General Science Previous Year Questions (PYQ) with Answers – Page 56

Neutrons sit inside the nucleus with protons; it is the electrons that move around the nucleus. The neutron was discovered by James Chadwick in 1932, and he received the Nobel Prize in Physics for it in 1935.

Gravitational force varies inversely with the square of the distance, so doubling the distance cuts the force to one-fourth.

The cervix is the narrow lower neck of the uterus and belongs to the female reproductive system. In the male, sperms are made in the testes, which lie in the scrotum outside the body because sperm formation needs a temperature a little lower than body temperature.

In a short circuit the resistance of the path falls almost to zero, so by Ohm's law the current rises sharply.

This statement is false, because sound in air travels as longitudinal waves, not transverse waves. In a longitudinal wave, the particles of the medium vibrate back and forth along the direction in which the wave moves, forming compressions and rarefactions.

Kinetic energy equals p²/2m, so doubling the momentum p makes the kinetic energy four times as large. Momentum is p = mv and kinetic energy is KE = ½mv².

The eye lens focuses light on the retina, the light-sensitive layer at the back of the eye, where a real and inverted image is formed.

The force exerted by light depends on how much light falls on the surface, so with the same intensity, half the area receives half the light and feels half the force.

Each half of the wire has a resistance of 10 Ω, and two 10 Ω resistors in parallel give 5 Ω. The resistance of a wire is R = ρL/A, so it is directly proportional to its length when the material and thickness stay the same.

The urinary bladder is a hollow muscular sac made of smooth muscle and a stretchable lining; it has no cartilage.

Sclerenchyma cells are dead at maturity, with thick walls hardened by lignin. Sclerenchyma is the tissue that makes plants hard and stiff.

A kilogram-metre per second squared is mass times acceleration, which is force; it is the newton, not a unit of energy.

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.

In many single-celled organisms such as Amoeba and Paramecium, a special contractile vacuole collects excess water and some wastes from the cytoplasm and pumps them out of the cell.

Almost all the mass of an atom is in its nucleus, so the mass number, which the question calls atomic mass, is the total of protons and neutrons, the two kinds of nucleons.

The atomic number, the number of protons in the nucleus, decides which element an atom is, and no two elements share it.

Chloropropane has two carbon–carbon bonds, seven carbon–hydrogen bonds and one carbon–chlorine bond, all single covalent bonds, making 10 in total.

This statement is false, because diamond is an electrical insulator: all four valence electrons of each carbon atom are locked in covalent bonds, leaving no free electrons to carry current.

Magnetic field lines are always closed curves, so the statement that they are open curves is the incorrect one. Outside a magnet, field lines run from the north pole to the south pole; inside the magnet they continue from the south pole back to the north pole, closing the loop.

The refrigerator uses 5 kW × 10 h × 30 days = 1,500 kWh, and at ₹ 4 per kWh that costs ₹ 6,000.