Complete Class 12 Physics Formulas – All Chapters

CBSE Class 12 Physics Formulas Chapters wise

1. Electrostatics

Concept	Formula	Description	SI Unit
Coulomb’s Law	F = kq₁q₂/r²	Force between two point charges; k = 9×10⁹ N·m²/C²	Newton (N)
Electric Field	E = F/q = kQ/r²	Force per unit positive test charge	N/C or V/m
Electric Potential	V = kQ/r	Work done per unit charge	Volt (V)
Potential Energy	U = kq₁q₂/r	Energy of system of two charges	Joule (J)
Electric Flux	Φ = E·A·cosθ	Total field lines through a surface	N·m²/C
Gauss’s Law	Φ = q_enc/ε₀	Net flux = enclosed charge / ε₀	N·m²/C
Capacitance	C = Q/V	Charge stored per unit voltage	Farad (F)
Parallel Plate Cap.	C = ε₀A/d	A = area, d = separation	Farad (F)
Energy in Capacitor	U = ½CV² = Q²/2C	Electrostatic energy stored	Joule (J)
Capacitors in Series	1/C = 1/C₁+1/C₂+…	Equivalent capacitance (series)	Farad (F)
Capacitors Parallel	C = C₁+C₂+…	Equivalent capacitance (parallel)	Farad (F)
Dielectric Effect	C’ = KC = Kε₀A/d	K = dielectric constant	Farad (F)

2. Current Electricity

Concept	Formula	Description	SI Unit
Ohm’s Law	V = IR	Voltage = Current × Resistance	Volt (V)
Resistance	R = ρL/A	ρ = resistivity, L = length, A = area	Ohm (Ω)
Resistors Series	R = R₁+R₂+…	Series combination	Ohm (Ω)
Resistors Parallel	1/R = 1/R₁+1/R₂+…	Parallel combination	Ohm (Ω)
Electric Power	P = VI = I²R = V²/R	Rate of energy dissipation	Watt (W)
Electric Energy	E = Pt = VIt	Energy consumed	Joule (J)
Current Density	J = I/A = σE	σ = conductivity	A/m²
Drift Velocity	vd = I/(nAe)	n = number density of electrons	m/s
EMF & Int. Resistance	V = E – Ir	E = EMF, r = internal resistance	Volt (V)
Kirchhoff’s Voltage	ΣV = 0 (closed loop)	Sum of potentials in any loop = 0	Volt (V)
Kirchhoff’s Current	ΣI = 0 (junction)	Sum of currents at junction = 0	Ampere (A)
Wheatstone Bridge	P/Q = R/S	Balance condition	Dimensionless

3. Magnetic Effects of Current

Concept	Formula	Description	SI Unit
Biot–Savart Law	dB = μ₀Idlsinθ/4πr²	Magnetic field due to current element	Tesla (T)
Field Due to Wire	B = μ₀I/2πr	Long straight current-carrying wire	Tesla (T)
Field at Centre (Circle)	B = μ₀I/2r	Centre of circular current loop	Tesla (T)
Ampere’s Law	∮B·dl = μ₀I	Relates B to enclosed current	Tesla·m
Solenoid Field	B = μ₀nI	n = turns per unit length	Tesla (T)
Toroid Field	B = μ₀NI/2πr	N = total turns	Tesla (T)
Lorentz Force	F = q(v×B)	Force on moving charge in B-field	Newton (N)
Force on Wire	F = BILsinθ	L = length, θ = angle with B	Newton (N)
Torque on Loop	τ = NIAB sinθ	N turns, area A in field B	N·m
Magnetic Moment	M = NIA	Of a current-carrying loop	A·m²
Cyclotron Frequency	f = qB/2πm	Frequency of circular motion	Hertz (Hz)
Radius (Cyclotron)	r = mv/qB	Radius of circular path	Meter (m)

4. Electromagnetic Induction

Concept	Formula	Description	SI Unit
Magnetic Flux	Φ = BAcosθ	Flux through area A	Weber (Wb)
Faraday’s Law	EMF = -dΦ/dt	Induced EMF = rate of change of flux	Volt (V)
Lenz’s Law	Opposes cause	Induced current opposes change in flux	—
Motional EMF	EMF = BLv	Rod moving with velocity v	Volt (V)
Self-Inductance	EMF = -L(dI/dt)	L = self-inductance	Henry (H)
Mutual Inductance	EMF = -M(dI/dt)	M = mutual inductance	Henry (H)
Energy in Inductor	U = ½LI²	Energy stored in inductor	Joule (J)
Transformers	Vs/Vp = Ns/Np	Ideal transformer ratio	Dimensionless

