General Science Previous Year Questions (PYQ) with Answers – Page 64

Denisovans were an archaic group of humans, close relatives of the Neanderthals, first identified in 2010 from a finger bone found in Denisova Cave in the Altai Mountains of Siberia.

For an astronomical telescope in normal adjustment the magnifying power equals the focal length of the objective divided by that of the eyepiece, so the eyepiece focal length is 50 ÷ 25 = 2 cm.

A light year is the distance that light travels through a vacuum in one year, so despite the word year it measures length, not time.

The magnetic field inside a long solenoid is B = μ₀nI, where n is the number of turns per unit length and I is the current, so the field depends on these two and not on the diameter.

Electromagnetic waves need no medium, so they travel through vacuum, and they consist of electric and magnetic fields that oscillate at right angles to each other and to the direction of travel.

Wire B has half the resistance of wire A, and at the same voltage power is V²/R, so B dissipates twice the power: P₁ = 2P, which means P = P₁/2.

The body falls freely from rest through 50 m, so v² = 2gh = 2 × 9.8 × 50 = 980, giving v = √980, about 31.3 m s⁻¹; its total energy at release is all potential energy, mgh = 2 × 9.8 × 50 = 980 J. Because the…

Ultrasound is sound with a frequency above 20,000 hertz, the upper limit of human hearing, so its defining feature is a higher frequency than audible sound.

Scurvy is caused by a lack of vitamin C, or ascorbic acid, which the body needs to make collagen, the protein that holds skin, gums and blood vessels together.

This is false because viruses have no chlorophyll, no cell organelles and no metabolism of their own, so they cannot make food in any way.

Salmonella typhi is a rod-shaped bacterium that causes typhoid fever in human beings. Typhoid spreads through food and water contaminated with the faeces of an infected person.

. Thyroxine sets the body's basal metabolic rate, that is, how fast cells use oxygen and food to release energy.

Temperature is a measure of the average kinetic energy of the particles of a substance, in a solid as in a gas: in a solid the particles are held in fixed positions but vibrate about them, and heating makes the vibrations faster and wider, so the average kinetic energy rises…

Methane makes up the largest share of biogas, usually about 55 to 75 per cent, and it is the gas that burns.

Zinc gives up electrons most readily, copper less so and silver least, so the order of electron-releasing tendency is Zn > Cu > Ag.

The centrifugal force has the same magnitude as the centripetal force, which for a body moving in a circle is the mass multiplied by the square of the angular velocity multiplied by the radius.

Friction is defined as the force that opposes the relative motion, or the tendency of relative motion, between two surfaces in contact; it acts along the surfaces and always against the direction of motion.

Hydrated oxalic acid has a molar mass of 126 and is a dibasic acid, so its equivalent weight is 126 ÷ 2 = 63.

Iodine exists as diatomic molecules, I₂, in which two iodine atoms share a pair of electrons; so its atomicity is two, not one.

In 1905 Einstein explained the photoelectric effect by treating light as made of packets of energy, later called photons, and he received the 1921 Nobel Prize in Physics for this work.