GUJCET, JEE Main and NEET · free
Class 12 Physics Formula Sheet
Class 12 physics carries the largest formula load of the two years, and most of it is electricity and magnetism. Learn each with its symbols, because the entrance paper rewrites the same relations in unfamiliar words.
37 formulas across 5 sections.
Message us and we send the printable PDF to your WhatsApp.
Electrostatics
| What | Formula | Symbols |
|---|---|---|
| Coulomb's law | F = kq₁q₂/r² | k = 1/4πε₀ = 9 × 10⁹ N m² C⁻² |
| Electric field | E = F/q = kQ/r² | unit N/C, equivalently V/m |
| Electric potential | V = kQ/r | scalar, so add algebraically |
| Potential energy | U = kq₁q₂/r | positive for like charges |
| Gauss's law | Φ = q(enclosed)/ε₀ | flux depends only on enclosed charge |
| Capacitance, parallel plate | C = ε₀A/d | with a dielectric, multiply by k |
| Energy in a capacitor | U = ½CV² = ½QV = Q²/2C | three equivalent forms |
| Capacitors in series | 1/C = 1/C₁ + 1/C₂ | opposite of the resistor rule |
| Capacitors in parallel | C = C₁ + C₂ | opposite of the resistor rule |
Current electricity
| What | Formula | Symbols |
|---|---|---|
| Ohm's law | V = IR | R = ρL/A |
| Drift velocity | I = neAvd | n electron density, e charge, A area |
| Kirchhoff's junction rule | ΣI = 0 at a junction | conservation of charge |
| Kirchhoff's loop rule | ΣV = 0 around a loop | conservation of energy |
| Wheatstone bridge, balanced | P/Q = R/S | no current through the galvanometer |
Magnetism and induction
| What | Formula | Symbols |
|---|---|---|
| Force on a charge | F = qvB sinθ | maximum when v is perpendicular to B |
| Force on a conductor | F = BIL sinθ | basis of the electric motor |
| Biot–Savart law | dB = (μ₀/4π)(I dl sinθ)/r² | μ₀ = 4π × 10⁻⁷ T m A⁻¹ |
| Field at the centre of a loop | B = μ₀I/2R | R radius of the loop |
| Faraday's law | e = −dΦ/dt | the minus sign is Lenz's law |
| Self inductance | e = −L dI/dt | L in henry |
| Transformer | Vₛ/Vₚ = Nₛ/Nₚ | step-up means more turns on the secondary |
Alternating current
| What | Formula | Symbols |
|---|---|---|
| RMS values | I(rms) = I₀/√2, V(rms) = V₀/√2 | what an AC meter reads |
| Inductive reactance | XL = 2πfL | rises with frequency |
| Capacitive reactance | XC = 1/2πfC | falls with frequency |
| Impedance | Z = √(R² + (XL − XC)²) | series LCR circuit |
| Resonant frequency | f = 1/(2π√(LC)) | at resonance Z = R and current is maximum |
| Power factor | cosφ = R/Z | power = V(rms) I(rms) cosφ |
Optics and modern physics
| What | Formula | Symbols |
|---|---|---|
| Lens maker's formula | 1/f = (n − 1)(1/R₁ − 1/R₂) | R radii of curvature |
| Lenses in contact | 1/f = 1/f₁ + 1/f₂ | powers simply add |
| Young's double slit, fringe width | β = λD/d | D slit-to-screen distance, d slit separation |
| Photoelectric equation | hν = φ + KE(max) | φ work function |
| Stopping potential | eV₀ = hν − φ | depends on frequency, not intensity |
| de Broglie wavelength | λ = h/p = h/mv | h = 6.626 × 10⁻³⁴ J s |
| Bohr quantisation | mvr = nh/2π | n principal quantum number |
| Radioactive decay | N = N₀e−λt | λ decay constant |
| Half-life | t½ = 0.693/λ | independent of the starting amount |
| Mass–energy | E = mc² | c = 3 × 10⁸ m/s |
Taught by Darshit Bhatt, founder and lead faculty at Darshit Sir Institute. Instrumentation and Control engineer, with a master's degree and a chartered degree, teaching in Paldi, Ahmedabad since 2006.
Chapter by chapter
Every chapter on its own page.
Electrostatics
Electrostatics opens Class 12 and sets the pattern for the whole year: a field, a potential, and an energy, for each of ...
Open 14 formulasCapacitance
Capacitance is where circuit questions begin. Only four ideas are needed: how capacitance is defined, what a dielectric ...
Open 16 formulasCurrent Electricity
Current electricity is the most predictable scoring chapter of Class 12. Ohm's law, the two Kirchhoff rules and the Whea...
Open 17 formulasMoving Charges and Magnetism
This chapter is where the right hand earns its marks. Every formula here has a direction attached, and the numerical par...
Open 16 formulasMagnetism and Matter
A short, mostly theoretical chapter that reliably supplies one or two marks. The bar magnet formulas mirror the electric...
Open 14 formulasElectromagnetic Induction
Induction is one sentence with many consequences: a changing magnetic flux makes an EMF, and the minus sign in Lenz's la...
Open 15 formulasAlternating Current
AC takes the DC circuit you already know and adds phase. Reactance replaces resistance for capacitors and inductors, imp...
Open 14 formulasElectromagnetic Waves
A short chapter with few formulas and reliable marks. Most questions ask for the order of the spectrum, the uses of one ...
Open 21 formulasRay Optics and Optical Instruments
Ray optics carries the most numerical marks in Class 12 physics, and nearly all of them hang on one habit: fixing the si...
Open 13 formulasWave Optics
Wave optics is where light stops being a ray and becomes a wave. Young's double slit gives the standard derivation and t...
Open 12 formulasDual Nature of Radiation and Matter
This chapter is short, conceptual, and nearly free marks if the photoelectric graphs are learned. Its central point is t...
Open 22 formulasAtoms and Nuclei
Atoms and nuclei supplies the Bohr model results and the decay laws, both of which are pure formula work. The energy lev...
Open 19 formulasSemiconductor Electronics
The last chapter of the course, and often the most scoring, because the questions repeat. Doping, the p-n junction, the ...
OpenTest yourself
Do you actually know these?
Ten questions, instant score, and a readout of which section you are losing marks on.
Ask DSI
Know the formula but not when to use it?
Tell us the subject and where you are stuck. We will tell you whether a batch helps.
Related
Keep going.
Talk to the teacher, not a counsellor.
Bring the student's last two report cards. You will get an honest read on where they stand and which batch actually helps, from the person who will do the teaching.