General Science GK Questions with Answers – Page 15

The mass of one mole of any substance, expressed in grams, is by definition its molar mass. One mole contains the Avogadro number of particles, about 6.022 × 10 23, so the molar mass links the mass we can weigh to the number of atoms or molecules present.

A fuse must carry the normal current, so it must conduct, and it must melt quickly when the current becomes too large.

Tungsten is used for the filament because it has the highest melting point of all metals, about 3,422°C, and can glow white-hot without melting.

The average atomic mass is the weighted mean of the isotope masses, taking each in proportion to how common it is.

The friction between the blocks is the only force that drags the top block along, and its largest possible value is μ times the normal force from the top block.

A compound microscope uses two converging lenses, the objective and the eyepiece, to give a greatly magnified image of a tiny object.

The two ends of a diameter split the ring into two equal halves of 10 Ω each, and these two halves are connected in parallel.

The field at the centre of a coil is proportional to the number of turns and inversely proportional to the radius, so doubling N and halving R makes it four times larger.

LIGO uses laser beams in long perpendicular arms to detect the tiny stretching of space caused by gravitational waves. LIGO has two detectors in the United States, at Hanford in Washington and Livingston in Louisiana, each with arms 4 km long.

Rutherford's gold foil experiment of 1911 showed that an atom's positive charge and almost all its mass sit in a tiny central nucleus.

Power is the work done divided by the time taken, and here the work is the potential energy gained by the mass.

A sphygmomanometer has an inflatable cuff wrapped around the upper arm, a rubber bulb to pump air into it, and a gauge, traditionally a column of mercury.

When an electric current is passed through brine, a concentrated aqueous solution of sodium chloride, the salt decomposes. Chlorine gas is given off at the anode and hydrogen gas at the cathode, while sodium hydroxide is left in the solution near the cathode.

RNA is usually single-stranded and its sugar, ribose, carries an extra hydroxyl group, which makes the molecule more reactive and easier to break or alter than double-stranded DNA.

By Newton's law of gravitation, the acceleration due to gravity at the surface is g = GM/R², where G is the universal gravitational constant, M is the mass of the Earth and R is its radius.

Molarity and molality are both standard ways of stating how much solute is present in a solution.

Torque is r into F into the sine of the angle between them, and since the force here is perpendicular to the rod the sine is one, so the torque is simply 0.5 multiplied by 20, that is 10 newton metre.

Varignon theorem states that the moment of a force about any point equals the algebraic sum of the moments of its components about the same point; it speaks of the moments themselves, not of their squares, so statement S1 is false as written.

Moment of inertia is the sum of each bit of mass multiplied by the square of its distance from the axis, so drawing the arms in reduces it.

A solid cone has more material near its wide base than near its apex, so its centre of gravity lies on the axis of symmetry well below the middle, at one quarter of the height measured from the base, which is three quarters of the height measured down from the…