General Science
Syllabus weight
General Science at class 9–10 level: physics (motion, force, work and energy, light, electricity, sound), chemistry (matter, atoms and molecules, acids-bases-salts, metals, carbon compounds) and biology (cell, tissues, nutrition, human body systems, diseases, plant reproduction). Questions are usually one-step conceptual or one-step numerical.
Rules worth memorising
- Newton's laws; F = ma; equations of motion v = u + at and s = ut + ½at².
- Work = force × displacement; power = work ÷ time; 1 kWh = 3.6 × 10⁶ J.
- Ohm's law V = IR; series R = R₁ + R₂; parallel 1/R = 1/R₁ + 1/R₂; P = VI = V²/R.
- pH below 7 is acidic, above 7 basic; acids turn blue litmus red, bases turn red litmus blue.
- Photosynthesis needs chlorophyll, carbon dioxide, water and sunlight; respiration releases stored energy.
Worked example
An electric bulb is rated 60 W at 220 V. Find its resistance and current. P = V²/R, so R = V²/P = (220 × 220)/60 = 806.7 Ω. I = P/V = 60/220 = 0.27 A. Reasoning: the rating pair gives resistance first, and current follows directly. In practice a filament's resistance rises with temperature, but the exam expects the constant-resistance calculation.
Traps
- Mixing scalar and vector quantities; distance versus displacement, speed versus velocity.
- Unit slips: centimetres to metres, minutes to seconds.
- Confusing antibiotics (which act on bacteria) with antivirals, and vaccines with antibiotics.
- "Which is absent in an animal cell" questions - cell wall, chloroplast and a large central vacuole are plant features.