General Science Mixed Quiz: Set 189

Stretching the wire to twice its length makes its resistance four times larger, so at the same voltage the current falls to a quarter.

Thiamin (thiamine) is vitamin B1, a water-soluble vitamin that helps the body turn carbohydrates into energy and keeps the nerves and heart working well.

Sugar is actively loaded into the sieve tubes at the source, water follows from the xylem by osmosis and raises the pressure there, and the resulting gradient pushes the whole solution to the sink, where sugar is unloaded and water returns to the xylem.

James Watson and Francis Crick published the double helix model in 1953, with two strands running in opposite directions and bases paired on the inside, using the X-ray diffraction photographs produced by Rosalind Franklin and Maurice Wilkins; Watson, Crick and Wilkins shared the Nobel Prize in 1962.

When the block is released suddenly it falls freely at first, so at the lowest point its speed is zero and all the gravitational potential energy it has lost has gone into the spring.

An atomic clock keeps time by locking onto the fixed frequency of radiation that makes atoms such as cesium-133 or rubidium jump between two energy levels.

Farmyard manure is the decomposed mixture of cattle dung, urine and bedding litter, and in general it carries only about half a per cent of nitrogen, along with roughly the same order of phosphate and potash.

Pascal's law says that pressure applied to an enclosed fluid is transmitted undiminished to every part of the fluid and to the walls of the vessel, so a modest push on the brake pedal creates a pressure in the brake fluid that is passed to the wider pistons at every…

The centre of gravity is a geometrical point through which the resultant weight of a body acts, and by symmetry that point for a uniform ring is its geometrical centre, which lies in the empty space inside the ring.

Pitchblende, or uraninite, is the chief ore of uranium, the fuel used in most nuclear power stations. Pitchblende is a heavy, black mineral made mostly of uranium oxide.

In a metal, the outer electrons of the atoms are not tied to any one atom and drift through the lattice when a voltage is applied, carrying the current.

Aluminium has three valence electrons, one fewer than silicon, so each aluminium atom leaves a hole that acts as a positive charge carrier.

Glycolysis spends two molecules of ATP in the preparatory steps that phosphorylate glucose and fructose, and produces four by substrate level phosphorylation in the later steps, so the net gain is two ATP along with two molecules of reduced NAD.

It is the lowest temperature to which a combustible substance must be heated before it begins to burn, and it is a fixed property of that substance; substances with a very low ignition temperature, such as petrol, alcohol and liquefied petroleum gas, are called inflammable substances and are stored with…

The two strips are joined and carry the load together, so they suffer the same strain. Since stress equals the modulus multiplied by the strain, the stress in steel is three times the stress in aluminium.

Carbon fibre is widely used in cars and aircraft for its strength and low weight, and it can be recovered and recycled.

About two or three per cent of gypsum, which is calcium sulphate dihydrate, is ground with the clinker because it slows down the hydration of tricalcium aluminate, the compound that would otherwise set almost the moment water was added and leave no time to place the concrete.

The magnitude of torque is r into F into the sine of the angle between the arm and the force, and the sine of an angle is largest, equal to one, at 90 degrees, so the whole of the force is then used in turning the body.

For a straight wire, the right-hand thumb rule links the current to the circular field lines around it. Hold the wire in the right hand with the thumb along the current; the curled fingers then show the direction of the magnetic field lines, which form concentric circles around the wire.

Breaking stress is the greatest force per unit area that a substance can bear before it snaps, and since both the force and the area are already accounted for in the definition, what remains is a constant of the substance itself, the same for a thin wire and a thick…