Lightening

CloseWhen two objects are rubbed together, electrons can transfer from one object to the other. One object becomes negatively charged (gains electrons) and the other becomes positively charged (loses electrons). This is called charging by friction or charging by rubbing.

CloseThere are only two types of electric charges in nature: positive charge and negative charge. Protons carry positive charge, and electrons carry negative charge. All other charged objects have an excess or deficit of these basic charges.

CloseTwo objects with the same type of charge (both positive or both negative) push each other away. This is called repulsion. For example, two negatively charged balloons will move apart from each other.

CloseTwo objects with opposite charges (one positive and one negative) pull toward each other. This is called attraction. For example, a positively charged glass rod attracts a negatively charged plastic ruler.

CloseWhen glass is rubbed with silk, electrons move from the glass rod to the silk cloth. The glass rod loses electrons and becomes positively charged. The silk cloth gains electrons and becomes negatively charged.

CloseWhen plastic (or ebonite) is rubbed with wool, electrons move from the wool to the plastic rod. The plastic rod gains extra electrons and becomes negatively charged. The wool loses electrons and becomes positively charged.

CloseAn electroscope is a simple instrument used to detect electric charge. It usually consists of a metal rod with two thin metal leaves (often made of gold or aluminium) inside a glass container. When a charged object touches the rod, the leaves spread apart.

CloseWhen a charged object touches the metal disc, the charge spreads down to the two metal leaves. Both leaves get the same type of charge (both positive or both negative). Like charges repel, so the leaves push apart and diverge.

CloseIf the leaves collapse, it means the charge on the electroscope is being neutralised. This happens when an object with opposite charge is brought near. Opposite charges attract, so the charge from the electroscope is pulled away, reducing the repulsion between the leaves.

CloseDuring a thunderstorm, water droplets and ice particles rub against each other inside clouds. This rubbing causes separation of charges. The upper part of the cloud becomes positively charged, and the lower part becomes negatively charged. When the charge becomes large enough, it discharges as lightning.

CloseDue to the movement and collision of ice particles and water droplets inside the cloud, the heavier, lower part of the cloud accumulates negative charge. The upper part becomes positively charged. The ground below also becomes positively charged by induction.

CloseLightning is a massive electric discharge. When the voltage between the cloud and the ground (or between two clouds) becomes extremely high, air breaks down and becomes a conductor. A huge current (flow of electrons) passes through the air, producing intense light and heat.

CloseA building (especially with lightning protection) or a metal car (which acts as a Faraday cage) is safe during lightning. The metal body of the car conducts the lightning around the outside, protecting the people inside. Trees, open ground, and metal objects are dangerous.

CloseA lightning conductor is a metal rod (usually copper) fixed at the highest point of a building. It is connected by a thick metal wire to a metal plate buried deep in the ground. If lightning strikes, the conductor safely passes the electric charge to the ground, protecting the building.

CloseCopper is an excellent conductor of electricity. It allows the huge current from a lightning strike to pass through it easily into the ground. Other good conductors like aluminium are also used, but copper is most common.

CloseThe Earth’s outer layer (crust) is made of large pieces called tectonic plates. These plates are slowly moving. Sometimes they get stuck at their edges due to friction. When the stress becomes too great, they suddenly slip, releasing enormous energy in the form of seismic waves. This causes the ground to shake — an earthquake.

CloseThe focus is the actual underground location where the rocks first break and slip, releasing energy. The epicentre is the point on the Earth’s surface directly above the focus. The focus is deep inside the Earth; the epicentre is on the surface.

CloseThe epicentre is the point on the ground surface that is directly above the focus. The strongest shaking usually occurs at or near the epicentre. News reports often give the epicentre location (e.g., 50 km north of a city).

CloseA seismograph is a sensitive instrument that detects and records the vibrations (seismic waves) caused by an earthquake. It produces a graph called a seismogram. The size of the waves on the seismogram helps determine the earthquake’s magnitude.

CloseThe Richter scale is a numerical scale (from 1 to 10) that measures the magnitude of an earthquake based on the amplitude of seismic waves. Each whole number increase represents about 32 times more energy released. An earthquake of magnitude 6 is much stronger than magnitude 4.

CloseDuring an earthquake, falling objects and collapsing structures are the main dangers. Taking cover under a sturdy table protects you from falling debris. The “Drop, Cover, and Hold On” method is recommended: drop to the ground, take cover under something strong, and hold on until shaking stops.

CloseOutdoors, the greatest danger is falling objects like bricks, glass, branches, or electric poles. An open field or park is safest. Stay away from buildings, streetlights, utility wires, and trees. Drop to the ground and cover your head.

ClosePull over to a clear spot away from buildings, trees, overpasses, and power lines. Stay inside the vehicle with your seatbelt fastened. The car can protect you from some falling objects. After the shaking stops, drive carefully and avoid damaged roads.

CloseEarthing means providing a path for electric charge to flow into the Earth. The Earth is large and electrically neutral, so it can accept or supply charge without changing its potential. Lightning conductors work by earthing the charge safely.

CloseInduction is the process of charging a neutral object by bringing a charged object near it without touching. The charged object attracts opposite charges and repels like charges in the neutral object. The leaves get a temporary charge and diverge. When the charged object is removed, the leaves collapse.

CloseThe human body is a conductor. When you touch a charged object, the excess charge flows through your body to the ground (Earth). This is why a charged balloon slowly loses its charge when you hold it — your body provides a path to Earth.

