Class 12th Element of Science Most Expected Questions With answers NCERT || Half Yearly Exam 2026-27 MP Board Elements of Science Most Important Questions answer English Medium
Section A: Agriculture Physics
Q1. State Archimedes' Principle. How is relative density determined using a hydrometer?
Archimedes’ principle states that a body immersed in a fluid experiences an upward buoyant force equal to the weight of the displaced fluid. A hydrometer floats in the liquid, and its sinking depth depends on liquid density. The calibrated stem directly gives relative density, useful in milk and soil-solution tests.
Q2. Explain atmospheric pressure. Describe the construction and working of a Fortin's barometer.
Atmospheric pressure is the force exerted by air per unit area. A Fortin’s barometer has a glass tube filled with mercury, inverted in a mercury reservoir. The mercury column height balances atmospheric pressure. The ivory pointer and vernier scale help read the mercury level accurately.
Q3. Differentiate between force pump and vacuum pump with suitable diagrams.
A force pump lifts water by pressure and can raise water to greater heights; it has a piston and valves. A vacuum pump removes air to create partial vacuum and lifts water by atmospheric pressure. Force pumps are used for irrigation; vacuum pumps are used in laboratories and suction systems.
Q4. State the laws of friction. What are the advantages and disadvantages of friction in agriculture?
Friction opposes relative motion. Its laws state that friction is proportional to normal reaction, depends on surfaces, and is independent of area. In agriculture, friction helps wheel grip, threshing, and belt drives, but causes wear, heat, and extra power loss in machines.
Q5. Define mechanical advantage, velocity ratio, and efficiency of a simple machine.
Mechanical advantage is load divided by effort. Velocity ratio is distance moved by effort divided by distance moved by load. Efficiency is useful work output divided by work input, expressed as percentage. Efficiency equals mechanical advantage divided by velocity ratio multiplied by 100.
Q6. Derive the relation between 'G' (universal gravitational constant) and 'g' (acceleration due to gravity).
From Newton’s law, force on a body of mass m is F = GMm/R². Also F = mg. Equating both, mg = GMm/R², hence g = GM/R². Thus acceleration due to gravity depends on Earth’s mass and radius, while G remains constant everywhere.
Q7. What is simple harmonic motion? Describe the simple pendulum and derive its time period.
Simple harmonic motion is oscillatory motion where acceleration is proportional to displacement and directed towards mean position. A simple pendulum has a bob suspended by a light string. For small oscillations, T = 2π√(L/g), where L is length and g is gravity.
Q8. Define specific heat and latent heat. How is the latent heat of ice determined?
Specific heat is heat needed to raise unit mass by 1°C. Latent heat is heat absorbed or released during change of state without temperature change. Ice latent heat is found by mixing known ice mass with warm water in a calorimeter and applying heat balance.
Q9. Explain the three modes of heat transmission: conduction, convection, and radiation.
Conduction transfers heat through direct contact of particles, mainly in solids. Convection transfers heat by movement of fluids. Radiation transfers heat as electromagnetic waves without a medium. All three modes occur in agricultural systems such as soil heating, drying, and greenhouse temperature control.
Q10. State Newton's law of cooling. What are good and bad conductors of heat?
Newton’s law of cooling states that rate of cooling is proportional to temperature difference between body and surroundings. Good conductors allow heat to pass quickly, e.g., copper and aluminium. Bad conductors resist heat flow, e.g., wood, straw, and air, used in insulation.
Q11. Explain rectilinear propagation of light with the example of a pinhole camera.
Rectilinear propagation means light travels in straight lines in a uniform medium. In a pinhole camera, light from an object passes through a small hole and forms an inverted real image on a screen. This proves light travels straight and helps explain shadows.
Q12. What is dispersion of light? Describe the reflection of light through a prism.
Dispersion is splitting of white light into constituent colours due to different refractive indices. When light passes through a prism, it bends and separates into a spectrum. Reflection through a prism follows laws of reflection, with angle of incidence equal to angle of reflection.
Q13. Describe the defects of the human eye (myopia, hypermetropia) and their correction.
