Keyword Bank

---
target: 495+/500
author: Senior Sibling
name: keyword-bank
description: >-
  12th Grade Examiner Keyword Bank (PCMB/PCMC). 
  The specific terminology that CBSE markers look for to award full value points in high-weightage chapters.
---

# Keyword Bank — The Examiner's Secret (12th Grade)

CBSE marking schemes are structured around **Value Points**. Even if you write a brilliant explanation, you only get marks for the specific technical terms (Keywords) present in the examiner's key.

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## 🔭 Physics High-Yield Keywords

### 1. Electrostatics & Gauss Law
- **Linear/Surface/Volume Charge Density ($\lambda, \sigma, \rho$):** Must be used in continuous charge distribution derivations.
- **Electric Flux ($\Phi = \oint \vec{E} \cdot d\vec{A}$):** Mandatory integral notation.
- **Equipotential Surface:** Must mention "Work done is zero" and "Field lines are normal to surface".
- **Polarisation Vector / Dielectric Constant:** Essential for explaining capacitance changes.
- **Gaussian Surface:** Specifically mention the "Symmetry" of the surface chosen.

### 2. Current Electricity
- **Drift Velocity ($v_d$):** Must link with "Relaxation Time ($\tau$)" and "Mean Free Path".
- **Kirchhoff's Junction Rule:** Mention "Conservation of Charge".
- **Kirchhoff's Loop Rule:** Mention "Conservation of Energy".
- **Internal Resistance ($r$):** Must mention "Electrolyte" and "Concentration" dependencies.

### 3. Optics (Ray & Wave)
- **Paraxial Approximation:** The base assumption for all lens/mirror derivations.
- **Angle of Minimum Deviation ($D_m$):** Required for the prism $n$ formula.
- **Coherence / Monochromatic:** Mandatory for YDSE interference.
- **Path Difference ($\Delta x = d \sin \theta$):** The core of interference/diffraction calculations.
- **Huygens' Principle:** Mention "Primary Wavelet" and "Secondary Wavefront".

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## 🧪 Chemistry High-Yield Keywords

### 1. Organic Mechanisms
- **Nucleophilic Attack:** Mandatory for $S_N1/S_N2$ and Carbonyl addition.
- **Resonance Stabilization / Delocalization:** Why Phenols/Carboxylic acids are more acidic.
- **Inductive Effect (+I / -I):** Used to explain stability of carbocations or acidity trends.
- **Steric Hindrance:** The primary reason for $S_N2$ reactivity order in alkyl halides.
- **Racemisation / Inversion of Configuration:** Essential for stereochemistry questions.

### 2. Physical Chemistry
- **van't Hoff Factor ($i$):** Mandatory for colligative property numericals involving electrolytes.
- **Molar Conductivity ($\Lambda_m$):** Link with "Kohlrausch's Law of Independent Migration".
- **Activated Complex:** The term needed for Arrhenius theory and Collision theory.
- **Order vs Molecularity:** Use terms like "Experimental" vs "Theoretical".

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## 🧬 Biology High-Yield Keywords

### 1. Genetics & Molecular Basis
- **Semiconservative:** Mandatory term for Watson-Crick DNA replication model.
- **Promoter, Structural Gene, Terminator:** The three parts of a Transcription Unit.
- **Codon (Degenerate/Universal/Unambiguous):** Use these specific properties.
- **Pleiotropy / Polygenic Inheritance:** Technical terms for gene interaction patterns.

### 2. Biotechnology
- **Restriction Endonuclease:** "Molecular Scissors" that cut at "Palindromic Sequences".
- **rDNA (Recombinant DNA):** The core product of gene splicing.
- **Bioreactor:** Mention "Optimal Temperature, pH, and Substrate".
- **Downstream Processing:** Must use "Separation" and "Purification".

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## 📐 Mathematics High-Yield Keywords

### 1. Calculus (Integration & Diff Eq)
- **Constant of Integration ($C$):** Deducted 0.5m if missing in Indefinite Integrals.
- **Integrating Factor ($IF$):** Mandatory step for Linear Differential Equations.
- **King Property / Property IV:** State $\int_0^a f(x) dx = \int_0^a f(a-x) dx$ explicitly.
- **Point of Inflexion:** For Maxima/Minima theory.

### 2. Vectors & 3D
- **Direction Cosines vs Ratios:** Distinguish between $(l, m, n)$ and $(a, b, c)$.
- **Projection of $\vec{a}$ on $\vec{b}$:** Use the term "Scalar Projection" or "Vector Projection".
- **Skew Lines:** Lines that are "Neither intersecting nor parallel".

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## 💡 Using the `/keyword-check` Command
Before finalizing any answer, run this check. The AI will:
1. Scan your answer against this bank.
2. Flag missing high-value terms.
3. Show you exactly where to insert them for maximum marks.

**Senior Sibling Tip:** Don't just know the concept; use the **terminologies** that the NCERT uses. That is the only way to get a 100/100.