CloseTrees are often the tallest objects in an open area, and lightning tends to strike the highest point. Also, trees contain water and sap, which are conductors. When lightning strikes a tree, the current can jump to a person standing nearby or the tree can explode from the heat.

CloseLandline phones are connected by wires that can conduct lightning strikes from outside into your home. Cordless phones and mobile phones are safer because they are not physically connected to outdoor wires. Avoid using any wired appliance during a thunderstorm.

CloseElectrons carry negative charge. If an object loses electrons, it has more protons than electrons, so it becomes positively charged. The object that gains electrons becomes negatively charged. The total charge is conserved — it is just transferred from one object to the other.

CloseA lightning conductor (lightning rod) provides a safe path for lightning current to travel directly to the ground. It prevents the lightning from passing through the building’s structure, which could cause fire, explosion, or structural collapse. The conductor must be properly earthed.

CloseThe Earth’s crust is the thin, solid outermost layer. It is broken into tectonic plates. Most earthquakes occur in the crust because it is brittle and can fracture. The mantle below is partly molten, and the core is very hot and under extreme pressure.

CloseFault lines are cracks or boundaries between tectonic plates. Most earthquakes happen along these fault lines because the plates are constantly moving, grinding against each other, or pulling apart. Examples include the San Andreas Fault in California.

CloseIf you are already in bed, stay there. Use a pillow to protect your head and face from falling objects or broken glass. Do not run through a dark, shaking room where you could trip or be hit by falling items. Hold on to the bed frame.

CloseAn earthquake is the shaking of the Earth’s surface caused by the sudden release of energy in the Earth’s crust. This energy travels as seismic waves. Earthquakes can last from a few seconds to several minutes and can cause immense damage.

CloseA tsunami is a series of huge ocean waves caused by underwater earthquakes, volcanic eruptions, or landslides. The earthquake displaces a large volume of water. Tsunamis can travel at high speeds and cause severe flooding and destruction when they reach coastlines.

CloseHeavy rainfall can cause landslides and floods, but it does not cause earthquakes. Earthquakes are caused by geological processes: movement of tectonic plates, volcanic activity, and sometimes human activities like large underground explosions or reservoir-induced seismicity.

CloseIn crowded places, running can cause panic and stampede. Instead, drop to the ground, take cover under a sturdy object (like a table or seat), protect your head and neck, and stay away from shelves (which may fall) and windows (which may shatter). Move out only after shaking stops.

CloseAn electroscope can detect whether an object is charged or not. By bringing a charged object near it, we can also determine the type of charge (positive or negative) by observing whether the leaves diverge more or collapse. However, it does not measure the exact quantity of charge.

CloseWhen a negatively charged rod touches the disc, some negative charge (electrons) transfers to the electroscope. Both metal leaves now have an excess of negative charge. Like charges repel, so the leaves push apart and diverge.

CloseIf no sturdy table is available, move to an interior wall (away from windows, exterior walls, and heavy furniture). Sit or kneel on the floor, cover your head and neck with your arms and hands, and bend forward to protect vital organs. Interior walls are less likely to collapse.

CloseAny building that is tall or located in an open area is at risk of lightning strikes. A lightning conductor provides a safe path to ground. In many regions, building codes require lightning protection for tall structures, hospitals, schools, and public buildings.

CloseInduction occurs when a charged object is brought near a neutral conductor. The charges in the conductor rearrange themselves. Opposite charges are attracted to the near side, and like charges are pushed to the far side. The conductor remains neutral overall, but has separated charges.

CloseScientists cannot predict the exact date, time, or location of an earthquake. However, we can identify high-risk seismic zones and take safety measures like building earthquake-resistant structures, conducting drills, and preparing emergency kits.

CloseMobile phones are wireless devices. They do not have a physical wire connecting them to the outside electrical network. Therefore, lightning cannot travel through a mobile phone from outside. However, avoid charging your mobile phone during a thunderstorm because the charger is wired to the mains.

CloseA homemade electroscope can be made by inserting a metal hook through a cork in a glass jar. Two thin strips of aluminium foil are hung from the hook. When a charged object touches the hook, the foil strips diverge. The glass bottle insulates the leaves from outside charges.

CloseEarthing provides a safe path for excess charge to flow into the Earth. This neutralises the object. Lightning conductors work by earthing. Also, electrical appliances have a third pin (earth pin) for safety, so that if a fault occurs, the current goes to Earth instead of through a person.

CloseIf you cannot reach an open area, move close to a building wall and lie flat. Cover your head and neck. However, this is less safe than an open area because debris can fall from the building. Stay away from glass windows and overhead fixtures.

CloseLightning can heat the surrounding air to around 30,000 degree Celsius, which is five times hotter than the surface of the sun. This extreme heating causes the air to expand explosively, producing the sound wave we hear as thunder.

CloseUnder a sturdy table or desk is the safest because it protects you from falling objects like ceiling fans, light fixtures, and debris. The “triangle of life” method is not recommended by most disaster agencies. “Drop, Cover, and Hold On” under a sturdy object is the standard advice.

CloseBefore an earthquake, you should prepare your home: fasten tall furniture to wall studs, place heavy objects on lower shelves, know how to turn off gas and electricity, keep emergency supplies (water, food, torch, first aid kit), and practice drop-cover-hold drills with your family.