Physics Equation Mechanism Class 12 Formulas and Short Notes | Complete Guide

Physics is one of the most important subjects in Class 12, especially for students preparing for board exams, competitive exams like JEE, NEET, or other entrance tests. It helps us understand the natural world through laws, equations, and mechanisms that govern motion, energy, waves, electricity, magnetism, and modern physics.

For Class 12 students, Physics Equation Mechanism Class 12 Formulas and Short Notes become extremely valuable because they allow quick revision before exams. Memorizing all derivations and formulas can be difficult, but with proper notes, you can simplify complex concepts into small, manageable chunks.

In this blog, we will provide a comprehensive list of Physics Class 12 formulas with explanations, derivations (short), and short notes to make your revision easy and effective.

Physics Equation Mechanism Class 12 Formulas and Short Notes | Complete Guide

Why Are Physics Equations and Mechanisms Important?

1. Concept Clarity – Formulas are derived from fundamental principles. Understanding the mechanism helps to avoid rote learning.

2. Exam Preparation – In board exams, formula-based questions are common. In JEE/NEET, shortcut methods using equations save time.

3. Application-Based Learning – Physics equations apply in real-life phenomena like electric circuits, gravitational forces, optics, and nuclear energy.

Complete Physics Equation Mechanism Class 12 Formulas and Short Notes

We will divide the Physics Class 12 syllabus into chapters and provide important formulas + short notes under each.

1. Electrostatics

Important Formulas:

• Coulomb’s Law:

  F=14πϵ0⋅q1q2r2F = \frac{1}{4 \pi \epsilon_0} \cdot \frac{q_1 q_2}{r^2}F=4πϵ0​1​⋅r2q1​q2​​

• Electric Field:

  E=Fq=14πϵ0⋅Qr2E = \frac{F}{q} = \frac{1}{4 \pi \epsilon_0} \cdot \frac{Q}{r^2}E=qF​=4πϵ0​1​⋅r2Q​

• Electric Potential:

  V=14πϵ0⋅QrV = \frac{1}{4 \pi \epsilon_0} \cdot \frac{Q}{r}V=4πϵ0​1​⋅rQ​

• Capacitance:

  C=QVC = \frac{Q}{V}C=VQ​

• Energy Stored in Capacitor:

  U=12CV2U = \frac{1}{2}CV^2U=21​CV2

Short Notes:

• Like charges repel, unlike charges attract.

• Field lines never intersect.

• Dielectric increases capacitance.

2. Current Electricity

Important Formulas:

• Ohm’s Law:

  $$V=IR$$

• Resistance in Series:

  Req=R1+R2+R3+…R_{eq} = R_1 + R_2 + R_3 + \dotsReq​=R1​+R2​+R3​+…

• Resistance in Parallel:

  1Req=1R1+1R2+1R3+…\frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + \dotsReq​1​=R1​1​+R2​1​+R3​1​+…

• Drift Velocity:

  vd=InAev_d = \frac{I}{nAe}vd​=nAeI​

• Current Density:

  J=IAJ = \frac{I}{A}J=AI​

Short Notes:

• Resistance increases with temperature in metals.

• Superconductors have zero resistance.

• Kirchhoff’s Rules: Junction rule (∑I=0), Loop rule (∑V=0).

3. Magnetic Effects of Current & Magnetism

Important Formulas:

• Magnetic Field due to Current-Carrying Wire:

  B=μ0I2πrB = \frac{\mu_0 I}{2 \pi r}B=2πrμ0​I​

• Force on Moving Charge:

  $$F=q(v\times B)=qvB\sin \theta$$

• Force on Current-Carrying Conductor:

  $$F=BIL\sin \theta$$

• Torque on Current Loop:

  $$\tau =nBIA\sin \theta$$

• Magnetic Dipole Moment:

  $$M=IA$$

Short Notes:

• Right-hand thumb rule determines magnetic field direction.

• Magnetic susceptibility (χ) defines material response.

• Diamagnetic (χ<0), Paramagnetic (χ>0), Ferromagnetic (very high χ).

4. Electromagnetic Induction & Alternating Current

Important Formulas:

• Faraday’s Law:

  ε=−dΦBdt\varepsilon = -\frac{d\Phi_B}{dt}ε=−dtdΦB​​

• Self-Inductance:

  ε=−LdIdt\varepsilon = -L \frac{dI}{dt}ε=−LdtdI​

• RMS Value of Current:

  Irms=I02I_{rms} = \frac{I_0}{\sqrt{2}}Irms​=2​I0​​

• Power in AC Circuit:

  $$P=VI\cos \varphi$$

• Resonance Frequency:

  f=12πLCf = \frac{1}{2\pi\sqrt{LC}}f=2πLC​1​

Short Notes:

• Lenz’s Law: Induced EMF opposes the cause.

