General Science is a big part of SSC and RRB papers, and static science facts also appear in bank exam GA sections. This page covers the four most repeated areas: instruments, units, inventions and Indian scientists.
Scientific instruments and their uses
| Instrument | Measures / used for |
|---|---|
| Altimeter | Altitude (height) of an aircraft |
| Ammeter | Electric current |
| Anemometer | Wind speed |
| Audiometer | Hearing ability |
| Barometer | Atmospheric pressure |
| Bolometer | Heat radiation |
| Calorimeter | Quantity of heat |
| Cardiograph (ECG) | Heart’s electrical activity |
| Chronometer | Accurate time at sea (longitude) |
| Dynamo | Converts mechanical energy into electrical energy |
| Electroencephalograph (EEG) | Brain’s electrical activity |
| Fathometer | Depth of the sea |
| Galvanometer | Detects small electric currents |
| Geiger counter | Radioactivity |
| Hydrometer | Relative density (specific gravity) of liquids |
| Hygrometer | Humidity of air |
| Lactometer | Purity (density) of milk |
| Manometer | Pressure of gases |
| Odometer | Distance travelled by a vehicle |
| Ohmmeter | Electrical resistance |
| Periscope | Seeing objects above water from a submarine |
| Photometer | Light intensity |
| Pyrometer | Very high temperatures |
| Rain gauge (pluviometer) | Rainfall |
| Seismograph | Earthquake waves |
| Sextant | Angle between a star/sun and the horizon (navigation) |
| Speedometer | Speed of a vehicle |
| Sphygmomanometer | Blood pressure |
| Stethoscope | Heart and lung sounds (invented by René Laennec, 1816) |
| Tachometer | Speed of rotation (RPM) |
| Thermostat | Keeps temperature constant |
| Voltmeter | Potential difference (voltage) |
| Crescograph | Growth of plants (invented by J.C. Bose) |
SI units
The 7 base units
| Quantity | Unit | Symbol |
|---|---|---|
| Length | metre | m |
| Mass | kilogram | kg |
| Time | second | s |
| Electric current | ampere | A |
| Temperature | kelvin | K |
| Amount of substance | mole | mol |
| Luminous intensity | candela | cd |
Since 20 May 2019, all 7 base units are defined using fixed natural constants (the kilogram now uses Planck’s constant).
Important derived units
| Quantity | Unit | Quantity | Unit |
|---|---|---|---|
| Force | newton (N) | Electric charge | coulomb (C) |
| Work / energy | joule (J) | Potential difference | volt (V) |
| Power | watt (W) | Resistance | ohm (Ω) |
| Pressure | pascal (Pa) | Capacitance | farad (F) |
| Frequency | hertz (Hz) | Magnetic flux density | tesla (T) |
| Illuminance | lux | Magnetic flux | weber (Wb) |
| Radioactivity | becquerel (Bq) | Inductance | henry (H) |
Other units to remember: light year (distance), parsec (distance; about 3.26 light years), angstrom (10⁻¹⁰ m, wavelength), knot (speed at sea), nautical mile (1.852 km), decibel (sound level), horsepower (about 746 watts), carat (purity of gold / mass of gems).
Inventions and inventors
| Invention | Inventor | Year |
|---|---|---|
| Telephone | Alexander Graham Bell | 1876 |
| Electric bulb (practical) | Thomas Edison | 1879 |
| Radio (wireless telegraphy) | Guglielmo Marconi | 1895 |
| Television | John Logie Baird | 1926 |
| Aeroplane | Wright brothers | 1903 |
| Steam engine (improved) | James Watt | 1769 |
| Dynamite | Alfred Nobel | 1867 |
| Printing press | Johannes Gutenberg | c. 1440 |
| Analytical engine (computer) | Charles Babbage | 1830s |
| World Wide Web | Tim Berners-Lee | 1989 |
| Telescope (astronomical use) | Galileo Galilei | 1609 |
| Diesel engine | Rudolf Diesel | 1892 |
| Safety lamp | Humphry Davy | 1815 |
Discoveries
| Discovery | Scientist | Year |
|---|---|---|
| Cell | Robert Hooke | 1665 |
| Laws of motion, gravitation | Isaac Newton | 1687 |
| Smallpox vaccine | Edward Jenner | 1796 |
| Periodic table | Dmitri Mendeleev | 1869 |
| Rabies vaccine | Louis Pasteur | 1885 |
| X-rays | Wilhelm Röntgen | 1895 |
| Radioactivity | Henri Becquerel | 1896 |
| Electron | J.J. Thomson | 1897 |
| Blood groups | Karl Landsteiner | 1901 |
| Theory of relativity | Albert Einstein | 1905 (special) |
| Atomic nucleus | Ernest Rutherford | 1911 |
| Insulin | Banting and Best | 1921 |
| Penicillin | Alexander Fleming | 1928 |
| Neutron | James Chadwick | 1932 |
| Polio vaccine (injectable) | Jonas Salk | 1955 |
| DNA double helix | Watson and Crick | 1953 |
Indian scientists and their contributions
| Scientist | Known for |
|---|---|
| C.V. Raman | Raman Effect (1928); Nobel Prize in Physics (1930) |
| J.C. Bose | Crescograph; plants respond to stimuli; radio waves research |
| S.N. Bose | Bose–Einstein statistics; “boson” named after him |
| Meghnad Saha | Saha ionisation equation (astrophysics) |
| Homi J. Bhabha | Father of India’s nuclear programme |
| Vikram Sarabhai | Father of India’s space programme |
| Srinivasa Ramanujan | Number theory; 1729 (Hardy–Ramanujan number) |
| S. Chandrasekhar | Chandrasekhar limit (stars); Nobel in Physics (1983) |
| Har Gobind Khorana | Genetic code; Nobel in Medicine (1968) |
| Venkatraman Ramakrishnan | Ribosome structure; Nobel in Chemistry (2009) |
| A.P.J. Abdul Kalam | “Missile Man of India”; led SLV-3 and IGMDP |
| M.S. Swaminathan | Father of the Green Revolution in India |
| Verghese Kurien | Father of the White Revolution (Operation Flood) |
| Satish Dhawan | Led ISRO; Sriharikota launch centre named after him |
| Prafulla Chandra Ray | Father of Indian chemistry; founded Bengal Chemicals |
Exam-ready one-liners
- Hygrometer: humidity; hydrometer: density of liquids; lactometer: purity of milk.
- Sphygmomanometer measures blood pressure; seismograph records earthquakes.
- Fathometer measures sea depth; altimeter measures altitude.
- The 7 SI base units include the ampere, kelvin, mole and candela.
- Pascal is the unit of pressure; tesla is the unit of magnetic flux density.
- Penicillin: Alexander Fleming (1928); X-rays: Röntgen (1895).
- Crescograph was invented by J.C. Bose.
- Homi Bhabha: nuclear programme; Vikram Sarabhai: space programme.
Related reading
Quiz: test yourself
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Dates of inventions are as commonly cited in exam books; some differ slightly by source.
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