Myopia is short-sightedness; distant objects appear blurred. It is corrected by a concave lens. Hypermetropia is long-sightedness; near objects appear blurred. It is corrected by a convex lens. These defects arise due to changes in eyeball length or lens focal length.
Q14. State Ohm's law. Explain the grouping of resistances in series and parallel.
Ohm’s law states that current is directly proportional to potential difference at constant temperature, V = IR. In series, resistances add: R = R1 + R2 + R3. In parallel, reciprocal resistances add: 1/R = 1/R1 + 1/R2 + 1/R3.
Q15. What is the heating effect of electric current? State Joule's law of heating.
When current flows through a resistance, electrical energy converts into heat. Joule’s law states heat produced is proportional to square of current, resistance, and time: H = I²Rt. This principle is used in heaters, irons, and agricultural drying equipment.
Section B: Agriculture Chemistry
Q16. Describe Bohr's atomic model. How are electrons distributed according to Bohr-Bury rules?
Bohr proposed that electrons revolve in fixed circular orbits around the nucleus without losing energy. Bohr-Bury rules state maximum electrons in a shell is 2n², outer shell has maximum eight, and electrons fill inner shells first. These rules explain atomic stability and chemical behaviour.
Q17. Differentiate between electrovalent, covalent, and co-ordinate bonds with examples.
Electrovalent bonds form by transfer of electrons, e.g., NaCl. Covalent bonds form by sharing electrons, e.g., H₂O. Co-ordinate bonds form when one atom donates an electron pair, e.g., NH₄⁺. These bonds influence solubility, stability, and nutrient behaviour in soil.
Q18. Explain the ionic product of water. How is pH determined and what is its nutritional importance in soil?
Ionic product of water is Kw = [H⁺][OH⁻] = 10⁻¹⁴ at 25°C. pH is negative logarithm of hydrogen ion concentration. Soil pH affects nutrient availability; most crops grow best near pH 6.5–7.5, where nutrients remain soluble and available.
Q19. What are colloids? Differentiate between lyophilic and lyophobic colloids.
Colloids are mixtures with particles between true solution and suspension. Lyophilic colloids have strong affinity for dispersion medium and are stable, e.g., starch in water. Lyophobic colloids have little affinity and are less stable, e.g., gold sol. Soil colloids affect fertility.
Q20. Define hydrolysis and neutralisation. Write a brief note on the solubility product.
Hydrolysis is reaction of salt with water producing acidic or basic solution. Neutralisation is reaction of acid and base forming salt and water. Solubility product is the product of ion concentrations in saturated solution; it predicts precipitation and nutrient availability in soil.
Q21. Explain the buffer solution and its significance in agricultural chemistry.
A buffer solution resists change in pH on adding small amounts of acid or base. It contains weak acid and its salt, or weak base and its salt. In agriculture, buffers stabilise soil pH, improve nutrient availability, and support healthy crop growth and microbial activity.
Q22. What is radioactivity? Describe atomic disintegration and its types.
Radioactivity is spontaneous emission of radiation from unstable nuclei. Atomic disintegration involves emission of alpha particles, beta particles, or gamma rays. Alpha emission reduces mass and atomic number; beta changes neutron-proton ratio; gamma releases energy without changing mass or charge.
Q23. Discuss the characteristics of ionic theory and its uses in agriculture.
Ionic theory states that electrolytes dissociate into ions in solution, conduct electricity, and show colligative properties. In agriculture, it explains fertilizer dissolution, soil nutrient availability, pH, salinity, and ion exchange. It helps manage irrigation water quality and balanced fertilization.
Q24. Write a short note on the protective action of colloids.
Protective action of colloids means lyophilic colloids coat lyophobic particles and prevent coagulation. This increases stability of suspensions. In soil, organic colloids protect clay particles and improve structure. In industry, protective colloids stabilise emulsions and formulations used in agriculture.
Q25. Explain the concept of neutralisation with a suitable agricultural example.
