General Science Previous Year Questions (PYQ) with Answers – Page 69

When cells are joined in parallel all their positive terminals are connected together and all their negative terminals together, so each cell is across the same two points and the voltage of the combination is the voltage of one cell, that is 12 volts.

The working rule for charging a storage battery is that the charging current should be about one-tenth of the ampere-hour capacity of the battery, which is called the C by 10 rate.

Aluminium is the most abundant metal in the crust of the earth, making up about eight per cent of it by weight.

Archimedes used his principle to test whether the crown of King Hiero II of Syracuse was pure gold. The principle says that a body immersed in a fluid is buoyed up by a force equal to the weight of the fluid it displaces.

Gravitational force is directly proportional to each mass, so doubling one mass doubles the force. Newton law of universal gravitation states that the force between two bodies is F equal to G m1 m2 divided by r squared.

Calorific value is the heat released on completely burning one gram of a substance, and among the four foods listed ghee has the highest, because it is almost entirely fat.

A hydrogen bomb, also called a thermonuclear bomb, works in two steps. A fission explosion of uranium or plutonium produces the temperature of millions of degrees needed to force light nuclei together, and the fusion of those nuclei then releases far more energy than the fission stage alone.

Myopia, or short-sightedness, is the defect in which nearby objects are seen clearly but distant objects look blurred. It arises either because the eye lens has become too converging, that is its focal length is too short, or because the eyeball has grown too long from front to back.

In a capillary tube the height of rise is directly proportional to the surface tension of the liquid and inversely proportional to its density and the radius of the tube.

The upthrust on a body is the resultant of the pressure forces of the fluid around it, and that resultant acts through the centre of gravity of the fluid the body has pushed aside, which is why the point is called the centre of buoyancy.

A floating body displaces its own weight of fluid, so the fraction of its volume that lies below the surface equals the ratio of its density to the density of the fluid, here 920 divided by 1000, which is 0.92.

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.

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.

Coulomb friction, also called dry friction, is the resistance that acts when two solid surfaces touch each other with no lubricant between them.

In electroplating the article to be coated is made the cathode, the plating metal serves as the anode, and both are dipped in an electrolyte containing a salt of that metal.

Balance is controlled by the inner ear, which holds the vestibular apparatus alongside the organ of hearing. It is made of three semicircular canals set at right angles to one another and two small sacs, the utricle and the saccule.

The speed of any wave is its frequency multiplied by its wavelength, so here 200 Hz times 2 m gives 400 metres per second.

A concave lens, also called a diverging lens, spreads out the rays that fall on it and so can never bring them to a real focus.

Wetting is decided by a contest between two forces: cohesion, the attraction among the molecules of the liquid itself, and adhesion, the attraction between the liquid and the solid surface.

The atomic number of an element is by definition the number of protons in its nucleus, so an atomic number of 11 means 11 protons.