• In AC circuits, resistors, capacitors, and inductors combine to form impedance.

• Resonance in an RLC circuit gives maximum current.

5. Optics

Important Formulas:

• Lens Formula:

  1f=1v−1u\frac{1}{f} = \frac{1}{v} – \frac{1}{u}f1​=v1​−u1​

• Magnification:

  M=h′h=vuM = \frac{h’}{h} = \frac{v}{u}M=hh′​=uv​

• Mirror Equation:

  1f=1u+1v\frac{1}{f} = \frac{1}{u} + \frac{1}{v}f1​=u1​+v1​

• Snell’s Law:

  n1sin⁡i=n2sin⁡rn_1 \sin i = n_2 \sin rn1​sini=n2​sinr

• Interference (Young’s Double Slit):

  Δy=λDd\Delta y = \frac{\lambda D}{d}Δy=dλD​

Short Notes:

• Wave optics explains interference, diffraction, and polarization.

• Reflection: Angle of incidence = Angle of reflection.

• Refraction causes the bending of light.

6. Dual Nature of Radiation and Matter

Important Formulas:

• Photoelectric Equation:

  hν=hν0+12mv2h\nu = h\nu_0 + \frac{1}{2}mv^2hν=hν0​+21​mv2

• de Broglie Wavelength:

  λ=hp=hmv\lambda = \frac{h}{p} = \frac{h}{mv}λ=ph​=mvh​

Short Notes:

• Light behaves as both a particle and a wave.

• Einstein explained the photoelectric effect using photons.

• Work function (φ) is the minimum energy needed to eject electrons.

7. Atoms and Nuclei

Important Formulas:

• Radius of nth Orbit (Bohr Model):

  rn=n2h2ϵ0πme2Zr_n = \frac{n^2h^2\epsilon_0}{\pi m e^2 Z}rn​=πme2Zn2h2ϵ0​​

• Energy of nth Orbit:

  En=−13.6Z2n2 eVE_n = -\frac{13.6Z^2}{n^2} \, eVEn​=−n213.6Z2​eV

• Mass-Energy Relation:

  E=mc2E = mc^2E=mc2

• Radioactive Decay:

  N=N0e−λtN = N_0 e^{-\lambda t}N=N0​e−λt

Short Notes:

• The nucleus consists of protons and neutrons.

• The binding energy keeps the nucleus stable.

• Half-life (T½) = ln(2)/λ.

8. Semiconductor Electronics

Important Formulas:

• Conductivity:

  $$\sigma =nq\mu$$

• Resistance of Semiconductor:

  R=ρ⋅lAR = \rho \cdot \frac{l}{A}R=ρ⋅Al​

• Current in Diode:

  I=I0(eV/ηVT−1)I = I_0(e^{V/\eta V_T} – 1)I=I0​(eV/ηVT​−1)

Short Notes:

• Intrinsic semiconductors: pure Si, Ge.

• Doping creates p-type and n-type.

• Diodes are used in rectifiers, LEDs, and photodiodes.

Tips to Learn Physics Equations and Mechanisms

1. Use Mnemonics – Create short codes for remembering formulas.

2. Practice Derivations – Even if not required to write in exams, derivations clarify mechanisms.

3. Make Flashcards – Keep formula flashcards for last-minute revision.

4. Solve Previous Year Papers – It tells you which formulas are most important.

5. Understand Units – Dimensional analysis can help check correctness.

FAQs: Physics Equation Mechanism Class 12 Formulas

Q1. What is the best way to remember Class 12 Physics formulas?
Ans: The best way is regular practice, writing formulas daily, using flashcards, and understanding derivations rather than rote learning.

Q2. Are all formulas important for board exams?
Ans: Yes, every formula in the NCERT is important. However, extra focus should be on derivation-based and numerical-based formulas.

Q3. How many marks are formula-based questions in the Class 12 Physics board exam?
Ans: On average, 30–40% of the paper contains direct or indirect formula-based questions.

Q4. Can I skip derivations and just memorize formulas?
Ans: It is not recommended. Understanding derivations helps in application-based and tricky numerical problems.

Q5. Which chapters have the most formula-based numericals?
Ans: Electrostatics, Current Electricity, Optics, and Electromagnetic Induction are highly numerical-based.

Conclusion: Physics Equation Mechanism Class 12 Formulas

Physics is not only about memorization but also about understanding the mechanism behind equations. By practicing regularly, keeping Physics Equation Mechanism Class 12 Formulas and Short Notes handy, and focusing on conceptual clarity, you can excel in both board and competitive exams.

This complete set of formulas + short notes serves as a revision guide for Class 12 students. If you master these, you can solve almost any problem in the exam efficiently.

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