A flash of lightning and the spark from a doorknob after walking on carpet are caused by exactly the same thing — static electricity, just at a vastly different scale.
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Lightning is nature's way of neutralising a huge build-up of electric charge between clouds and the ground.
📌 How charge behaves
Like charges repel, unlike charges attract — this single rule explains every electrostatic effect.
Charging by rubbing: friction transfers electrons from one object to another, leaving one positively and one negatively charged.
An electroscope detects the presence of charge by the way its leaves diverge (spread apart) when a charged object comes near.
A lightning conductor is a metal rod on a tall building, connected to the ground by a thick wire. It gives lightning an easy, safe path to Earth, protecting the rest of the building from a direct, damaging strike.
An earthquake releases energy that travels outward as waves — and different types of these waves travel at different speeds.
📊 Seismic waves
| Wave type | Speed | What it does |
|---|---|---|
| P-waves (Primary) | Fastest — arrive first | Push-pull motion, can travel through solids and liquids |
| S-waves (Secondary) | Slower — arrive second | Side-to-side motion, travel only through solids |
| Surface waves | Slowest | Cause most of the destructive shaking at the surface |
Precaution during an earthquake: the recommended action is "Drop, Cover, and Hold On" — get under sturdy furniture, away from windows and heavy objects that could fall.
The planets don't just orbit the Sun in any order — their arrangement, and the reasons behind eclipses, follow predictable rules.
✨ Two kinds of eclipse
Solar eclipse
Moon between Sun and Earth
Happens only on a new moon day, when the Moon blocks sunlight from reaching Earth.
Lunar eclipse
Earth between Sun and Moon
Happens only on a full moon day, when Earth's shadow falls on the Moon.
Pro tip: An eclipse does not happen every new moon or full moon because the Moon's orbit is slightly tilted compared to Earth's orbit around the Sun — the three bodies must line up almost exactly for an eclipse to occur.
12 NSO-pattern questions on natural phenomena and the solar system, including two Achievers-level questions.
