Important physics derivations for CBSE class 12 exam.

Believe me, if you just go through these derivations. theory and commit them to memory, nothing can stop you from scoring above 60 / 70 in the boards.

I will not tell you which among this exhaustive list of derivations is important or of high priority, so that you give equal attention and time to each and every one of them.

Here is the chapter-wise pdf file containing each of the below listed derivations. Use it as per convenience.

To See The Links Of PDFs Click Here

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Chapter 1 - Ch1.pdf

Chapter 2 - Ch2.pdf

Chapter 3 - Ch3.pdf

Chapter 4 - Ch4.pdf

Chapter 5 - Ch5.pdf

Chapter 6 - Ch6.pdf

Chapter 7 - Ch7.pdf

Chapter 8 - Ch8.pdf

Chapter 9 - Ch9.pdf

Chapter 10 - Ch10.pdf

Chapter 11 - Ch11.pdf

Chapter 12 - Ch12.pdf

Chapter 13 - Ch13.pdf

Chapter 14 - Ch14.pdf

Preview Of Some Given Links

Due credit must be given to the author of the book from where I could scan and upload the derivations, SL Arora. I do not own the rights to the source book of these derivations. No copyright infringement intended.

As you might have noticed, I have not given any derivation, or pdf file for Chapter 15 (Communication Systems) because CBSE generally doesn’t ask derivations from this lesson, nor are there derivations here worth learning in 12th..

But I am providing a chapter-wise marks weightage in the boards:

1. Chapters 1 & 2 - 8M
2. Chapter 3 - 7M
3. Chapters 4 & 5 - 8M
4. Chapters 6 & 7 - 8M
5. Chapter 8 - 3M
6. Chapters 9 and 10 - 14M
7. Chapter 11 - 4M
8. Chapters 12 and 13 - 6M
9. Chapter 14 - 7M
10. Chapter 15 - 5M

Wish you all the very best for your board exams..

Chapter 1 (Electric Charges and Fields)

1. Coulomb’s law of Electric Force
2. Coulomb’s law in vector form
3. Principle of superposition of electrostatic forces
4. Electric field (EF) due to a point charge
5. EF due to a system of point charges
6. EF at axial point of electric dipole
7. EF at equatorial point of electric dipole
8. Torque on a dipole in uniform EF
9. Gauss’s theorem
10. EF due to a uniformly charged infinite plane sheet
11. EF of 2 positively charged parallel plates
12. EF due to 2 oppositely charged parallel plates
13. EF due to uniformly charged thin spherical shell
14. EF of a line charge (from Coulomb’s law)
15. EF due to an infinitely long straight charged wire
16. Deduction of Coulomb’s law from Gauss’s theorem

Chapter 2 (Electrostatic Potential & Capacitance)

1. Electric Potential (EP) due to a point charge.
2. EP at an axial point of dipole
3. EP at an equatorial point of dipole
4. EP at any general point due to a dipole
5. EP due to a group of point charges
6. EP due to uniformly charged thin spherical shell
7. Relation between EF & EP
8. Potential Energy (PE) of system of 2 point charges
9. PE of a system of 3 point charges
10. PE of a system of N point charges
11. PE of a single charge
12. PE of system of 2 point charges in an external field
13. PE of a dipole placed in an uniform electric field
14. Parallel Plate Capacitor (Capacitance)
15. Capacitors in series & parallel
16. Energy stored in a capacitor
17. Energy stored in series combination of capacitors
18. Energy density of an EF
19. Reduced field inside a dielectric & dielectric constant
20. Electric susceptibility
21. Relation between electric susceptibility & dielectric constant
22. Capacitance of a parallel plate capacitor with a dielectric slab
23. Collecting action of a hollow sphere

Chapter 3 (Current Electricity)

1. Wheatstone Bridge (Working & Balanced condition)
2. Meter Bridge (Principle, Construction & Working )
3. Potentiometer (Principle, Construction)
4. Applications of a potentiometer:

