General Science Mixed Quiz: Set 142

The SI unit of inductance is the henry, symbol H, named after the American scientist Joseph Henry. Inductance measures how strongly a coil opposes a change in the current through it by producing an induced emf.

Palaeontology is the study of fossils, the preserved remains or traces of organisms of past geological ages, and it supplies the evidence on which the history of life and the theory of evolution rest.

Zero on the Kelvin scale lies 273.15 degrees below the freezing point of water. The Kelvin and Celsius scales have degrees of the same size, so T(K) = t(°C) + 273.15.

Red blood cells are produced in the red bone marrow, lose their nucleus on maturing and survive roughly four months, after which they are broken down in the spleen, which is accordingly called the graveyard of red blood cells; the iron released from their haemoglobin is used again.

Light from an object at the centre of curvature strikes a concave mirror along its radius, so it returns along the same path and forms the image at the same point.

In 1897 Thomson passed an electric discharge through a gas at very low pressure and showed that the cathode rays produced were a stream of identical negatively charged particles, far lighter than any atom and the same whatever gas or electrode was used.

Reverberation is the lingering of sound in a closed space caused by many reflections from the walls, ceiling and floor.

An alpha particle takes away two protons and two neutrons, so the parent loses four units of mass number and two units of atomic number and becomes an element two places earlier in the periodic table; uranium-238, for instance, becomes thorium-234.

A split-ring commutator reverses the coil's connection to the outer circuit every half turn, so the current outside flows in one direction only.

An n-type semiconductor is made by doping with a pentavalent element, that is one with five valence electrons, such as phosphorus, arsenic, antimony or bismuth.

The element with atomic number 35 is bromine, whose 35 electrons are arranged as 2, 8, 18, 7, leaving seven in the outermost shell.

In this zone the supply of air is unrestricted, so combustion is complete and all the carbon of the fuel is converted to carbon dioxide, releasing the maximum heat.

Nitrogen dioxide has an unpaired electron, so two of its molecules join to form dinitrogen tetroxide, N 2 O 4.

Bakelite is made by condensing phenol with formaldehyde, and on moulding its chains join to one another by strong covalent cross-links into a single rigid network.

It is a carbon compound with a carboxyl group, so it is an organic acid. Acetic acid (ethanoic acid, CH₃COOH) contains the –COOH group typical of carboxylic acids.

The ovum released at ovulation is picked up by the fimbriae of the infundibulum and meets the sperm in the ampulla, the wide middle part of the tube, where fusion takes place to form the zygote.

The reaction happens because iron is more reactive than copper and pushes it out of its salt, so statement C is false.

Acetic acid boils far above methane, and ethanol gives hydrogen with sodium, while statements 1 and 4 are false. Propyne (CH3–C≡CH) is an alkyne: it has one carbon–carbon triple bond and no double bonds, so statement 1 is wrong.

Nettle stings contain methanoic (formic) acid, so statement I is right, while statements II and III name the wrong compounds.

Mitochondria have their own DNA and their own ribosomes, so they can make some of the proteins they need. Mitochondria are the "powerhouses of the cell", where food is broken down in aerobic respiration to release energy stored as ATP.