UPSC NDA & NA General Science (GAT - Part B) Syllabus

Define the audible frequency range for humans and the terms infrasonic and ultrasonic.

Humans hear 20 Hz to 20,000 Hz. Infrasonic is below 20 Hz; ultrasonic is above 20,000 Hz.

What is an echo, and what causes it?

An echo is the repetition of a sound caused by reflection of sound waves from a distant surface, heard distinctly when the reflected sound returns after at least 0.1 second.

Give the equation relating the speed, frequency, and wavelength of a wave.

v = f x lambda, where v = speed, f = frequency, and lambda = wavelength.

What is the approximate speed of light in vacuum, and is light a transverse or longitudinal wave?

About 3 x 10^8 m/s (299,792,458 m/s). Light is a transverse electromagnetic wave.

State the laws of reflection of light.

1) The angle of incidence equals the angle of reflection. 2) The incident ray, reflected ray, and normal at the point of incidence all lie in the same plane.

What is refraction of light, and what is dispersion?

Refraction is the bending of light as it passes between media of different optical densities. Dispersion is the splitting of white light into its constituent colours (VIBGYOR) by a prism.

List the seven colours of the visible spectrum (VIBGYOR) in order of increasing wavelength.

Violet, Indigo, Blue, Green, Yellow, Orange, Red (red has the longest wavelength, violet the shortest).

State Ohm's law and its formula.

At constant temperature, the current through a conductor is directly proportional to the voltage across it: V = IR, where V = voltage, I = current, R = resistance.

What is the SI unit of electric current, charge, and resistance?

Current: ampere (A); charge: coulomb (C); resistance: ohm (Omega).

Give the formula for electric power in terms of voltage and current.

P = VI (also P = I^2 R = V^2/R), where P is power in watts.

Distinguish between a series and a parallel circuit regarding resistance.

In series, resistances add (R = R1 + R2 + ...) and current is the same throughout. In parallel, 1/R = 1/R1 + 1/R2 + ... (total resistance decreases) and voltage is the same across each branch.

What is the difference between a conductor, an insulator, and a semiconductor?

A conductor allows electricity to flow easily (e.g. copper); an insulator resists flow (e.g. rubber); a semiconductor has intermediate conductivity that can be controlled (e.g. silicon).

State the rule for like and unlike magnetic poles, and name the magnetic material par excellence.

Like poles repel and unlike poles attract. Iron is the classic ferromagnetic material (others: cobalt, nickel).

What is electromagnetic induction (Faraday's law)?

A changing magnetic flux through a circuit induces an electromotive force (emf); the magnitude of induced emf is proportional to the rate of change of magnetic flux. It is the working principle of generators.

Name the six simple machines.

Lever, pulley, wheel and axle, inclined plane, wedge, and screw.

Define mechanical advantage of a machine.

Mechanical advantage (MA) is the ratio of load (output force) to effort (input force): MA = Load/Effort. It tells how much a machine multiplies force.

What are the three classes of levers, distinguished by the position of the fulcrum, load, and effort?

Class 1: fulcrum between load and effort (e.g. seesaw). Class 2: load between fulcrum and effort (e.g. wheelbarrow). Class 3: effort between fulcrum and load (e.g. tweezers/forearm).

What everyday device converts electrical energy into mechanical energy, and which converts mechanical into electrical?

An electric motor converts electrical energy to mechanical energy; a generator (dynamo) converts mechanical energy to electrical energy.

Distinguish between an element, a compound, and a mixture.

An element is made of one kind of atom (e.g. oxygen). A compound is two or more elements chemically combined in fixed ratio (e.g. water). A mixture contains substances physically combined in any ratio, separable by physical means.

What is the difference between a physical change and a chemical change?

A physical change alters form or state without forming a new substance and is usually reversible (e.g. melting ice). A chemical change forms a new substance with new properties and is usually irreversible (e.g. burning).

Name and describe the three subatomic particles of an atom with their charges.

Proton (positive charge, in nucleus), neutron (no charge, in nucleus), and electron (negative charge, orbiting the nucleus).

Define atomic number and mass number.

Atomic number (Z) is the number of protons in an atom's nucleus. Mass number (A) is the total number of protons plus neutrons.

What are isotopes?

Isotopes are atoms of the same element having the same atomic number (same protons) but different mass numbers (different numbers of neutrons), e.g. C-12 and C-14.

Distinguish between ionic and covalent bonds.

An ionic bond forms by transfer of electrons between atoms, creating charged ions (e.g. NaCl). A covalent bond forms by sharing of electron pairs between atoms (e.g. H2O).

Define acids and bases in terms of pH and ion production.

Acids release H+ ions in water and have pH below 7; bases (alkalis) release OH- ions and have pH above 7. A neutral solution has pH 7.

What is oxidation and what is reduction (in terms of electrons)?

Oxidation is the loss of electrons (or gain of oxygen/loss of hydrogen); reduction is the gain of electrons (or loss of oxygen/gain of hydrogen). They occur together in redox reactions.

Name the common chemical name and formula for: (a) common salt, (b) baking soda, (c) quicklime.

(a) Common salt = sodium chloride, NaCl. (b) Baking soda = sodium bicarbonate, NaHCO3. (c) Quicklime = calcium oxide, CaO.

What is an alloy, and give the composition of brass and bronze.

An alloy is a homogeneous mixture of two or more metals (or metal and non-metal). Brass = copper + zinc; Bronze = copper + tin.

What is the basic structural and functional unit of all living organisms, and who discovered it?

The cell is the basic structural and functional unit of life; Robert Hooke discovered cells (in cork) in 1665.

Distinguish between prokaryotic and eukaryotic cells, and name the powerhouse of the cell.

Prokaryotic cells lack a true nucleus and membrane-bound organelles (e.g. bacteria); eukaryotic cells have a true nucleus and membrane-bound organelles (e.g. plant/animal cells). The mitochondrion is the powerhouse of the cell.

Name the parts of the human digestive system in order and the main organ of respiratory gas exchange.

Digestive path: mouth, oesophagus, stomach, small intestine, large intestine, rectum, anus. The lungs (via the alveoli) are the site of gas exchange in the respiratory system.