefully.

   The chapter's list:

   Local name	Region	Timing and use
   Kalboishakhi	West Bengal, Bihar and Jharkhand	Occur before the arrival of the monsoon, thereby helping kharif crops to grow
   Bordoisila	Assam	Same — pre-monsoon, helping kharif crops
   Mango showers	Kerala, Karnataka and Tamil Nadu	They support the ripening of mangoes
   (local thunderstorms)	Karnataka	Help in the growth of coffee plants

   The chapter describes them as isolated and localised thunderstorms that can sometimes occur in various regions of India.

   ✦ Why these names exist at all. They are named because farmers depend on them. A thunderstorm is destructive in general — this chapter spends two pages on the dangers of lightning — yet these particular pre-monsoon storms arrive at the right moment for the kharif sowing, for mangoes to ripen and for coffee to grow. A phenomenon is not simply good or bad; it depends on when and where it lands.

   Stick to what the chapter gives. It names the storms, the states and the crops, and gives no dates, rainfall figures or frequencies. If you want to write about when Kalboishakhi typically occurs or how much rain it brings, take it from a current India Meteorological Department source and cite it — do not supply a number from memory.

7. 74 marksCuriosity Grade 8, Chapter 6, page 91

   What precautions does the chapter give for staying safe during lightning?

   Hint. Reproduce the book's advice exactly — this is safety guidance, not a place to improvise.

   Why precautions are needed. Lightning can be dangerous! It can ignite fires, damage buildings, and cause severe burns or death in humans and animals.

   The chapter's advice, in its own words:

   Advice
   During lightning, stay away from tall objects
   Find a low-lying open area and crouch down, and minimise contact with the ground (Fig. 6.17)
   Do not lie down flat
   Avoid using an umbrella with a metallic rod
   If you are in water, get out of it
   If you are inside a bus or a car, you are comparatively safer

   ✦ Two items in that list are worth reading twice, because they are easy to get backwards.

   • Crouch, do not lie flat. Lying down feels like the safest thing to do and is specifically ruled out, because it puts far more of your body in contact with the ground. Crouching keeps you low and keeps your contact with the ground small.
   • A car is comparatively safer, which is why exercise 2(iv) is true. Note the chapter's careful word comparatively — safer than being out in the open, not guaranteed safe.

   Reproduce this list as the book gives it. Lightning safety is a case where an invented extra rule could genuinely put someone at risk, so do not add advice of your own here, and in real weather follow whatever your local authorities say.

8. 84 marksCuriosity Grade 8, Chapter 6, page 92, Ever heard of ...

   What is a lightning conductor and how does it protect a building?

   Hint. Describe both ends of the rod and what each is for.

   What it is. A lightning conductor is a metallic rod installed along the walls of buildings during their construction.

   Its two ends:

   End	Where it goes	Purpose
   Pointed upper end	Kept higher than the highest point of the building (Fig. 6.18)	It is the highest thing on the building, so a strike reaches it rather than the roof or walls
   Lower end	Buried deep in the ground	Carries the charge safely away into the earth

   How it protects. The rod provides easy path for the transfer of electric charges into the ground. The charge travels down the metal rod, which conducts well, instead of forcing its way through the building's walls, wiring and occupants.

   ✦ The rod does not stop lightning — it gives it somewhere harmless to go. That is the key idea, and it is easy to state wrongly. Nothing about the rod prevents a strike. It offers the charge an easy conducting path to the ground so that the destructive part — ignite fires, damage buildings, cause severe burns — does not happen through the structure.

   Why it is fitted during construction, as the chapter specifies: the rod has to run the whole height of the building and go deep into the ground, which is far easier to do while the walls are being built than afterwards.

   Listed among the Snapshots: Lightning conductors protect buildings from the effects of lightning.

9. 94 marksCuriosity Grade 8, Chapter 6, page 91

   Would lightning occur if air and clouds were good conductors of electricity? Give reasons.

   Hint. Ask what the insulating air is currently doing for the process.

   No, lightning as we know it would not occur.

   The reason, from the chapter's own explanation. Normally, air acts as an electrical insulator and does not let opposite charges meet. But when the build up of charges becomes very large, the insulating property of air breaks down. A sudden flow of charges takes place, producing a bright flash of light called lightning.

   So the insulating air is not an obstacle to lightning — it is a necessary ingredient. It is what allows charge to pile up to an enormous level instead of leaking away.

   If air were a good conductor. Charge would flow away continuously, as fast as the rubbing produced it. No large build-up could ever accumulate, so there would be no sudden breakdown and no brilliant flash — at most a steady, invisible trickle of charge.

   If clouds were good conductors. The charge separation itself would fail. Positive ice particles above and negative droplets below could not stay apart in a conducting cloud; the two regions would neutralise each other as fast as the winds separated them.

   ✦ The general point is worth more than the particular answer. Lightning needs a large charge difference released suddenly, and both of those depend on something holding the charges apart in the meantime. Remove the insulation and you remove the storage; remove the storage and there is nothing left to release.

   And no thunder either. Thunder is the sound of air heated by the flash. No flash, no thunder.

   This is exercise question 6.

Solutions written by the tuition.in editorial team and checked against NCERT Curiosity, Textbook of Science for Grade 8, Chapter 6 'Pressure, Winds, Storms, and Cyclones', book pages 80-97 (hecu106.pdf, 18 pages, Reprint 2026-27), downloaded from ncert.nic.in and read page by page. Every activity number, figure number, quantity and quoted sentence below was checked against that PDF. THREE FIGURES WERE MEASURED, NOT EYEBALLED, because three exercise answers turn on them. Fig. 6.22 (exercise 1(iv)) was rendered at 900 dpi and the vessel walls located from the dark outlines: vessel A is 519 px wide and vessel B is 726 px, so B is 1.40x wider, while the water columns measure 660 px and 671 px - equal to within 1.7%, matching the question's premise of equal levels. Hence P_A = P_B but F_A < F_B, answer (b). Fig. 6.24 (exercise 7) was segmented by colour: the two balloons occupy identical vertical ranges (rows 1260-1403, centroids both at row 1334), so they are at exactly the same height and bulge equally. Fig. 6.25 (exercise 9) was measured by tracking the palm trunks: the leftmost trunk's centre moves from x=655 at the top to x=763 near the base, so the crown sits about 108 px LEFT of the base, and all four crowns stream leftwards - the wind blows from B to A. Since a summer afternoon gives a SEA BREEZE (sea to land), B is the sea and A is the land. Fig. 6.21 was also rendered and confirmed to show the three vessels JOINED BY TUBES near their bases, which is what makes answer (d) correct. The chapter's own atmospheric-pressure figure was checked rather than assumed: 2250 N over 15 cm x 15 cm = 0.0225 m^2 gives 1,00,000 Pa = 1000 hPa = 1000 mb, which sits squarely inside the 994-1008 mb range marked on Fig. 6.19, so the book's number is internally consistent. Two deliberate restraints. (1) The chapter names exactly ONE cyclone (Amphan 2020, peak winds 270 km/h) and one surge range (3-12 m), and gives no cyclone categories, no casualty figures, no monsoon rainfall percentages and no atmospheric composition percentages. None are supplied here; the research projects tell the student to cite IMD or an equivalent checked source and to report disagreement between sources rather than pick a number. (2) Lightning-safety advice is reproduced exactly as the book gives it, with nothing added, since an invented extra rule could put someone at risk.. Questions are referenced from the NCERT textbook for identification.