• Comparison of emfs of 2 primary cells
• Internal resistance of a primary cell

5. Resistances in series & parallel

6. Relation between potential difference (V), internal resistance (r) and emf (E)

7. Cells in series and parallel

8. Condition for max current from (series & parallel) combination of cells

9. Power consumed by (series & parallel) combination of appliances

10. Mobility of charge carriers

11. Relation between (b/w) electric current (I) and mobility for conductors

12. Relaxation time and drift velocity

13. Relation b/w (I) and drift velocity

14. Deduction of Ohm’s law (from drift velocity)

15. Ohm’s law in vector form

Chapter 4 (Moving charges & Magnetism)

1. Biot-Savart’s law (statement and derivation of formula)
2. Magnetic Field (MF) due to a long straight current carrying conductor
3. MF at center of circular current loop.
4. MF along axis of circular current loop
5. Ampere’s circuital law (its proofs for straight current carrying conductor & straight conductor)
6. Calculation of MF inside a long straight solenoid
7. MF due to a toroidal solenoid
8. Moving coil galvanometer (MCG) (Principle, construction, theory and working)
9. Figure of merit and sensitivity (current & voltage) of a MCG
10. Conversion of MCG to Ammeter
11. Conversion of MCG to Voltmeter
12. Torque on current loop in uniform MF
13. Force between 2 parallel current carrying wires
14. Force on a current carrying conductor in MF
15. Cyclotron (Principle, construction, theory, working and expression for max KE of accelerated ions)
16. Work done by a magnetic force on a charged particle
17. Velocity selector

Chapter 5 (Magnetism & Matter)

1. MF of a bar magnet at an (axial & equatorial) point
2. Torque on magnetic dipole in a uniform MF
3. Potential energy of magnetic dipole
4. Current loop as magnetic dipole
5. Magnetic dipole moment of a revolving electron

Chapter 6 (Electromagnetic Induction)

1. Mutual Induction (its coefficient and emf in terms of coefficient and rate of change of current w.r.t time)
2. Mutual induction of 2 long solenoids
3. Self Induction (its coefficient and emf in terms of coefficient and rate of change of current w.r.t time)
4. Self inductance of a long solenoid
5. Different methods of generating emf (and the respective emf expressions)
6. Motional emf from Faraday’s law : Induced emf by change of area of coil linked with MF
7. Motional emf from Lorentz force , Current induced in loop, power delivered by external force and power dissipated as Joule loss

Chapter 7 (Alternating Current)

1. A.C Generator (Principle, construction, working and expression for induced emf)
2. Transformer (Principle, construction, working and theory)
3. Mathematical treatment of LC oscillations
4. Conservation of energy in LC oscillations
5. Mechanical analogy for LC oscillations
6. Power in A.C circuit
7. Average power associated with (resistor, inductor and capacitor)
8. Series LCR circuit (phasor diagrams, expression for impedance , resonance condition)
9. Sharpness of resonance : Q-Factor
10. Expression for Q-Factor
11. AC circuit containing resistor only (and phasor diagram)
12. AC circuit containing inductor only (and phasor diagram), phase relation b/w emf and current, inductive reactance
13. AC circuit containing capacitor only (and phasor diagram), phase relation b/w emf and current, capacitive reactance
14. Average value of AC over 1 complete cycle
15. Relation b/w avg and peak values of AC
16. Relation b/w effective and peak values of AC
17. Relation b/w rms and peak values of alternating emf

Chapter 8 (Electromagnetic Waves)

1. Maxwell’s modification of Ampere’s law
2. Consistency of modified Ampere’s law

Chapter 9 (Ray optics & optical instruments)

