Derivations in physics are very important for CBSE class 12 board exams. Practicing them is necessary for getting good marks.

It’s going to be a long answer.

The following derivations are the most important from examination point of view. I am going to discuss them chapterwise. Try to learn the basic concept and application of these derivations instead of just mugging them up.

Here you go…

- Electrostatics:
- Coulomb’s law
- Electric field intensity of a dipole at axial and equatorial positions
- Electric field intensity at any point due to an ideal dipole
- Force and torque acting on a dipole in an external uniform electric field
- Work done to rotate a dipole in an external uniform electric field
- Gauss’ theorem (verification and application)
- Electric field intensity due to a thin uniformly charged plane sheet
- Electric field intensity due to an uniformly charged spherical shell
- Electric potential at a point due to a point charge
- Capacitance of a parallel plate capacitor
- Capacitance of a single and concentric sphere
- Energy stored in a capacitor
- Effect of dielectric medium on the capacitance of a parallel plate capacitor
- Series and parallel combination of capacitor

- Current electricity
- Ohm’s law and it’s derivation
- Drift velocity of free electrons and it’s relation with current
- Series and parallel combination of resistors
- Kirchhoff’s law and simple application
- Learn formulas and practice numerical of the following
- Meterbridge, Ammeter, Voltmeter, Potentiometer

- Magnetic effects of current and electricity
- Biot-Savart’s law
- Magnetic field intensity due to a straight current carrying conductor of finite length
- Magnetic field intensity due to a circular loop of current carrying conductor
- Magnetic field at any point on the axis of a circular loop and coil
- Ampere’s cicuital law and it’s applications
- Magnetic field due to an infinitely long straight current carrying conductor
- Magnetic field intensity at any point inside a straight infinitely long solenoid and toroid

- Lorentz law and it’s properties
- Motion of a charged particle in a magnetic field when the velocity is perpendicular to the magnetic field
- Motion of a charged particle in a magnetic field when the velocity is not perpendicular to the magnetic field
- Cyclotron (principal + construction + working)
- Force on a current carrying conductor in an uniform magnetic field
- Force and torque acting on a current carrying loop in an uniform magnetic field
- Moving coil galvanometer (principle + construction + working)
- Force between parallel current carrying conductors

- Magnetism and matter
- Magnetic field due to a magnetic dipole at axial line and equatorial line
- Force and torque acting on a dipole moment in an external uniform electric field
- Work done in rotating a magnetic dipole in an uniform magnetic field
- Terrestrial magnetism
- Dia, para and ferro magnetic substances

- Electromagnetic induction
- Faraday’s experiment
- Motional EMF or induced EMF
- Self inductance and work done
- Mutual inductance

- Alternating current
- A.C. Generator (Diagram, Principle, Construction and working). Derive the expression for induced emf and current
- Transformer ( Principle, Construction, Working and Theory).
- How is current affected in transformer?
- What are energy loss in transformers, how can they be reduced?

- Mathematical treatment of L-C oscillation
- Conservation of energy in L-C oscillation
- Define power for an A.C. circuit. Derive an expression for the average of a series L-C-R circuit connected to an A.C. source. Discuss the various special cases
- Impedance, Reactance and average power in series L-C-R, L-R, L-C or C-R circuit
- Derive an expression for the impedance of a series LCR circuit using phasor diagram
- Resonance condition of a series LCR circuit. Calculate is resonant frequency
- Sharpness of resonance in a series resonant circuit. Find expression for Q-factor of circuit
- A.C. circuit containing
- Inductor
- Resistor
- Capacitor
- Draw phasor diagram, graph of E and V versus wt

- Average value of A.C. over one complete cycle
- Relation between the rms value and peak value of an alternating current
- Relation between the effective and peak value of an alternating current
- Relation between average value and peak value of an alternating current

- Electromagnetic waves
- Derivation of displacement current
- Characteristics and properties of EM waves
- Electromagnetic spectrum

- Ray optics and optical instruments
- Reflection from spherical mirror and find relation between f and r
- Mirror formula using concave and convex mirror
- Total internal reflection
- Refraction through spherical surfaces
- Lens maker’s formula
- Refraction through a glass prism and minimum angle of deviation
- Scattering of light
- Optical instruments

- Wave optics
- Expression for the intensity at any point on the observation screen in Young’s double slit experiment and find the condition for constructive and destructive interference
- Expression for fringe width in Young’s double slit experiment. How can the wavelength of monochromatic light be found by this experiment?
- Diffraction using single slit
- Deduce expression for
- Angular width of Central maximum
- Linear width of Central maximum
- Linear width of secondary maximum