Science for CDS/OTA
~10 min read
- What: CDS/OTA Science covers Physics (mechanics, optics, sound, electricity), Chemistry (atomic structure, periodic table, acids-bases, organic) and Biology (cells, human body, plants, diseases).
- Marks: ~22-28 questions × 4 = 88-112 marks in the General Knowledge paper.
- Source: NCERT Class 6-10 Science forms the backbone; selected NCERT Class 11-12 chapters add depth. 42 sub-topics route the entire CDS/OTA Science PYQ pool.
Science in the CDS/OTA Paper
Science is the second-largest GK bucket in CDS/OTA, after Geography. Questions reward conceptual clarity over rote facts — a few simple formulae (F = ma, V = IR, lens formula) and a strong grasp of biological systems will carry you through most of the paper. Physics leans toward applied mechanics, optics and electricity; Chemistry asks about pH, periodic table, acids/bases and basic organic; Biology dominates with cell biology, human anatomy and diseases.
42-Topic Syllabus
Cluster A — Mechanics & Motion (5)
Cluster B — Optics, Sound & Heat (8)
Cluster C — Electricity & Circuits (3)
Cluster D — Atomic Structure & Periodicity (4)
Cluster E — Acids, Salts & Substances (7)
Cluster F — Cell Biology (3)
Cluster G — Human Body Systems (5)
Cluster H — Plant Biology (3)
Cluster I — Health & Immunity (3)
8-Week Plan
- Week 1: Mechanics — Newton's laws, momentum, circular motion, gravity, velocity-time graphs.
- Week 2: Optics & Sound — mirrors, lenses, refraction, dispersion, sound waves, frequency.
- Week 3: Heat & Electricity — specific/latent heat, convection, resistors, circuits, safety fuses.
- Week 4: Atomic structure, isotopes, periodic table, valency.
- Week 5: Acids, bases, salts, metals, alloys, carbon allotropes, hydrocarbons, mixtures, water hardness.
- Week 6: Cell biology — organelles, membrane, plant vs animal cell. Plant biology — photosynthesis, hormones, xylem/phloem.
- Week 7: Human body — digestive, circulatory, blood, endocrine, nervous system.
- Week 8: Diseases, deficiency disorders, immunity; full PYQ revision.
Reference Books
| Book | Use |
|---|---|
| NCERT Class 6-10 Science | Core textbook — covers ~75% of CDS/OTA Science |
| NCERT Class 11 Physics (selected units) | Mechanics, optics, electricity — depth on Newton's laws and ray optics |
| NCERT Class 11 Chemistry (selected units) | Atomic structure, periodic table, chemical bonding |
| NCERT Class 11 Biology | Cell biology, plant kingdom, biomolecules |
| NCERT Class 12 Biology | Human physiology, reproduction, genetics, biotechnology, ecology |
| Lucent's General Science | Quick revision and additional CDS-style factual coverage |
| CDS/OTA Science PYQs 2015-2025 | Routed PYQ pool — practice asset |
Drill CDS/OTA Science
Topic-tagged Science mocks across all 42 sub-topics, built on a decade of CDS/OTA PYQs.
Start Free Mock TestFAQs
How many Science questions in CDS/OTA?
22-28 per paper in the General Knowledge section. Physics ~7-9, Chemistry ~6-8, Biology ~9-11 — biology dominates.
Is Class 11-12 NCERT needed?
Class 6-10 NCERT covers most of the syllabus. For deeper questions on atomic structure, biotechnology, human physiology and ray optics, add selected Class 11-12 chapters.
Which cluster has highest weightage?
Biology — especially cell biology, human body systems and diseases. Together they yield 9-11 questions per paper. Chemistry on acids/pH and metals is also high-yield.
How does CDS/OTA Science differ from NDA?
CDS/OTA Science is closer to NCERT and conceptual; NDA leans toward formula-heavy physics and chemistry. The biology depth is similar in both.
Can I skip Physics if I'm not from a science background?
Not advisable — Physics yields ~7-9 questions and a few formulae (V=IR, F=ma, lens formula) get most of them. The cost-benefit of one week on Physics is high.