Neutralisation is reaction between acid and base producing salt and water. In agriculture, lime is added to acidic soil; it neutralises excess hydrogen ions and raises pH. This improves nutrient availability, microbial activity, and crop yield. Gypsum can reclaim sodic soils similarly.
Section C: Agriculture Mathematics
Q26. Define trigonometry. State the simple trigonometric ratios and their basic applications.
Trigonometry studies relationships between angles and sides of triangles. Basic ratios are sine, cosine, and tangent: sinθ = perpendicular/hypotenuse, cosθ = base/hypotenuse, tanθ = perpendicular/base. It is used in land measurement, irrigation slope, and machinery design.
Q27. Explain the distance formula in analytical geometry.
The distance between two points (x₁, y₁) and (x₂, y₂) is √[(x₂−x₁)² + (y₂−y₁)²]. It is derived from Pythagoras’ theorem. It helps calculate field lengths, plot boundaries, and distances on agricultural maps and graphs.
Q28. What is a matrix? Explain the addition and subtraction of matrices.
A matrix is a rectangular arrangement of numbers in rows and columns. Addition and subtraction are possible only for matrices of the same order. Corresponding elements are added or subtracted. Matrices are useful in solving agricultural production, cost, and resource allocation problems.
Q29. Define determinants (up to 3rd order) and explain their evaluation.
A determinant is a scalar value obtained from a square matrix. A 2nd-order determinant is ad − bc. A 3rd-order determinant is expanded along a row or column using minors and cofactors. Determinants help solve linear equations and find matrix inverses.
Q30. State the permutation and combination formulae (nPr and nCr) with simple examples.
Permutation arranges objects where order matters: nPr = n!/(n−r)!. Combination selects objects where order does not matter: nCr = n!/[r!(n−r)!]. For example, arranging 3 crops in 2 positions gives 6 permutations; selecting 2 from 3 gives 3 combinations.
Q31. Find the area of a triangle using mensuration formulae.
Area of a triangle is ½ × base × height. Using sides, Heron’s formula gives area = √[s(s−a)(s−b)(s−c)], where s is semi-perimeter. These formulae help calculate plot areas, field sections, and land measurement in agriculture.
Q32. Explain the concept of integration of simple functions.
Integration is the inverse process of differentiation; it finds area under curves and total accumulation. Simple rules include ∫xⁿ dx = xⁿ⁺¹/(n+1) + C and ∫k dx = kx + C. It is used in growth, yield, and resource calculations.
Q33. What is the arithmetic progression (AP)? Give a simple example.
An arithmetic progression is a sequence in which each term differs from the previous term by a constant common difference. Example: 2, 5, 8, 11, … has common difference 3. The nth term is a + (n−1)d. AP helps in crop yield and cost estimation.
Q34. Define a function and a variable in mathematics.
A function relates each input to exactly one output, e.g., y = f(x). A variable is a symbol that represents a changing quantity, such as x or y. Functions and variables model crop growth, input-output relationships, and agricultural economics.
Q35. Explain the method of finding the inverse of a matrix (up to 3rd order) by the adjoint method.
For a square matrix A, inverse A⁻¹ = adj(A)/|A|, provided |A| ≠ 0. Find cofactors, transpose to get adjoint, then divide by determinant. This method solves simultaneous equations used in farm planning and resource allocation.
Section D: Agriculture, Botany & Zoology
Q36. Define tillage. List the main tillage operations (ploughing, harrowing, interculture).
Tillage is mechanical manipulation of soil to prepare seedbed and improve growth. Main operations include ploughing for primary loosening, harrowing for clod breaking and levelling, and interculture for weed control and aeration between crop rows. Proper tillage improves water and air movement.
Q37. Name the major and minor plant nutrients. Why are they essential for crops?
Major nutrients are nitrogen, phosphorus, potassium, calcium, magnesium, and sulphur. Minor nutrients include iron, manganese, zinc, copper, boron, and molybdenum. They are essential for growth, chlorophyll formation, enzyme activity, root development, flowering, and grain filling.
Q38. Differentiate between organic manures (FYM, compost) and inorganic fertilizers.
