Interactive diagrams — Class 12 Physics

214 diagrams · tap a card, then tap any label.

Ch 1 · Electric Charges and Fields

Like charges repel, unlike charges attractFig 1.1Gold-leaf electroscopeFig 1.2Coulomb’s law: geometry and forcesFig 1.3Superposition principle: force on q₁ from many chargesFig 1.5Electric field of a point chargeFig 1.8Electric field lines of simple chargesFig 1.14Electric flux through a small areaFig 1.15–1.16Electric field of a dipole: axial and equatorial pointsFig 1.17Dipole in a uniform electric field: torqueFig 1.19Continuous charge: line, surface and volume densityFig 1.21Gauss’s law: flux through a sphere around a point chargeFig 1.22Flux of a uniform field through a closed cylinderFig 1.23Field of an infinitely long charged wire (Gauss’s law)Fig 1.26Field of a uniformly charged infinite plane sheetFig 1.27Field of a uniformly charged thin spherical shellFig 1.28

Ch 2 · Electrostatic Potential and Capacitance

Work done against the field: the idea of potentialFig 2.1–2.2How V and E of a point charge change with rFig 2.3Potential due to an electric dipoleFig 2.4Equipotential surfaces: point charge and uniform fieldFig 2.10–2.11Equipotentials: dipole and two like chargesFig 2.12Potential energy of a system of chargesFig 2.13–2.14A conductor in an external electric fieldFig 2.16–2.17Polarisation of a dielectric in an electric fieldFig 2.20–2.23The parallel plate capacitorFig 2.24–2.25Capacitors in series and in parallelFig 2.26–2.28

Ch 3 · Current Electricity

Drift of electrons and electric currentFig 3.3–3.4Resistance, length and area: R = ρl/AFig 3.2Where Ohm’s law holds — and where it failsFig 3.5–3.7How resistivity changes with temperatureFig 3.8–3.10A cell: emf and internal resistanceFig 3.12Cells in series and in parallelFig 3.13–3.14Kirchhoff’s junction rule and loop ruleFig 3.15The Wheatstone bridgeFig 3.18Kirchhoff’s rules at work: the network of NCERT Example 3.6Fig 3.17

Ch 4 · Moving Charges and Magnetism

Oersted’s discovery: field around a straight currentFig 4.1Direction of the magnetic force F = q(v × B)Fig 4.2A current-carrying wire held up by a magnetic fieldFig 4.3v along +x, B along +y: which way is the force?Fig 4.4Charge moving perpendicular to B goes in a circleFig 4.5Helical path: velocity at an angle to BFig 4.6Biot–Savart law: field of a small current elementFig 4.7Example: field of a 1 cm current elementFig 4.8Field on the axis of a circular current loopFig 4.9Magnetic field lines of a current loopFig 4.10Wire bent into a semicircle: field at the centreFig 4.11Ampère’s circuital law: loop, surface and enclosed currentFig 4.12Thick wire: B inside and outside (Ampère’s law)Fig 4.13–4.14The two right-hand thumb rulesField of a solenoid (computed from its turns)Fig 4.15Very long solenoid: Ampère’s law with loop abcdFig 4.16Force between two parallel currentsFig 4.17Torque on a rectangular current loop in a uniform BFig 4.18–4.19Moving coil galvanometer (construction)Fig 4.20Radial field: why τ = NIAB at every angleFig 4.20Galvanometer → ammeter (shunt) and voltmeter (series R)Fig 4.21–4.22Example 4.12: what a meter does to the currentFig 4.23

Ch 5 · Magnetism and Matter

Iron filings around a bar magnetFig 5.1Field lines of a bar magnetFig 5.2(a)Field lines of a finite solenoidFig 5.2(b)Electric dipole field lines (for comparison)Fig 5.2(c)Axial field of a finite solenoidFig 5.3(a)A magnetic needle in a uniform fieldFig 5.3(b)Potential energy and torque vs angleAxial and equatorial field of a bar magnetEq 5.4–5.5Example 5.2: which positions are in equilibrium?Fig 5.4Gauss’s law for magnetismFig 5.5Example 5.3: spot the wrong field linesFig 5.6H, M and B inside a solenoid with a coreEq 5.8–5.15Materials in a magnetic field: dia, para, ferroFig 5.7Magnetic domains in a ferromagnetFig 5.8Why dia- and paramagnetism happen§5.5.1–5.5.2Cutting a magnet: no isolated polesExample 5.1Compass needles around a bar magnet§5.2.1

