General Science GK Questions with Answers – Page 3

The rod becomes negative because it gains electrons from the wool. When two materials are rubbed together, only electrons move, because they are the loosely held outer particles of atoms.

This is the Clausius statement of the second law. Rudolf Clausius stated that heat cannot by itself pass from a colder body to a hotter one; work must be done to make it do so.

Bats send out ultrasonic squeaks and listen for the echoes to locate obstacles and prey. This method is called echolocation.

A rainbow forms when raindrops split white sunlight into its seven colours. When sunlight enters a raindrop, it is refracted, and because each colour bends by a different amount, the colours spread apart.

Washing soda is the crystalline form of sodium carbonate, Na2CO3·10H2O, sodium carbonate decahydrate. Sodium carbonate is made from common salt by the Solvay (ammonia-soda) process.

A mature mammalian red blood cell has no nucleus, ribosomes or mitochondria, so it can neither make proteins nor divide.

Lysosomes are small membrane-bound sacs filled with digestive enzymes, which is why they are called the storehouse of digestive enzymes.

In a thunderstorm we see the lightning first and hear the thunder later, although both are produced at the same moment.

Collagen is the main structural protein of cartilage, and it is a fibrous protein, not a globin. Globins are compact, folded proteins that hold a haem group and carry or store oxygen.

Proteins are made on ribosomes, and the smooth endoplasmic reticulum has no ribosomes on its surface. The endoplasmic reticulum is a network of membrane tubes and sacs in the cytoplasm.

An angle of incidence of 0° means the ray falls along the normal, and a ray along the normal passes into the next medium without bending.

On the pH scale every value below 7 means the solution has more hydrogen ions than hydroxide ions, which is what makes it acidic.

Mitosis keeps the chromosome number unchanged, so it never makes cells haploid; that is the work of meiosis. In mitosis one parent cell divides once and gives two daughter cells that are genetically identical to it.

It is caused by the bacterium Vibrio cholerae, which spreads through food and water polluted with human faeces. The bacterium was identified by Robert Koch in 1883.

Hair turns grey because the chemical make-up of the hair changes as the body stops producing the pigment melanin, so new substances form and the change cannot be reversed.

Lysosomes are small membrane-bound sacs full of hydrolytic enzymes that digest worn-out parts and foreign material inside the cell. Lysosomes are formed from the Golgi apparatus and were discovered by Christian de Duve.

The resistance of a conductor depends on its material and shape, not on how much current flows through it. For a cylindrical conductor, R = ρL/A, where ρ is the resistivity of the material, L the length and A the area of cross-section.

Oxygen makes up about 21 per cent of dry air by volume, second only to nitrogen. Dry air near the ground is about 78 per cent nitrogen, 21 per cent oxygen and 0.93 per cent argon, which is the third most abundant gas.

The enzyme breaks the β-lactam ring that gives penicillin its power. Penicillin was discovered by Alexander Fleming in 1928 from the mould Penicillium notatum.

In an insulator the electrons are tightly bound to their atoms, so there are almost no free electrons to carry a current.