2.5 General Science: Physics, Chemistry & Biology Fundamentals

What This Section Is For

The official Syllabus for Paper-I (Common for all 09 disciplines) opens with General Science — Invention & Discoveries. It is important to understand the register: these are one-line recall items, not the derivation-heavy physics of Paper-II. A Mechanical candidate who can derive the Rankine cycle may still lose easy marks by never revising which vitamin deficiency causes rickets.

Because Paper-I carries its own qualifying floor of 40, 35 or 30 marks by category, these cheap marks are not optional.

Physics: Units, Laws and Constants

SI base units

Derived units worth attaching to a name: newton (force), pascal (pressure), joule (energy), watt (power), hertz (frequency), coulomb (charge), volt (potential), ohm (resistance), farad (capacitance), tesla (magnetic flux density), weber (magnetic flux), henry (inductance).

Named laws

Key constants: acceleration due to gravity $\approx 9.81$ m/s$^2$; speed of light $3\times10^{8}$ m/s; speed of sound in air $\approx 343$ m/s at 20 degrees Celsius; standard atmospheric pressure 101.325 kPa or 760 mm of mercury.

Chemistry, With a Coal-Sector Bias

Since this is a Coal India paper, the chemistry most likely to appear is combustion and fuel chemistry.

The coalification series

Carbon content and calorific value rise along the series while moisture and volatile matter fall. Anthracite is the highest rank and burns with a nearly smokeless flame; India's small anthracite deposits are in Jammu and Kashmir.

Mine gases

The Davy safety lamp, invented by Sir Humphry Davy in 1815, enclosed the flame in wire gauze that conducted heat away and prevented ignition of firedamp. It remains the archetypal example of an invention driven directly by coal mining.

Chemistry: Core Recall

• Atomic structure. Protons and neutrons in the nucleus; electrons in shells. Atomic number = protons; mass number = protons + neutrons. Isotopes share atomic number but differ in mass number.
• Periodic table. Devised by Dmitri Mendeleev (1869) on atomic mass; the modern table is ordered by atomic number following Moseley. Groups run vertically, periods horizontally.
• Acids and bases. pH below 7 is acidic, 7 is neutral, above 7 is basic. pH is a logarithmic scale, so a change of one unit is a tenfold change in hydrogen-ion concentration.
• Common chemical names. Common salt is sodium chloride; baking soda is sodium bicarbonate; washing soda is sodium carbonate; quicklime is calcium oxide; slaked lime is calcium hydroxide; plaster of Paris is calcium sulphate hemihydrate; bleaching powder is calcium hypochlorite; caustic soda is sodium hydroxide.
• Alloys. Brass is copper and zinc; bronze is copper and tin; steel is iron and carbon; stainless steel adds chromium and nickel; solder is lead and tin; duralumin is aluminium with copper, magnesium and manganese.
• Gases. The atmosphere is about 78% nitrogen and 21% oxygen. Ozone shields ultraviolet radiation. Carbon dioxide, methane and nitrous oxide are the principal greenhouse gases; methane has a far higher global warming potential than carbon dioxide over a twenty-year horizon, which is why coal-mine methane capture is a policy priority.

Biology: Core Recall

Vitamins and deficiency diseases

Vitamins A, D, E and K are fat-soluble; the B group and C are water-soluble.

Human systems in brief

• The heart has four chambers; normal adult resting pulse is about 72 beats per minute. Blood pressure is quoted as systolic over diastolic, nominally 120 over 80 mm of mercury.
• Blood groups: A, B, AB and O with Rh factor. Group O negative is the universal donor; AB positive is the universal recipient.
• The liver is the largest internal gland; the skin is the largest organ. The pancreas secretes insulin, whose deficiency causes diabetes mellitus.
• Respiration exchanges oxygen for carbon dioxide in the alveoli. The occupational lung disease of coal mining is pneumoconiosis, caused by prolonged inhalation of respirable coal dust, which is why dust suppression and respirable-dust standards feature in mine regulation.
• Photosynthesis converts carbon dioxide and water into glucose using chlorophyll and sunlight, releasing oxygen. It is the ultimate origin of the plant matter that, buried and compressed over geological time, became coal.