Ch 6 · Electromagnetic Induction

Magnet and coil: direction of induced currentFig 6.1 / 6.6A moving current-carrying coil induces currentFig 6.2Experiment 6.3: pressing and releasing the keyFig 6.3Magnetic flux Φ = BA cos θFig 6.4Faraday’s law on a graph: ε = −dΦ/dtEq. 6.3Lenz’s law: loops entering and leaving a field (Example 6.4)Fig 6.7 (our drawing)Which loop gives a constant emf? (Example 6.5c)Fig 6.8 (our drawing)Polarity of a capacitor in a loop (Example 6.5d)Fig 6.9 (our version)Motional emf: rod PQ sliding on railsFig 6.10Rotating rod: emf between centre and rimFig 6.11Mutual inductance of two co-axial solenoidsFig 6.12Two concentric coils (Example 6.8)Example 6.8Self-induction: the back emf opposes every changeSection 6.7.2AC generator: coil, magnets, slip rings and brushesFig 6.13Alternating emf: ε = ε₀ sin ωtFig 6.14

Ch 7 · Alternating Current

AC voltage applied to a resistorFig 7.1 / 7.2Root mean square (rms) currentFig 7.3Phasors for an ac circuit with a resistorFig 7.4AC voltage across a pure inductor (current lags)Fig 7.5 / 7.6AC voltage across a capacitor (current leads)Fig 7.7 / 7.8Power supplied to a pure inductor averages to zeroSec 7.4Bulb and coil: effect of an iron rodFig 7.9Series LCR circuit with an ac sourceFig 7.10Phasor diagram of a series LCR circuitFig 7.11Impedance diagram (right triangle)Fig 7.12Series LCR (XC > XL): V, I phasors and graphsFig 7.13Resonance curves of a series LCR circuitFig 7.14Power factor improvement with a capacitorFig 7.15Transformer: coils on separate limbsFig 7.16(b)Transformer: coils one over the otherFig 7.16(a)Power transmission with step-up and step-down transformersSec 7.8

Ch 8 · Electromagnetic Waves

Charging capacitor: one loop, three surfaces (the puzzle)Fig 8.1E and B between the plates of a charging capacitorFig 8.2Which charges make EM waves? (and how the wave sustains itself)§8.3.1A plane EM wave: E along x, B along y, travelling along zFig 8.3E × B gives the direction of travel (Examples 8.1, 8.2)Ex 8.1, 8.2The electromagnetic spectrum (log scale)Fig 8.4 · Table 8.1Radio-wave bands: AM, short wave, TV, FM, mobile§8.4.1Ozone layer and greenhouse effect: UV, visible and infrared§8.4.3, §8.4.5How X-rays are produced (X-ray tube)§8.4.6

Ch 9 · Ray Optics and Optical Instruments

Concave mirror: real image (ray diagram)Fig 9.5Cartesian sign conventionFig 9.2Focus of concave and convex mirrorsFig 9.3Why f = R/2 (geometry)Fig 9.1, 9.4Virtual images: concave (object inside F) and convex mirrorFig 9.6Phone along the axis: distorted image (Example 9.2)Fig 9.7Refraction and reflection at an interface (Snell’s law)Fig 9.8Lateral shift through a glass slabFig 9.9Apparent depth (bottom of a tank looks raised)Fig 9.10Total internal reflection and critical angleFig 9.11Prisms that use total internal reflectionFig 9.13Optical fibre: light guided by total internal reflectionFig 9.14Refraction at a spherical surfaceFig 9.15Ray tracing: convex and concave lensFig 9.17A lens as two refracting surfaces (lens maker’s formula)Fig 9.16Power of a lensFig 9.18Two thin lenses in contactFig 9.19Example 9.8: three-lens combinationFig 9.20Refraction through a prismFig 9.21Angle of deviation vs angle of incidence (i–δ curve)Fig 9.22Simple microscope (magnifier)Fig 9.23Compound microscope (ray diagram)Fig 9.24Refracting (astronomical) telescopeFig 9.25Cassegrain reflecting telescopeFig 9.26

