General Science Mixed Quiz: Set 84

One kilowatt-hour is the energy used by a 1 kW appliance running for one hour: 1000 W × 3600 s = 3.6 × 10⁶ J. The joule is too small for household bills, so electricity companies charge in kilowatt-hours, commonly called units.

A beam seen from the side is visible only because tiny particles send some of its light sideways. Light travelling in a straight line cannot enter our eyes unless something redirects it towards us.

Work done by gravity depends only on the difference in potential between the two points, and here that difference is zero.

Rotational kinetic energy is ½Iω², and the ring has the larger moment of inertia. For a thin ring about the axis through its centre and perpendicular to its plane, all the mass sits at distance R, so I = MR².

The sound travels to the cliff and back in 5 s, so it covers 340 × 5 = 1,700 m in all, and the cliff is half of that, 850 m away.

One parsec equals about 2,06,265 astronomical units, which rounds to 2 × 10⁵ A.U.

On the magnetic equator the angle of dip is zero, so the Earth's magnetic field there is entirely horizontal. The Earth behaves like a huge bar magnet.

Together the two resins take out every dissolved ion, which leaves demineralised water. In the cation exchange resin (written RH), metal ions such as Ca2+, Mg2+ and Na+ are swapped for H+ ions.

The element with atomic number 8 is oxygen, which gains two electrons to complete its octet and forms sodium oxide, Na₂O. Oxygen's electrons are arranged as 2, 6, so it needs two more to reach the stable arrangement 2, 8 of neon.

Both kinds of radiation carry energy that food absorbs as heat, and both are used in everyday kitchens. Infrared radiation is the heat radiation given out by hot bodies: a grill, a toaster, an oven element or glowing coals cook the surface of food mainly by infrared rays.

Photosynthesis absorbs energy from sunlight to build glucose, so it is an endothermic process. An endothermic process takes in heat or light from its surroundings, while an exothermic one gives energy out.

Pinctada margaritifera is the black lip pearl oyster, a bivalve mollusc of the warm shallow water of the Indo-Pacific, where it fastens itself to coral reefs by strong threads.

The stinging hairs of the nettle inject methanoic acid, also called formic acid, which causes the burning pain. Nettle is a herbaceous plant whose leaves carry fine, brittle hairs.

Pliers and scissors are each made of two arms joined at one rivet, and each arm is a complete class 1 lever, so the tool is called a double lever.

Tropolone is aromatic, but its seven-membered ring is made only of carbon atoms, so it is not heterocyclic. A heterocyclic compound has at least one atom other than carbon, such as oxygen, sulphur or nitrogen, inside its ring.

The pinna is the outer, visible flap of the ear, and its funnel shape collects sound from the surroundings. Sound gathered by the pinna travels down the ear canal to the tympanic membrane, or eardrum, which starts to vibrate.

Methanol (CH3OH) is called wood spirit or wood alcohol because it was first obtained by the destructive distillation of wood.

Mitochondria carry their own circular DNA and their own ribosomes, so they can make some of their own proteins. Mitochondria are the sites of aerobic respiration, where ATP is produced, which is why they are called the powerhouse of the cell.

Lipases split fats into fatty acids and glycerol. Fat digestion happens mainly in the small intestine.

120 mmHg is the systolic pressure when the ventricles contract, and 80 mmHg is the diastolic pressure when they relax.