Class 12 Physics Important Derivations for CBSE Boards 2027 (Chapter-wise List)

Derivations are a reliable source of marks in Class 12 Physics. Here's a chapter-wise list of the standard NCERT derivations. CBSE has removed some topics in recent syllabus changes, so tick these against the current syllabus on cbseacademic.nic.in.

Electrostatics

• Electric field of a dipole on the axial and equatorial lines
• Torque on a dipole in a uniform field
• Field using Gauss's law: infinitely long straight wire, infinite plane sheet, thin spherical shell
• Potential due to a dipole
• Capacitance of a parallel plate capacitor, with and without a dielectric slab
• Energy stored in a capacitor; capacitors in series and parallel

Current Electricity

• Relation between current and drift velocity (I = neAv_d)
• Deriving Ohm's law from drift velocity
• Wheatstone bridge balance condition

Magnetism and EMI

• Magnetic field on the axis of a circular loop (Biot–Savart law)
• Field of a long straight wire and of a solenoid (Ampère's law)
• Force between two parallel current-carrying conductors
• Torque on a current loop in a magnetic field
• Motional emf; self-inductance of a long solenoid; mutual inductance of two coaxial solenoids

Alternating Current

• Impedance of a series LCR circuit, and the resonance condition
• Average power in an AC circuit; power factor

Optics

• Refraction at a spherical surface; lens maker's formula; thin lens formula
• Angle of minimum deviation for a prism
• Magnifying power of a compound microscope and an astronomical telescope
• Laws of reflection and refraction using Huygens' principle
• Fringe width in Young's double-slit experiment

Atoms

• Radius and energy of the electron in Bohr's model of hydrogen

How to learn them

1. Understand the physical setup and draw the diagram.
2. Write the starting law (Coulomb, Gauss, Biot–Savart, Ampère).
3. Practise each derivation in full twice: once with the book, once without.
4. Revise one or two a day in the last month.