General Science Mixed Quiz: Set 168

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.

Entomology is the branch of zoology that deals with insects, the largest class of animals, and it covers their structure, classification, life cycles and their role as pests and pollinators.

That is false: in a physical change the molecules stay the same, and only their arrangement, state or shape alters.

In this cell hydrogen is fed to the anode and oxidised, oxygen is fed to the cathode and reduced, and the two combine to give water, so the cell produces electricity for as long as the gases are supplied and leaves no polluting exhaust.

A photographer's flash tube is filled with xenon, which gives an intense burst of white light when a high-voltage spark passes through it.

Crown gall is caused by the bacterium Agrobacterium tumefaciens, which enters through a wound near the base, or crown, of the stem and makes the plant grow rough tumour-like swellings there.

The human eye responds only to visible light, which lies roughly between 400 nm (violet) and 700 nm (red), and 500 nm is the only one of the three values in that range.

When light of a suitable frequency falls on a metal and knocks electrons out of it, the process is called photoelectric emission.

By Charles's law the volume of a fixed mass of gas at constant pressure is proportional to its absolute temperature, so heating the air inside the envelope makes it expand; some of it escapes from the open mouth, the mass of air left inside falls, its density becomes lower than…

One mole of any gas occupies 22.4 litres at STP, so 5.6 litres is 5.6 divided by 22.4, that is one quarter of a mole.

The epidemic of the 1840s destroyed the potato crop of Ireland and brought on the famine, and the study of that outbreak by Anton de Bary established plant pathology as a science.

In facilitated transport, molecules cross the membrane with the help of membrane proteins, while still moving down their concentration gradient.

The equivalent weight of a base is its molecular weight divided by its acidity, which is the number of replaceable hydroxide ions in one molecule.

Clay is a plastic material: it deforms permanently under even a small force, so its stress is not proportional to its strain.

A hypertonic solution has a higher solute concentration than the cell sap, so water leaves the cells by osmosis and the protoplast shrinks away from the cell wall.

Treating rock phosphate, which is insoluble calcium phosphate, with sulphuric acid gives superphosphate of lime, a fertiliser whose phosphorus plants can absorb.

There is no compound with the formula 4CaO·SiO₂ in Portland cement; the four main compounds of cement clinker are dicalcium silicate, tricalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite.

A freely pivoted magnetic needle turns to line up with any magnetic field around it, so its deflection shows that a field is present and which way it points.

Genuine currency notes carry security features printed with fluorescent inks that glow only under ultraviolet light, so a UV lamp quickly exposes a fake.

Extending the straight line of Charles's law backwards shows that the volume of an ideal gas would become zero at minus 273.15 degrees Celsius, and this point is taken as the zero of the kelvin or absolute scale, at which molecular motion carries its least possible energy.