5. Alternating Current (AC)

Concept	Formula	Description	SI Unit
RMS Voltage	Vrms = V₀/√2	Root mean square value	Volt (V)
RMS Current	Irms = I₀/√2	Root mean square current	Ampere (A)
Inductive Reactance	XL = ωL = 2πfL	Opposition by inductor	Ohm (Ω)
Capacitive Reactance	XC = 1/ωC	Opposition by capacitor	Ohm (Ω)
Impedance (RLC)	Z = √(R²+(XL-XC)²)	Total opposition to AC	Ohm (Ω)
Power in AC	P = VrmsIrmscosφ	cosφ = power factor	Watt (W)
Resonant Frequency	f₀ = 1/(2π√LC)	When XL = XC	Hertz (Hz)
Quality Factor	Q = ω₀L/R	Sharpness of resonance	Dimensionless

6. Optics (Ray & Wave)

Concept	Formula	Description	SI Unit
Snell’s Law	n₁sinθ₁ = n₂sinθ₂	Refraction at interface	Dimensionless
Mirror Formula	1/v + 1/u = 1/f	u=object dist., v=image dist.	—
Lens Formula	1/v – 1/u = 1/f	Thin lens formula	—
Magnification (Mirror)	m = -v/u	Linear magnification	Dimensionless
Lens Maker’s Formula	1/f = (n-1)[1/R₁-1/R₂]	Radii of curvature R₁, R₂	m⁻¹
Power of Lens	P = 1/f (metres)	In diopters	Diopter (D)
Critical Angle	sinC = 1/n	For total internal reflection	Degree
Refractive Index	n = c/v	c = speed of light in vacuum	Dimensionless
Young’s Double Slit	β = λD/d	Fringe width; D = dist., d = slit sep.	Meter (m)
Path Difference	Δ = nλ (bright)	Constructive interference condition	Meter (m)
Resolving Power	θ = 1.22λ/D	Rayleigh criterion	Radian
Diffraction (single slit)	sinθ = mλ/a	First minimum condition	—

7. Dual Nature of Matter & Radiation

Concept	Formula	Description	SI Unit
Photon Energy	E = hf = hc/λ	h = 6.626×10⁻³⁴ J·s	Joule (J)
Photoelectric Effect	KEmax = hf – φ	φ = work function	Joule (J)
Threshold Frequency	f₀ = φ/h	Minimum frequency for emission	Hertz (Hz)
de Broglie Wavelength	λ = h/mv = h/p	Wave nature of particles	Meter (m)
Einstein’s Photoelectric	eV₀ = hf – φ	V₀ = stopping potential	Volt (V)
Momentum of Photon	p = h/λ = E/c	Photon momentum	kg·m/s

8. Atoms & Nuclei

Concept	Formula	Description	SI Unit
Bohr’s Radius	rₙ = n²a₀ (a₀=0.529 Å)	Radius of nth orbit in H-atom	Angstrom (Å)
Bohr’s Energy	Eₙ = -13.6/n² eV	Energy of nth orbit	eV
Energy Emitted	E = E₂ – E₁ = hf	Photon emitted during transition	Joule (J)
Rydberg Formula	1/λ = R(1/n₁²-1/n₂²)	R = 1.097×10⁷ m⁻¹	m⁻¹
Nuclear Radius	R = R₀A^(1/3)	R₀ = 1.2×10⁻¹⁵ m	Meter (m)
Mass-Energy Equiv.	E = mc²	c = 3×10⁸ m/s	Joule (J)
Binding Energy	BE = [Zmp+(A-Z)mn-M]c²	Z=protons, A=mass number	MeV
Radioactive Decay	N = N₀e^(-λt)	λ = decay constant	Atoms
Half-Life	T½ = 0.693/λ	Time for N to reduce to N/2	Second (s)
Activity	A = λN = A₀e^(-λt)	Decays per second	Becquerel (Bq)

9. Semiconductor Electronics

Concept	Formula	Description	SI Unit
Current in Diode	I = I₀(e^(V/ηVT)-1)	Shockley diode equation	Ampere (A)
Transistor Current	IC = βIB	β = current gain (CE config)	Ampere (A)
Transistor Gain	β = IC/IB	Common emitter current gain	Dimensionless
α (CB gain)	α = IC/IE = β/(1+β)	Common base current gain	Dimensionless
Voltage Gain	AV = β × (RC/Rin)	Amplifier voltage gain	Dimensionless
Logic: NOT Gate	Y = Ā	Output is complement of input	—
Logic: AND Gate	Y = A·B	Output is 1 only if both inputs 1	—
Logic: OR Gate	Y = A+B	Output is 1 if any input is 1	—
Logic: NAND Gate	Y = (A·B)̄	NOT AND (universal gate)	—
Logic: NOR Gate	Y = (A+B)̄	NOT OR (universal gate)	—