Organic manures such as FYM and compost are bulky, slow-release, and improve soil structure and microbial activity. Inorganic fertilizers are concentrated, quick-acting, and supply specific nutrients. Both are needed for balanced crop nutrition and sustainable soil fertility.
Q39. What are weeds? Describe the mechanical, biological, and chemical methods of weed control.
Weeds are unwanted plants competing with crops for water, nutrients, and light. Mechanical control uses hoeing and hand weeding. Biological control uses insects or bio-agents. Chemical control uses herbicides. Integrated weed management combines all methods for effective, economical control.
Q40. Explain the need and sources of irrigation and drainage in agriculture.
Irrigation supplies water for crop growth during deficient rainfall. Sources include canals, wells, tanks, and tube wells. Drainage removes excess water to prevent waterlogging and salinity. Both are essential for healthy roots, nutrient uptake, and stable crop yields.
Q41. Define crop rotation. What are the principles and importance of mixed cropping?
Crop rotation is growing different crops in sequence on the same field. Principles include fertility balance, pest break, and soil improvement. Mixed cropping grows two or more crops together to reduce risk, use resources efficiently, and increase total farm income.
Q42. Describe the cultivation of paddy (rice) with respect to land preparation, sowing, and irrigation.
Paddy requires fine puddled soil. Land is ploughed, puddled, and levelled. Sowing is done by nursery transplanting or direct seeding. Irrigation is maintained as shallow standing water during growth. Proper water management and timely weeding give good rice yield.
Q43. What is horticulture? Explain the planting systems and methods of pruning.
Horticulture is cultivation of fruits, vegetables, flowers, and ornamental plants. Planting systems include square, rectangular, triangular, and hexagonal. Pruning removes unwanted branches to improve shape, light, and fruit quality. It includes heading back and thinning out.
Q44. Describe the propagation of plants by cutting, budding, and grafting.
Cutting propagates plants from stem, root, or leaf pieces. Budding transfers a single bud to rootstock. Grafting joins scion and rootstock so they grow together. These methods produce true-to-type plants, improve disease resistance, and shorten the juvenile period.
Q45. Name two important breeds of cows and buffaloes. What is a balanced ration?
Important cow breeds include Sahiwal and Red Sindhi; buffalo breeds include Murrah and Mehsana. A balanced ration supplies all nutrients in correct proportion for maintenance and production. It includes roughage, concentrates, minerals, and water for healthy livestock.
Q46. Explain the composition of cow milk and how it is tested using a lactometer.
Cow milk contains water, fat, protein, lactose, minerals, and vitamins. A lactometer measures milk density. Pure milk has a specific range; added water lowers density. The lactometer reading, along with fat test, helps judge milk quality and adulteration.
Q47. Describe the preparation of butter, ghee, and curd (dahi) from milk.
Curd is made by adding lactic culture to warm milk and incubating it. Butter is obtained by churning cream. Ghee is prepared by heating butter to remove moisture and solids. These products improve milk preservation, nutrition, and farm income.
Q48. What are the common diseases of cattle? How can they be prevented and controlled?
Common cattle diseases include foot-and-mouth disease, mastitis, anthrax, and bloat. Prevention includes vaccination, clean sheds, balanced feed, and safe water. Control needs early diagnosis, isolation, veterinary treatment, and proper disposal of infected material.
Q49. Name important poultry breeds. Explain the natural and artificial methods of hatching eggs.
Important poultry breeds include Aseel, Kadaknath, Leghorn, and Rhode Island Red. Natural hatching uses a broody hen to incubate eggs. Artificial hatching uses incubators with controlled temperature and humidity. Both require fertile eggs and proper turning for good hatchability.
Q50. What is the main function of Krishi Vigyan Kendras (KVKs) in agricultural development?
Krishi Vigyan Kendras conduct frontline demonstrations, train farmers, and transfer improved technologies. They provide advisory services, test technologies, and link farmers with research institutions. KVKs promote sustainable farming, livestock, horticulture, and rural income through practical, location-specific support.
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