Gen Studies (Electricity and Magnetism)

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He found that a metal rod from the top to the bottom of a building makes the flow of lightning harmlessly pass through.

Choke coil works as an inductor and creates high voltage needed for ionization of gases in the tube. For the tubelight to glow, gases present in the tube should be ionized which requires high voltage, but the supply at domestic level is only around 220 V. The starter switches on and off the current through choke coil, which helps to build high transient voltage around choke coil.

Live wire is the wire with red covering.

In India and many countries, the standard household AC supply voltage is 220V at 50Hz. This is the RMS (Root Mean Square) voltage. Some countries use 110V or 240V, but 220V is the most common international standard outside North America.

Rectifiers are circuits made of diodes and are used to convert AC to DC. 

Rubber, wood, glass and porcelain are the best insulators.

Ferromagnetic materials like iron, nickel, and cobalt can be magnetized very strongly because their atomic magnetic moments align parallel to each other, creating a strong net magnetic field. Diamagnetic materials are weakly repelled by magnetic fields and cannot be permanently magnetized. Paramagnetic materials are weakly attracted but much less so than ferromagnetic ones. Option D is incorrect because diamagnetic materials cannot be magnetized to any significant extent.

Nichrome (nickel-chromium alloy) is the standard material for heating elements because it has high electrical resistance, can withstand temperatures over 1000°C without oxidizing, and maintains structural integrity when heated repeatedly. Tungsten has a very high melting point but is used in incandescent bulb filaments, not heating elements. Pure iron would oxidize and rust quickly at high temperatures. Chromium alone is not used for heating elements - it's the chromium in nichrome that provides corrosion resistance.

Dry air is an insulator.

The fuse wire must be placed in the live wire so that when it melts due to excess current, it disconnects the power supply from the appliance completely. If the fuse were in the neutral wire, the appliance would remain connected to live voltage even when the fuse blows, creating a serious shock hazard. The earth wire is for safety grounding and never carries current during normal operation. Placing the fuse in the neutral wire defeats the entire safety purpose of the fuse.

Nitrogen is filled in bulbs. Argon is another noble gas and is used to keep light bulb filaments from burning away. Since argon is non-reactive, it is filled in a light bulb instead of regular air, which contains oxygen that can cause a burning reaction when exposed to the thin metal filaments found in light bulbs. Other noble gases include krypton, xenon and radon.

Silver is the best natural conductor of electricity among all elements - even better than copper and gold. This is why it's used in high-performance electrical contacts and specialized applications. Glass, ebonite, and rubber are all insulators - they have very high electrical resistance and do not allow current to flow through them easily. Ebonite is specifically a hardened rubber designed to be an excellent insulator.

 A bird sitting on a high power line is not affected practically as there is no short circuit.