10. Communication Systems

Concept	Formula	Description	SI Unit
Modulation Index	m = Am/Ac	Am = message, Ac = carrier amplitude	Dimensionless
AM Bandwidth	BW = 2fm	fm = message signal frequency	Hertz (Hz)
Channel Capacity	C = B·log₂(1+S/N)	Shannon-Hartley theorem	bits/s
Range of Antenna	d = √(2Rh)	R = earth radius, h = antenna height	Meter (m)
Sky Wave Range	d = 2√(2Rh)	Maximum range for sky wave	Meter (m)

How to Remember Class 12 Physics Formulas

Remembering a large number of physics formulas can be challenging. Below are evidence-based strategies recommended by educators:

1. Understand, Don’t Just Memorize: Every formula has a physical meaning. For example, F = ma tells us that force causes acceleration proportional to mass. Understanding the concept makes recall effortless.
2. Create a Dedicated Formula Notebook: Write each formula chapter-wise with one formula per line. Revisit this notebook daily during exam preparation.
3. Use Mnemonics and Acronyms: For Kirchhoff’s Laws, remember ‘KCL = currents at junctions, KVL = voltages in loops’. Create your own memory aids.
4. Solve Problems Daily: The best way to internalize formulas is to apply them. Solve at least 5–10 numerical problems per chapter.
5. Flashcard System: Write the formula on one side and its meaning/variables on the other. This spaced repetition technique improves long-term retention.
6. Group Related Formulas: Learn capacitor and resistor series/parallel formulas together since they follow opposite patterns.
7. Visualization: Draw diagrams alongside formulas (e.g., draw a capacitor when writing C = ε₀A/d).
8. Teach Others: Explaining a formula to a peer or studying in groups reinforces your own understanding significantly.

Important Physical Constants

Constant	Symbol & Value	SI Unit
Speed of Light	c = 3×10⁸ m/s	m/s
Planck’s Constant	h = 6.626×10⁻³⁴ J·s	J·s
Elementary Charge	e = 1.6×10⁻¹⁹ C	Coulomb (C)
Mass of Electron	mₑ = 9.1×10⁻³¹ kg	kg
Mass of Proton	mₚ = 1.67×10⁻²⁷ kg	kg
Permittivity (free space)	ε₀ = 8.85×10⁻¹² C²/N·m²	C²/N·m²
Permeability (free space)	μ₀ = 4π×10⁻⁷ T·m/A	T·m/A
Boltzmann’s Constant	k = 1.38×10⁻²³ J/K	J/K
Avogadro’s Number	Nₐ = 6.022×10²³ mol⁻¹	mol⁻¹
Gravitational Constant	G = 6.67×10⁻¹¹ N·m²/kg²	N·m²/kg²

Class 12 Physics Formulas related FAQs

Q1: What are the most important physics formulas for Class 12?

The most important formulas include Coulomb’s Law, Ohm’s Law, Faraday’s Laws, lens/mirror formulas, Einstein’s photoelectric equation, Bohr’s model equations, and radioactive decay laws. These cover the maximum weightage chapters in CBSE Class 12 Physics.

Q2: How can I memorize all Class 12 physics formulas?

Organize formulas chapter-wise and create flashcards. Practice daily derivations, understand the physical meaning behind each formula, use mnemonics, solve NCERT problems regularly, and revise a formula sheet before bed. Consistent revision is more effective than cramming.

Q3: Which chapter has the most formulas in Class 12 Physics?

Electrostatics, Current Electricity, and Optics typically have the highest number of formulas. Magnetism and Electromagnetic Induction also contribute significantly to the formula count in Class 12 Physics.

Q4: Is the physics formula sheet enough for board exams?

A comprehensive formula sheet is a vital reference tool, but success in boards requires understanding derivations, conceptual clarity, and regular problem-solving practice. Formula sheets supplement study — they do not replace it.

Q5: Where can I download a Class 12 Physics formula PDF?

You can download formula sheets from NCERT’s official website (ncert.nic.in), CBSE’s academic portal, or trusted educational platforms. Ensure the source aligns with the latest CBSE syllabus for accuracy.

Q6: What is the formula for energy stored in a capacitor?

The energy stored in a capacitor is given by U = ½CV² = Q²/2C = ½QV, where C is capacitance, V is voltage across the capacitor, and Q is the charge stored.

Q7: What is de Broglie’s wavelength formula and its significance?

de Broglie’s formula λ = h/mv (or h/p) states that every moving particle has an associated wavelength. It establishes the wave-particle duality of matter and is fundamental to quantum mechanics and modern physics.

Q8: How is the transformer formula derived?

The transformer equation Vs/Vp = Ns/Np is derived using Faraday’s law of electromagnetic induction. In an ideal transformer, the EMF induced in each winding is proportional to the number of turns, assuming no flux leakage.