GK (Science)

Water is considered an anomalous compound because it exhibits anomalous expansion - it expands (becomes less dense) when it freezes at 0°C, unlike most other substances which contract on solidification. This unique property is crucial for aquatic life survival in winter.

Power is defined as the rate of energy transfer or work done per unit time. The formula is P = E/t. Here, Energy = 20 joules, Time = 5 seconds. Therefore, Power = 20/5 = 4 watts. Option D is correct.

The sun and earth are separated by vacuum (space). Heat cannot be transferred by conduction (requires medium) or convection (requires fluid medium) in vacuum. The only mode of heat transfer possible through vacuum is radiation, which travels as electromagnetic waves (infrared, visible light). Therefore, heat from sun reaches earth by radiation alone.

In simple harmonic motion, total energy E = 1/2 k A^2 where k is force constant and A is amplitude. The energy is directly proportional to the SQUARE of amplitude, not amplitude itself or its cube. This is because both potential energy (at extremes) and kinetic energy (at mean position) depend on A^2.

An electric motor works on the principle that a current-carrying conductor in a magnetic field experiences a force. It takes electrical energy as input and produces mechanical energy (rotational motion) as output. This is the opposite of a generator, which converts mechanical energy to electrical energy.

For a floating body, the fraction submerged equals the ratio of densities: fraction_submerged = density_iceberg / density_water. Here: 0.93/1.03 = 0.9029, meaning about 90.29% is submerged. The visible (above water) fraction is 1 - 0.9029 = 0.0971 or 9.71%, which rounds to approximately 11%. Option B is closest.

The National Chemical Laboratory (NCL) is a premier research institution located in Pune, Maharashtra. It was established in 1950 and is one of India's foremost laboratories in the field of chemical sciences.

N-type semiconductors are created by doping pure semiconductor materials like germanium or silicon with pentavalent impurities (elements with 5 valence electrons like phosphorus, arsenic, or antimony). These impurities donate extra electrons for conduction, hence 'n' for negative charge carriers.

In uniform circular motion, the speed is constant but velocity continuously changes direction. This change in velocity toward the center creates centripetal acceleration - constant in magnitude (v²/r) and always directed radially inward toward the center of the circle.

One micron (micrometer) equals one millionth of a meter, or 10^-6 meters. The prefix 'micro-' in the metric system denotes 10^-6, just as 'milli-' denotes 10^-3 and 'nano-' denotes 10^-9.

The average distance from Earth to the Sun is approximately 150 million kilometers (about 93 million miles). This distance is defined as one Astronomical Unit (AU), which is used as a standard measurement for distances within our solar system.

The normal human body temperature is approximately 37°C (98.6°F), though it can vary slightly between individuals and throughout the day. This is the temperature at which human biological processes function optimally.

Helium is the preferred gas for modern balloons and airships because it is non-flammable and inert. Hydrogen, while more buoyant, is extremely flammable and dangerous (as demonstrated by the Hindenburg disaster). Helium provides safe lift with only slightly less buoyancy.

The Sun's energy is produced by nuclear fusion of light nuclei - specifically, hydrogen nuclei (protons) fusing to form helium in the core. This process releases enormous energy because the mass of helium produced is slightly less than the mass of four hydrogen nuclei, with the difference converted to energy (E=mc²).

Electromotive force (EMF) is work done per unit charge, so its dimensional formula is [Work]/[Charge] = [ML²T⁻²]/[Q] = ML²T⁻²Q⁻¹. This is the same dimension as voltage or potential difference.

Escape velocity depends on mass and radius: v = √(2GM/R). Earth's higher mass-to-radius ratio gives it an escape velocity of about 11.2 km/s, while the Moon's is only about 2.4 km/s. The Moon's lower gravity means less speed is needed to overcome it.

Lead is commonly used for containers holding strong acids because it forms an insoluble protective layer of lead sulfate on contact with sulfuric acid, preventing further reaction. Platinum is also acid-resistant but prohibitively expensive. Copper and brass readily react with acids.

Tritium (hydrogen-3 or ³H) is a radioactive isotope of hydrogen consisting of one proton and two neutrons in its nucleus. It is the heaviest naturally occurring hydrogen isotope, with deuterium (²H) having one proton and one neutron, and protium (¹H) having just one proton.

Na2CO3.10H2O is the correct formula for washing soda (sodium carbonate decahydrate). This is different from soda ash (anhydrous Na2CO3) or the monohydrate form. The 10 water molecules are chemically bound in the crystal structure, which gives washing soda its characteristic properties.

The frequency of light remains constant when it passes from one medium to another because it's determined by the source. However, the wavelength decreases in glass because light travels slower in the denser medium (v = f×λ, and n=c/v). The relationship is: λ_glass = λ_air / n_glass.

In zeolite water softening, sodium ions (Na+) from the zeolite exchange with calcium and magnesium ions (Ca2+, Mg2+) in hard water. The zeolite releases Na+ and traps Ca2+/Mg2+ ions. This process removes hardness ions that cause scaling. Option B correctly identifies Na+ and Mg2+ as involved in the exchange.