General Science Mixed Quiz: Set 75

Constant velocity means both the speed and the direction stay the same, so the speed cannot change. Velocity is a vector: it has a magnitude, the speed, and a direction.

Accelerators speed up the vulcanisation of rubber; they are not a part of paint.

Radiant heat is infrared electromagnetic radiation, so it travels in straight lines at the speed of light. Heat moves in three ways.

A mole is a count, not a weight: one mole of any element holds 6.022 into 10 to the power 23 atoms, the Avogadro number, whatever the element is.

The heater's resistance is 220/0.5 = 440 Ω, so at 120 V the current is 120/440, about 0.27 A. By Ohm's law, V = IR, and for an ohmic conductor at a steady temperature the resistance stays the same.

The tiny pores on the surface of a leaf, found mostly on its lower side, are called stomata. Each stoma is a slit guarded by two bean shaped guard cells, which swell to open it and shrink to close it.

These are the three places in a eukaryotic cell where DNA is found. The nucleus holds nearly all of a cell's DNA, packed with proteins into chromosomes.

Hooke's law holds only as far as the limit of proportionality, and that limit is either equal to or lower than the elastic limit, so statements 1 and 4 are the correct pair.

Bile has no digestive enzymes at all; it only prepares fats for digestion by other enzymes. Bile is made by the liver, stored and concentrated in the gall bladder, and poured into the duodenum through the bile duct.

Time period is the time taken for one full oscillation, so it is the total time divided by the number of oscillations: 64 divided by 40 gives 1.6 seconds.

A magnesium atom sits at the centre of every chlorophyll molecule, so a plant cannot make chlorophyll without it. Chlorophyll is built around a ring-shaped structure called a porphyrin, with a single magnesium ion held at its centre.

Anabaena is a cyanobacterium, a prokaryote with no true nucleus, and all prokaryotes are placed in Monera. In R.H.

Transcription is the step in which the genetic message of a gene is copied from one strand of DNA into a strand of RNA.

Hydra, starfish and planaria can all grow a lost or cut off part of the body back into a whole animal, and that ability is called regeneration.

The melting point is the minimum temperature at which a solid melts to become a liquid at atmospheric pressure, not the maximum.

A bacterium is a living cell filled with cytoplasm, while a virus is only genetic material inside a protein coat.

Power is the reciprocal of focal length in metres, and a concave lens has a negative focal length. The power of a lens is P = 1/f, with f in metres, and its unit is the dioptre (D).

An LED is a p-n junction diode that gives out light when current flows through it in the forward direction.

Nichrome has a high resistivity and does not oxidise easily when red hot, so it is the standard heating element.

Wendell Meredith Stanley crystallised the tobacco mosaic virus and showed that the crystals were made chiefly of protein, work that proved a virus could be handled like a chemical substance and won him a share of a Nobel Prize.