General Science Mixed Quiz: Set 153

In parallel the equivalent resistance is always smaller than the smallest single resistor, so here it falls below 1 Ω. For resistors in parallel, 1/R = 1/R1 + 1/R2 + 1/R3 = 1/1 + 1/2 + 1/3 = 11/6, so R = 6/11 Ω, about 0.55 Ω. Each extra parallel…

Seismology is the study of earthquakes and of the passage of seismic waves through the earth, and it is from seismic wave records that the layered structure of the interior of the earth has been worked out; the instrument used is the seismograph.

Fullerenes are made of carbon atoms alone, with no surface to trap other substances, so they are counted as the purest form of carbon.

Vulcanisation is the heating of raw rubber with sulphur, which forms short cross-links between the long isoprene chains. Raw rubber is soft, sticky when warm and brittle when cold; the vulcanised product is strong, far more elastic and stable over a wide range of temperature.

EDTA is a hexadentate ligand: one EDTA ion binds a metal ion through six donor atoms, so it forms complexes with coordination number 6.

Mycoplasmas are the smallest living cells known, they lack a cell wall altogether, and because of that they can change shape and are not affected by antibiotics that act on the wall; they cause diseases in plants and animals and are placed in the kingdom Monera.

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

The adult skeleton has eighty bones in the axial part, that is the skull with the ear ossicles and hyoid, the vertebral column, the ribs and the sternum, and one hundred and twenty-six in the appendicular part, that is the limbs with the pectoral and pelvic girdles, making two hundred…

Bacteria and fungi grow on artificial media, but viruses multiply only inside living cells. Bacteria and fungi are living cells with their own machinery for making energy and proteins, so they grow on nutrient agar, broth or synthetic media in a laboratory.

The correct answer is A, Karl Landsteiner, the Austrian physician who found in 1900 that human blood falls into groups according to the antigens on the red cells, which made safe transfusion possible, and who received the Nobel Prize in Physiology or Medicine for it in 1930; with Wiener he…

. Oral contraceptive pills prevent pregnancy mainly by stopping the ovary from releasing an egg.

The system comes from a defence mechanism of bacteria against viruses: a guide RNA takes the Cas9 protein to a chosen sequence in the DNA, Cas9 cuts both strands there, and the cell's own repair machinery then changes the sequence, so a gene can be switched off or corrected in…

All three follow from Einstein's General Theory of Relativity, published in 1915. General relativity explains gravity not as a force but as the curving of space-time by mass and energy; in John Wheeler's words, matter tells space-time how to curve, and space-time tells matter how to move.

Melanin absorbs the ultraviolet rays of sunlight and shields the DNA of skin cells from damage. Melanin is made by cells called melanocytes in the lower layer of the epidermis.

When calcium carbide reacts with water it gives acetylene (ethyne) gas and calcium hydroxide, not hydrogen. The reaction CaC₂ + 2H₂O → C₂H₂ + Ca(OH)₂ is the old method of making acetylene, once burnt in miners' lamps and still used for welding and for ripening fruit illegally.

Balance is controlled by the inner ear, which holds the vestibular apparatus alongside the organ of hearing. It is made of three semicircular canals set at right angles to one another and two small sacs, the utricle and the saccule.

In every real machine some of the work put in is used in overcoming friction between the moving parts and in lifting the parts of the machine itself, and that work leaves the system as heat and sound, so the work delivered to the load is always less than the…

Cholera is caused by the bacterium Vibrio cholerae and spreads through water and food contaminated with faecal matter, which is why it breaks out after floods and wherever sewage mixes with the water supply; typhoid, hepatitis A, dysentery and polio spread the same way.

The iris is the coloured ring in front of the lens, formed by the front part of the choroid, and the muscles in it widen or narrow the pupil so that the right amount of light reaches the retina; in dim light the pupil opens wide and in bright light…

Halophytes are plants of saline soils, chiefly the mangroves of tidal creeks and deltas such as Rhizophora and Avicennia, and their morphology is shaped by that habitat: they bear pneumatophores, negatively geotropic breathing roots that rise out of the waterlogged mud, along with stilt and prop roots for support and…