General Science for the Assam Police Constable (AB & UB) Exam
General Science is the steadiest scorer inside the General Knowledge block of the SLPRB Assam Police Constable paper. The questions are taken from Physics, Chemistry and Biology at the level taught in classes six to ten, and they almost always turn on a single fact: a unit, a symbol, the work of an organ, the name of a disease, or the scientist linked with a discovery. This page gathers those single facts and arranges them subject by subject, so that revision becomes a matter of reading a short list rather than studying a long chapter. The material follows the NCERT school science textbooks and the standard reference matter used for the Assam recruitment examinations, and it is reviewed before publication. The purpose is not to make the candidate a scientist but to make sure that no easy science question is ever left blank.
How the General Science Portion Is Set
The paper does not ask for derivations or long explanations. It asks for recognition. A candidate is shown four names and asked which one discovered a particular thing, or four units and asked which one measures a particular quantity, or four organs and asked which one does a particular job. Because the same small set of facts is recycled year after year, the subject is best handled by memorising the high-yield table given below and then testing it against previous papers.
Physics: Motion, Force and Energy
Physics questions in this paper are mostly about units and laws. The three laws of motion were given by Isaac Newton; the first is the law of inertia, the second states that force equals mass times acceleration, and the third states that every action has an equal and opposite reaction. The acceleration due to gravity near the earth's surface is about 9.8 metres per second squared, and the speed of light in vacuum is about three hundred thousand kilometres per second. Sound travels faster in solids than in liquids and faster in liquids than in gases, and it cannot travel through a vacuum. Work is force multiplied by distance, and power is work divided by time. Energy exists in many forms and is measured in joules.
Units and Measurements Worth Remembering
- Length: metre; mass: kilogram; time: second; temperature: kelvin.
- Force: newton; pressure: pascal; energy and work: joule; power: watt.
- Frequency: hertz; electric current: ampere; potential difference: volt; resistance: ohm.
- The instrument to measure atmospheric pressure is the barometer; blood pressure is measured with a sphygmomanometer; temperature with a thermometer.
Light, Heat and Electricity
Light bends when it passes from one medium to another, and this bending is called refraction; the bouncing back of light from a surface is called reflection. A convex lens converges light and is used to correct long sight, while a concave lens diverges light and is used to correct short sight. Heat travels by conduction in solids, by convection in liquids and gases, and by radiation without any medium. In electricity, Ohm's law states that the current through a conductor is proportional to the potential difference across it, and the relation is written as voltage equals current times resistance. A fuse wire is made of a metal with a low melting point so that it melts and breaks the circuit when the current becomes too large.
Chemistry: Atoms, Elements and Formulae
An atom has a nucleus of protons and neutrons, with electrons moving around it. The number of protons is the atomic number of the element. The periodic table was first arranged in a systematic form by Dmitri Mendeleev. The chemical formula of water is H2O, of common salt is NaCl, of carbon dioxide is CO2, of ammonia is NH3, and of sulphuric acid is H2SO4. Oxygen supports combustion, hydrogen is the lightest gas, and nitrogen forms about seventy-eight per cent of the air we breathe.
Acids, Bases and Common Chemical Names
An acid turns blue litmus paper red, a base turns red litmus paper blue, and the strength of an acid or a base is measured on the pH scale, where a value of seven is neutral. Many substances have a common name and a chemical name, and the examination likes to ask for the pair.
- Baking soda: sodium bicarbonate, NaHCO3.
- Washing soda: sodium carbonate, Na2CO3.
- Quick lime: calcium oxide, CaO; slaked lime: calcium hydroxide, Ca(OH)2.
- Marble and chalk: calcium carbonate, CaCO3.
- Plaster of Paris: calcium sulphate hemihydrate; bleaching powder: calcium oxychloride.
- Table salt: sodium chloride, NaCl.
Biology: The Human Body and Health
Biology carries the largest number of easy questions. The adult human body has 206 bones, the longest of which is the femur and the smallest the stapes in the ear. The heart has four chambers, the liver is the largest gland, and the lungs are the organs of respiration. Blood is made up of red blood cells, white blood cells, platelets and plasma, and the normal blood pressure of a healthy adult is about 120 over 80 millimetres of mercury. The nervous system is controlled by the brain, and the spinal cord carries messages to and from it.
Vitamins, Diseases and Discoveries
- Deficiency of vitamin A causes night blindness; of vitamin C, scurvy; of vitamin D, rickets; and of vitamin K, poor clotting of blood.
- Malaria is caused by the Plasmodium parasite and is spread by the female Anopheles mosquito; dengue is spread by the Aedes mosquito.
- Tuberculosis is caused by a bacterium; polio is caused by a virus; the BCG vaccine is given against tuberculosis.
- Sir Alexander Fleming discovered penicillin; Edward Jenner worked on the smallpox vaccine; Ronald Ross worked on malaria; Louis Pasteur gave pasteurisation.
- Sir C. V. Raman discovered the Raman effect; Homi J. Bhabha is remembered as the father of the Indian nuclear programme.
Plants and the Environment
Green plants make their own food by photosynthesis, in which carbon dioxide and water are converted into carbohydrate in the presence of sunlight and chlorophyll, and oxygen is released. Green plants are therefore called producers in a food chain. The ozone layer in the upper atmosphere protects living beings from harmful ultraviolet rays, while gases such as carbon dioxide and methane are called greenhouse gases because they trap heat and contribute to global warming.
Common Traps in This Block
- Mixing up the second and third laws of motion.
- Writing the unit of force as joule instead of newton.
- Confusing the melting point of a fuse wire with its boiling point.
- Mixing the transmission of malaria with that of dengue.
- Confusing the deficiency disease of vitamin A with that of vitamin C.
A Revision Plan for This Block
- Make one page of units and quantities and revise it first thing every week.
- Learn the common-name and chemical-name pairs in a single column.
- Make a table of diseases with their cause and their carrier.
- Learn the inventors and discoverers with a single keyword each.
- Solve the science questions of at least five previous papers to see how the facts are worded.
Frequently Asked Questions
Which gas is most abundant in the earth's atmosphere?
Nitrogen, which forms about seventy-eight per cent of the air. Oxygen, the gas that supports combustion and breathing, forms about twenty-one per cent.
What is the chemical formula of common salt?
The chemical formula of common salt is NaCl, sodium chloride. It is an ionic compound formed from sodium and chlorine.
How many bones are there in the adult human body?
There are 206 bones in the adult human body. At birth a baby has more bones, and many of them fuse as the body grows.
Who discovered the law of gravitation?
Isaac Newton is credited with the law of universal gravitation. He also gave the three laws of motion on which classical mechanics rests.
What instrument is used to measure blood pressure?
Blood pressure is measured with a sphygmomanometer. Atmospheric pressure is measured with a barometer, which is a different instrument.