General Science: Notes और MCQ Practice

आसान भाषा में

Railway exams में General Science का game direct facts और basic concepts पर टिका होता है। यहाँ deep research नहीं, बल्कि everyday science, standard SI units, basic numerical formulas और human biology से सवाल आते हैं। Class 9th-10th level की Physics, Chemistry और Biology को smart revision से master किया जा सकता है।

Important Formulas & Rules

• Ohm's Law: V = I × R (Voltage = Current × Resistance)
• Kinetic Energy (KE): KE = 1/2 × m × v² | Potential Energy (PE): PE = m × g × h
• Work Done (W): W = F × s × cos(θ) [Unit: Joule]
• Power (P): P = Work ÷ Time = V × I [Unit: Watt]
• Mirror Formula: 1/f = 1/v + 1/u | Lens Formula: 1/f = 1/v − 1/u
• pH Scale: Acidic < 7, Neutral = 7, Basic > 7 (Human Blood = 7.4)

2 Quick Tricks

1. Vitamins की Solubility Trick: याद रखो 'KEDA' (Vitamin K, E, D, A) Fat-soluble होते हैं। बाकी बचे Vitamins B & C Water-soluble होते हैं (Trick: WBC = Water soluble B & C).
2. Sound Waves की Speed: Sound को medium चाहिए (Vacuum में speed = 0)। Speed का order याद रखें: Solid > Liquid > Gas (Steel में fastest, Air में slow).

2 Common Mistakes

1. Mass vs Weight का Confusion: Mass हमेशा constant रहता है (चाहे Earth हो या Moon)। Weight gravity पर depend करता है (W = m × g)। Moon पर Weight 1/6th होता है, Mass नहीं!
2. Formula Signs में Mix-up: Lens Formula में minus आता है (1/f = 1/v − 1/u) और Mirror Formula में plus आता है (1/f = 1/v + 1/u)—exam hall की हड़बड़ी में sign swap मत करना!

General Science Study Notes for RRB NTPC Graduate Exam

1. Concept (Simple Explanation)

In the RRB NTPC examination, General Science tests your understanding of everyday scientific principles across three core domains: Physics, Chemistry, and Biology (typically based on the NCERT Class 9 and 10 curriculum).

• Physics explores matter, energy, and forces. For RRB NTPC, focus heavily on everyday mechanics (motion, work, energy, gravitation), light (mirrors and lenses), electricity, sound, and SI units.
• Chemistry deals with the composition, properties, and reactions of substances. High-yield areas include the Periodic Table, chemical formulas of everyday compounds, acids, bases, salts, and common metals/non-metals.
• Biology is the study of living organisms. Questions consistently target human physiology (digestive, circulatory, and nervous systems), cell biology, infectious diseases, and vitamins/nutrients.

2. Important Formulas, Rules, and Facts

A. Physics Formulas & Laws

• Speed: Speed = Distance ÷ Time
• Acceleration (a): a = (v − u) ÷ t (where v = final velocity, u = initial velocity, t = time)
• Equations of Motion:
• v = u + at
• s = ut + (1 ÷ 2) × a × t²
• v² = u² + 2as
• Force (F): Force = Mass (m) × Acceleration (a) (SI unit: Newton, N)
• Work Done (W): W = Force (F) × Displacement (s) × cos(θ) (SI unit: Joule, J)
• Kinetic Energy (KE): KE = (1 ÷ 2) × m × v²
• Potential Energy (PE): PE = m × g × h (where g ≈ 9.8 m/s² or 10 m/s²)
• Power (P): Power = Work Done ÷ Time (SI unit: Watt, W; 1 Horsepower = 746 W)
• Ohm's Law: Voltage (V) = Current (I) × Resistance (R) (SI unit of R: Ohm, Ω)
• Lens / Mirror Power (P): P = 1 ÷ Focal Length (f in meters) (SI unit: Dioptre, D)

B. Chemistry Essentials

• pH Scale:
• pH < 7: Acidic (e.g., Gastric juice ≈ 1.2 to 2.0; Lemon juice ≈ 2.2)
• pH = 7: Neutral (Pure water)
• pH > 7: Basic/Alkaline (e.g., Human blood ≈ 7.35 to 7.45; Milk of Magnesia ≈ 10.5)
• Common Chemical Names and Formulas:
• Baking Soda: Sodium Bicarbonate (NaHCO₃)
• Washing Soda: Sodium Carbonate Decahydrate (Na₂CO₃·10H₂O)
• Bleaching Powder: Calcium Hypochlorite (CaOCl₂)
• Plaster of Paris (POP): Calcium Sulphate Hemihydrate (CaSO₄·0.5H₂O)
• Gypsum: Calcium Sulphate Dihydrate (CaSO₄·2H₂O)
• Laughing Gas: Nitrous Oxide (N₂O)
• Rusting of Iron: Requires both Oxygen (O₂) and Moisture (H₂O)

C. Biology Essentials

• Cell Biology:
• Mitochondria: "Powerhouse of the cell" (produces ATP)
• Ribosomes: Site of protein synthesis
• Lysosomes: "Suicidal bags" of the cell
• Human Blood:
• Universal Donor: O Negative (O−)
• Universal Recipient: AB Positive (AB+)
• Normal Blood Pressure: 120/80 mm Hg
• Vitamins and Deficiency Diseases:
• Vitamin A (Retinol) → Night Blindness, Xerophthalmia
• Vitamin B1 (Thiamine) → Beriberi
• Vitamin C (Ascorbic acid) → Scurvy
• Vitamin D (Calciferol) → Rickets (in children), Osteomalacia (in adults)
• Vitamin K (Phylloquinone) → Failure of blood clotting

3. Solved Examples (Exam Style)

Example 1 (Physics - Kinetic Energy)

Question: A car of mass 800 kg is moving with a uniform velocity of 20 m/s. What is its kinetic energy?

