Current Affairs MCQs – Page 49 (Q481-490)

The chemical symbol for potassium is K, derived from the Latin word kalium, itself derived from an Arabic word for the ashes of certain plants from which the element was historically extracted. Potassium has an atomic number of 19 and is a highly reactive alkali metal essential for numerous biological functions, including nerve signaling and muscle contraction in humans. P, Po and Pt are tempting distractors, with P actually representing phosphorus, Po representing polonium, and Pt representing platinum, all easily confused with potassium's less obvious symbol. Bananas are commonly cited as a dietary source rich in potassium, though many other foods contain even higher concentrations.

Hydrogen is the lightest chemical element in the periodic table, with an atomic number of 1 and consisting of just a single proton and electron in its most common form. It is also the most abundant element in the universe, making up the vast majority of stars, including the Sun, through nuclear fusion reactions. Lithium, helium and carbon are tempting distractors, with helium being the second-lightest element, immediately following hydrogen in atomic number and abundance. Hydrogen is increasingly being explored as a clean energy source, particularly for fuel cells in vehicles and industrial applications.

Hydrogen is the element with atomic number 1, meaning each of its atoms contains a single proton in its nucleus, making it the simplest and lightest element on the periodic table. It exists most commonly as a diatomic gas, H2, and plays a central role in the nuclear fusion reactions that power stars, including our Sun. Helium, carbon and oxygen are tempting distractors, with helium holding atomic number 2, immediately following hydrogen. Hydrogen was first identified as a distinct element by English scientist Henry Cavendish in 1766, though it had been observed by earlier chemists without being properly characterized.

Diamond is the hardest naturally occurring substance known, composed of carbon atoms arranged in an extremely strong crystal lattice structure that gives it exceptional resistance to scratching. Its hardness is measured at 10 on the Mohs scale of mineral hardness, the maximum possible rating on that scale. Granite, quartz and titanium are tempting distractors, as each is a hard material used in construction or industry, but none approaches diamond's extreme hardness. Diamonds are prized both for jewelry, due to their brilliance and rarity, and for industrial uses like cutting and grinding tools.

Newton's first law of motion is also commonly known as the law of inertia, stating that an object at rest stays at rest and an object in motion stays in motion at a constant velocity unless acted upon by an external force. This principle fundamentally challenged earlier Aristotelian ideas that objects naturally tend to come to rest without a continued push. Law of gravity, law of acceleration and law of reaction are tempting distractors, with law of acceleration and law of reaction actually corresponding to Newton's second and third laws respectively. Newton published all three laws of motion together in his landmark 1687 work, Philosophiae Naturalis Principia Mathematica.

Archimedes' principle primarily explains the buoyancy of objects in fluid, stating that the upward buoyant force exerted on a submerged or partially submerged object is equal to the weight of the fluid the object displaces. According to legend, the ancient Greek mathematician Archimedes discovered this principle while bathing and famously ran through the streets shouting Eureka in excitement. Magnetic fields, electric current and speed of light are tempting distractors, as each is a different physical phenomenon entirely unrelated to Archimedes' work on fluids. The principle remains fundamental to shipbuilding, submarine design and understanding why objects float or sink.

Boyle's Law describes the inverse relationship between the pressure and volume of a gas at constant temperature, stating that as the volume of a gas decreases, its pressure increases proportionally, and vice versa. The law was formulated by Anglo-Irish scientist Robert Boyle in 1662 based on his experiments with gases trapped in a J-shaped tube. Temperature and mass, volume and mass, and density and temperature are tempting distractors, as each describes a different relationship not captured by Boyle's specific gas law. Boyle's Law is one of several gas laws, alongside Charles's Law and Gay-Lussac's Law, that together form the ideal gas law.

Ohm's Law describes the relationship between voltage, current and resistance in an electrical circuit, stating that voltage equals current multiplied by resistance, a fundamental equation used throughout electrical engineering and physics. The law was formulated by German physicist Georg Simon Ohm in 1827, based on his experiments measuring current flow through various conductors. Capacitance, frequency and power are tempting distractors, as each is a different electrical property not directly described by Ohm's specific law. The ohm, the SI unit of electrical resistance, is named in his honor.

The Pythagorean theorem is a fundamental principle in geometry, stating that in a right triangle, the square of the length of the hypotenuse equals the sum of the squares of the lengths of the other two sides. It is attributed to the ancient Greek mathematician Pythagoras, though evidence suggests the relationship was known to earlier civilizations, including the Babylonians, well before his time. Biology, astronomy and chemistry are tempting distractors, as each is a distinct scientific field unrelated to this specific geometric principle. The theorem remains one of the most widely taught and applied results in all of mathematics, with hundreds of known distinct proofs.

Gregor Mendel, an Austrian monk and scientist, is often referred to as the Father of Genetics for his groundbreaking experiments on pea plants in the 1860s, which revealed the basic patterns of inheritance through what became known as Mendel's laws. His careful, statistical approach to breeding experiments identified dominant and recessive traits, concepts still fundamental to genetics today. Louis Pasteur, Charles Darwin and Carl Linnaeus are tempting distractors, as each made other major but separate contributions to microbiology, evolutionary theory and biological classification respectively. Mendel's work was largely overlooked during his lifetime and only gained widespread recognition decades later, in the early 20th century.