Ch 10 · Wave Optics

Wavefronts: spherical (near a point source) and plane (far away)Fig 10.1Huygens construction: the new wavefront is the forward envelope of the waveletsFig 10.2Huygens construction for a plane wave moving to the rightFig 10.3Refraction of a plane wave into a denser medium (Huygens ⇒ Snell’s law)Fig 10.4Refraction of a plane wave into a rarer medium (bends away from the normal)Fig 10.5Reflection of a plane wave: triangles EAC and BAC are congruent ⇒ i = rFig 10.6What a prism, a convex lens and a concave mirror do to a plane wavefrontFig 10.7Two coherent sources: crests, troughs and the lines of maximum and zero disturbanceFig 10.8, 10.10Adding two waves: in phase (path difference 2λ) and out of phase (2.5λ)Fig 10.9Two independent lamps are incoherent: intensities just add, no fringesFig 10.11Young’s double-slit arrangement and the path difference at PFig 10.12Interference fringes on the screen and the intensity I = 4I₀ cos²(πxd/λD)Fig 10.13Single slit of width a: path difference between its edges is a sin θFig 10.14Single-slit diffraction: broad central maximum, minima at θ = ±λ/a, ±2λ/a, …Fig 10.15Transverse waves: polarised (one plane) and unpolarised (random planes)Fig 10.17Two polaroids: I = I₀ cos²θ (Malus’ law)Fig 10.18Example 10.2: a polaroid P₂ rotated between crossed polaroids P₁ and P₃Example 10.2Entering a denser medium: speed and wavelength drop, frequency stays the sameEq 10.7

Ch 11 · Dual Nature of Radiation and Matter

Work function φ0 — energy pictureSec 11.2Three ways to emit electronsSec 11.2Hallwachs: zinc plate loses negative charge in UVSec 11.3.2Experimental arrangement for the photoelectric effectFig 11.1Photocurrent vs intensity of lightFig 11.2Photocurrent vs collector potential for different intensitiesFig 11.3Photocurrent vs collector potential for different frequenciesFig 11.4Stopping potential V0 vs frequency νFig 11.5Einstein's equation: hν = φ0 + KmaxSec 11.6Intensity = number of photons, frequency = energy of each photonSec 11.6–11.7How big is a de Broglie wavelength?Sec 11.8, Ex 11.3

Ch 12 · Atoms

Thomson’s plum pudding model vs Rutherford’s nuclear model§12.1Geiger–Marsden α-scattering experiment (set-up)Figs 12.1, 12.2How many α-particles scatter at each angle (Rutherford’s curve)Fig 12.3α-particle paths near a nucleus: impact parameter b and scattering angle θFig 12.4Distance of closest approach d (head-on α-particle)Example 12.2Electron orbit in hydrogen: electric force gives the centripetal force§12.2.2Why Rutherford’s atom should collapse (classical prediction)Fig 12.6Line spectrum of hydrogen: emission and absorption (visible Balmer lines)Fig 12.5Bohr orbits of hydrogen (to scale): rₙ = n²a₀§12.4Energy-level diagram of hydrogen (with Lyman, Balmer, Paschen jumps)Fig 12.7De Broglie’s standing electron wave on a Bohr orbit (n = 4)Fig 12.8Bohr’s third postulate: emission and absorption of a photon§12.4, §12.5

Ch 13 · Nuclei

Binding energy per nucleon vs mass numberFig 13.1Nuclear force: potential energy of two nucleonsFig 13.2Size of the nucleus: R = R₀A^(1/3)Section 13.3Writing a nucleus: ᴬ_Z XSection 13.2Isotopes, isobars and isotonesSection 13.2How small is the nucleus?Section 13.1Discovery of the neutron (Chadwick, 1932)Section 13.2Mass defect and binding energy of ¹⁶OSection 13.4.2Radioactivity: α, β and γ decaySection 13.6Nuclear fission of uranium-235Eq. 13.10Why fission releases about 200 MeVSection 13.7.1Why fusion needs very high temperatureSection 13.7.2The proton–proton (p, p) cycle in the SunEq. 13.14–13.15Chemical vs nuclear energy (per kg)Section 13.7Controlled fusion: holding a 10⁸ K plasmaSection 13.7.3

Ch 14 · Semiconductor Electronics: Materials, Devices and Simple Circuits

Energy bands of a semiconductor at 0 KFig 14.1Energy bands: metal, insulator, semiconductorFig 14.2Diamond-like crystal structure (Si, Ge, C)Fig 14.3Covalent bonds in Si/Ge (2-D picture)Fig 14.4Electron–hole pair and motion of a holeFig 14.5Intrinsic semiconductor at T = 0 K and T > 0 KFig 14.6n-type semiconductor: pentavalent donorFig 14.7p-type semiconductor: trivalent acceptorFig 14.8Donor and acceptor levels in the band diagramFig 14.9Formation of a p-n junctionFig 14.10Unbiased p-n junction and barrier potentialFig 14.11Semiconductor diode and its symbolFig 14.12p-n junction diode under forward biasFig 14.13p-n junction diode under reverse biasFig 14.15Forward bias: minority carrier injectionFig 14.14Circuits to study the V–I characteristicFig 14.16 (a), (b)V–I characteristic of a silicon diodeFig 14.16 (c)Diode characteristic for Example 14.4Fig 14.17Half-wave rectifierFig 14.18Full-wave (centre-tap) rectifierFig 14.19Rectifier with capacitor filterFig 14.20