CBSE · Class 12

Important Diagrams

Every must-draw diagram for Class 12 Physics and Biology. For each diagram: exactly what to label, how many marks it carries, and how frequently it appears in board exams.

Physics (12 diagrams)

Electric Charges and Fields

Electric field lines of a dipole

very high1M

What to label

Positive charge (+q)Negative charge (−q)Field lines (from + to −)Direction of arrows

💡

Lines start from + and end at −. Lines never cross. Denser lines = stronger field.

Electrostatic Potential and Capacitance

Parallel plate capacitor with dielectric

very high1M

What to label

Plates (+Q and −Q)Separation dDielectric slab (K)Electric field E

Current Electricity

Potentiometer circuit

very high2M

What to label

Main battery (driver cell)JockeyWire (400 cm)Unknown EMFGalvanometer (G)Balance point l

💡

Draw Wheatstone bridge inside if asked for EMF comparison experiment.

Moving Charges and Magnetism

Moving coil galvanometer

very high3M

What to label

Coil (rectangular)Permanent magnets (N and S)Soft iron coreSpring (for restoring torque)Pointer and scale

Electromagnetic Induction

AC Generator

very high3M

What to label

Rectangular coil (armature)Slip ringsCarbon brushesExternal resistance RMagnets N and SAxis of rotation

💡

Distinguish from DC motor: generator produces AC, motor converts electrical to mechanical.

Alternating Current

Series LCR circuit and phasor diagram

very high3M

What to label

L, C, R in seriesVoltage across each element (V_L, V_C, V_R)Phasor anglesResultant voltage VPhase angle φ

💡

V_L and V_C are anti-phase (180° apart). V_R is in phase with I.

Alternating Current

Transformer (step-up/step-down)

very high2M

What to label

Primary coil (N_p turns)Secondary coil (N_s turns)Iron core (laminated)Input voltage V_pOutput voltage V_sFlux lines

Ray Optics

Ray diagram — image formation by concave mirror

very high2M

What to label

ObjectImagePrincipal axisCentre of curvature CFocus FTwo rays (parallel→focus, through C)Image nature (real/virtual, inverted/erect)

💡

Draw for at least 3 object positions: beyond C, at C, between F and C.

Ray Optics

Refraction through prism (minimum deviation)

very high3M

What to label

Incident rayRefracted ray insideEmergent rayAngle of prism AAngle of incidence iAngle of deviation δMinimum deviation δ_m

Wave Optics

Young's Double Slit Experiment (YDSE)

very high3M

What to label

Source SSlits S₁ and S₂ScreenDistance D (slit to screen)Slit separation dCentral bright fringenth bright/dark fringe at yₙ

Semiconductor Electronics

Energy band diagrams (conductor, semiconductor, insulator)

very high2M

What to label

Valence bandConduction bandForbidden energy gap (E_g)Fermi levelArrows for electron transitions

💡

E_g: Conductor = 0 or overlapping, Semiconductor ~1 eV (Si: 1.1 eV), Insulator >3 eV.

Semiconductor Electronics

p-n Junction diode — forward and reverse bias

very high3M

What to label

p-regionn-regionDepletion layerBattery polarityDirection of conventional currentI-V characteristic curve

Biology (11 diagrams)

Sexual Reproduction in Flowering Plants

T.S. of ovary showing follicles at different stages

very high3M

What to label

Germinal epitheliumPrimary follicleGraafian follicleCorpus luteumStromaOvum

💡

Show progression from primary follicle to Graafian follicle to corpus luteum in same diagram.

Sexual Reproduction in Flowering Plants

L.S. of a flower showing parts

very high2M

What to label

PetalSepalStamen (anther + filament)Pistil (stigma + style + ovary)OvuleReceptacle

Sexual Reproduction in Flowering Plants

Pollen grain (mature — 2-celled and 3-celled)

very high2M

What to label

ExineIntineGerm poreVegetative cellGenerative cell / Male gametesPollen tube nucleus

Sexual Reproduction in Flowering Plants

Embryo sac (mature 7-celled, 8-nucleate)

very high3M

What to label

Egg cell2 synergids2 polar nuclei (or central cell)3 antipodal cellsFiliform apparatus

💡

Count carefully: 7 cells, 8 nuclei (central cell has 2 polar nuclei). Board examiners check this.

Molecular Basis of Inheritance

DNA double helix structure

very high3M

What to label

Sugar-phosphate backbone (antiparallel)Base pairs (A-T, G-C)H-bonds (2 for A-T, 3 for G-C)5' and 3' endsMajor and minor grooves

💡

Show both strands antiparallel — one 5'→3', other 3'→5'. Label clearly.

Molecular Basis of Inheritance

Replication fork / Semi-conservative replication

very high3M

What to label

Origin of replicationLeading strand (continuous)Lagging strand (Okazaki fragments)DNA polymerase IIIRNA primerDirection of synthesis (5'→3')

Molecular Basis of Inheritance

Transcription unit

high3M

What to label

Template strand (3'→5')Coding strand (5'→3')Promoter regionStructural geneTerminatorDirection of RNA synthesis

Molecular Basis of Inheritance

Lac operon structure

very high5M

What to label

Regulator gene (i)Promoter (p)Operator (o)Structural genes (z, y, a)Repressor proteinInducer (allolactose)mRNAEnzymes (β-galactosidase, permease, transacetylase)

💡

One of the most diagrammatically tested topics. Draw the 'ON' and 'OFF' states separately.

Human Reproduction

Human male reproductive system

very high3M

What to label

TestesEpididymisVas deferensSeminal vesicleProstate glandBulbourethral glandUrethraPenis

Human Reproduction

Human female reproductive system

very high3M

What to label

OvaryFallopian tube (oviduct)UterusCervixVaginaFimbriae

Ecosystem

Food chain / Ecological pyramid

very high2M

What to label

Producers (T₁)Primary consumers (T₂)Secondary consumers (T₃)Tertiary consumers (T₄)Energy values or biomass at each level10% law arrow

💡

Pyramid of energy is ALWAYS upright. Pyramid of biomass can be inverted (aquatic ecosystem).

More for CBSE Class 12

Formula Sheets →Important Derivations →Named Reactions →Previous Year Papers →Last Minute Revision →

Important Diagrams

Physics (12 diagrams)

Electric field lines of a dipole

Parallel plate capacitor with dielectric

Potentiometer circuit

Moving coil galvanometer

AC Generator

Series LCR circuit and phasor diagram

Transformer (step-up/step-down)

Ray diagram — image formation by concave mirror

Refraction through prism (minimum deviation)

Young's Double Slit Experiment (YDSE)

Energy band diagrams (conductor, semiconductor, insulator)

p-n Junction diode — forward and reverse bias

Biology (11 diagrams)

T.S. of ovary showing follicles at different stages

L.S. of a flower showing parts

Pollen grain (mature — 2-celled and 3-celled)

Embryo sac (mature 7-celled, 8-nucleate)

DNA double helix structure

Replication fork / Semi-conservative replication

Transcription unit

Lac operon structure

Human male reproductive system

Human female reproductive system

Food chain / Ecological pyramid

More for CBSE Class 12

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