(A) 80,000 J

(B) 160,000 J

(C) 320,000 J

(D) 16,000 J

Solution:

• Step 1: Identify given values:
• Mass (m) = 800 kg
• Velocity (v) = 20 m/s
• Step 2: Apply the formula for Kinetic Energy:
• KE = (1 ÷ 2) × m × v²
• Step 3: Calculate:
• KE = (1 ÷ 2) × 800 × (20)²
• KE = 400 × 400 = 160,000 J (or 160 kJ)
• Correct Answer: (B) 160,000 J

Example 2 (Physics - Power of Lens)

Question: A person is prescribed a convex lens with a focal length of +25 cm. What is the power of this lens?

(A) +0.04 D

(B) +4.0 D

(C) −4.0 D

(D) +2.5 D

Solution:

• Step 1: Convert focal length from centimeters to meters:
• f = +25 cm = 25 ÷ 100 m = +0.25 m
• Step 2: Apply the Power formula:
• P = 1 ÷ f (in meters)
• Step 3: Calculate:
• P = 1 ÷ 0.25 = +4 D
• Note: Convex lenses always have positive focal length and power; concave lenses have negative.
• Correct Answer: (B) +4.0 D

Example 3 (Physics - Ohm's Law)

Question: An electric heater is connected to a 220 V supply line and draws a current of 5 A. What is the resistance of the heater element?

(A) 44 Ω

(B) 110 Ω

(C) 1100 Ω

(D) 22 Ω

Solution:

• Step 1: Identify given values:
• Potential Difference (V) = 220 V
• Current (I) = 5 A
• Step 2: Apply Ohm's Law:
• V = I × R ⇒ R = V ÷ I
• Step 3: Calculate:
• R = 220 ÷ 5 = 44 Ω
• Correct Answer: (A) 44 Ω

Example 4 (Biology - Vitamins & Diseases)

Question: Which of the following vitamins is water-soluble, and its deficiency leads to bleeding gums?

(A) Vitamin A

(B) Vitamin D

(C) Vitamin K

(D) Vitamin C

Solution:

• Step 1: Classify solubility:
• Fat-soluble vitamins: A, D, E, K
• Water-soluble vitamins: B-complex, C
• Step 2: Identify the disease symptom:
• Bleeding gums is a classic sign of Scurvy, which is caused by a deficiency of Vitamin C (Ascorbic acid).
• Correct Answer: (D) Vitamin C

4. Shortcuts and Tricks

1. Vitamin Solubility Mnemonic:

• Fat-soluble: Remember the word "KEDA" (Vitamins K, E, D, A are fat-soluble).
• Water-soluble: The remaining ones, B and C, dissolve in water (Think: Water = B & C).

1. Eye Defects & Corrective Lenses:

• Myopia (Short-sightedness): Shorter name → Uses Concave lens (caves in).
• Hypermetropia (Far-sightedness): Longer name → Uses Convex lens.

1. Electromagnetic Spectrum Order (Decreasing Wavelength / Increasing Frequency):

• Radio → Microwave → Infrared → Visible → Ultraviolet → X-ray → Gamma
• Mnemonic: Rich Men In Vegas Use Xpensive Gadgets.

1. Work Done Zero Conditions:

• In physics, Work = 0 if:
• Displacement = 0 (e.g., pushing a fixed wall).
• Angle θ = 90° (e.g., a porter carrying a load on his head and walking horizontally on level ground; gravity acts downward at 90° to horizontal motion).

5. Common Mistakes to Avoid

• Confusing Mass and Weight:
• Mass is constant everywhere (measured in kg, scalar quantity).
• Weight varies with gravity: Weight = m × g (measured in Newtons, vector quantity). At the center of the Earth, weight is 0, but mass is not 0.
• Focal Length Units in Lens Power:
• Always convert focal length into meters before using P = 1 ÷ f. Dividing by centimeters gives the wrong answer.
• Baking Soda vs. Washing Soda:
• Baking soda has hydrogen: Sodium Bicarbonate (Bi = buy food to bake).
• Washing soda has 10 water molecules: Sodium Carbonate Decahydrate.
• Speed of Sound in Different Media:
• Sound requires a medium and cannot travel in a vacuum.
• Speed order: Solids > Liquids > Gases (Fastest in solids like steel/aluminum, slowest in gases). Do not confuse this with light, which travels fastest in a vacuum.