1. Cassegrain reflecting telescope (with diagram, magnification for final image formed at (infinity, least distance of distinct vision))
2. Astronomical telescope : When final image is formed at (infinity (normal adjustment), least distance of distinct vision) -working, diagrams and magnifying powers in each case
3. Compound microscope : When final image is formed at (infinity , least distance of distinct vision) - working, diagrams and magnifying powers in each case
4. Simple microscope : When final image is formed at (infinity , least distance of distinct vision) -working, diagrams and magnifying powers in each case
5. Formation of image by spherical lenses
6. Thin lens formula for a convex lens when it forms a (real & virtual) image
7. Thin lens formula for a concave lens
8. Linear magnification produced by a lens (in terms of u & f ; v & f)
9. Lens maker’s formula for a double convex lens , double concave lens
10. Refraction at convex spherical surface

• When object lies in rarer medium & image formed is real
• When object lies in rarer medium & image formed is virtual
• When object lies in denser medium & image formed is real
• When object lies in denser medium & image formed is virtual

11. Refraction at concave spherical surface

• When object lies in rarer medium
• When object lies in denser medium

12. Derivation of mirror formula for a concave mirror when it forms a (real & virtual) image

13. Derivation of mirror formula for a convex mirror

14. Linear magnification produced by mirrors (in terms of u & f ; v & f)

15. Refraction through a rectangular glass slab

16. ^^ and expression for lateral displacement

17, Equivalent focal length and power of 2 thin lenses in contact.

Chapter 10 (Wave Optics)

1. Laws of reflection on basis of Huygen’s wave theory
2. Laws of refraction on basis of Huygen’s wave theory
3. Refraction at a rarer medium
4. Refraction of a plane wavefront through a prism, convex lens and a concave mirror
5. Expression for intensity at any point in interference pattern ; and the corresponding conditions for (constructive & destructive) interference
6. Expression for fringe width in Young’s double slit experiment (YDSE) ; and formulae for positions of (bright & dark) fringes
7. Expression for ratio of intensities at maxima and minima in an interference pattern
8. Diffraction at a single slit - Central maximum, calculation of path difference, positions of minima, positions of secondary maxima, intensity distribution curve
9. (Angular & linear) width of central maximum, linear width of a secondary maximum
10. Fresnel’s distance & Fresnel’s zone
11. Resolving power of a microscope and telescope
12. Doppler effect - expression for apparent frequency of light, (blue & red) shifts

Chapter 11 (Dual nature of radiation and matter)

1. Determination of Planck’s constant and work function from graph of stopping potential vs frequency of incident radiation for a photosensitive material

Chapter 12 (Atoms)

1. Distance of closest approach in Rutherford’s experiment, and the formula for radius of nucleus which is thus derived from it
2. Bohr’s quantization condition of angular momentum
3. Bohr’s theory of hydrogen atom - formulae for radii of permitted orbits, velocity of electrons in those orbits and energy of electron in those orbits
4. Spectral series of hydrogen atom

Chapter 13 (Nuclei)

1. Formula for nuclear density in terms of radius of a nucleus
2. Expression for binding energy
3. Radioactive decay law
4. Relation b/w half life & decay constant
5. Relation b/w mean life & decay constant
6. Decay rate / activity of a radioactive sample

Chapter 14 (Semiconductor electronics)

1. Truth table, logic symbols and waveform examples for NOT, AND, OR, NAND and NOR gates
2. npn transistor as a common emitter (CE) amplifier ; (current,voltage and power) gains of a CE amplifier
3. Amplifier theory
4. Transistor as a switch - 3 states of a transistor (cutoff, active and saturation) , switching action of a transistor
5. Actions of (npn & pnp) transistors
6. Current gains in a transistor (α & β) and the relation b/w them
7. CE characteristics (input & output and their theory)
8. Solar cell (construction, working, diagram, and V-I characteristic)
9. Light emitting diode (LED) - (construction, working, diagram, and I-V characteristic)
10. Photodiode (construction, working, diagrams and I-V characteristic)
11. Cause of reverse breakdown of a junction diode - (Zener & avalanche) breakdowns ; their causes in brief and V-I characteristics in both cases
12. Zener diode - construction, working, diagram
13. Zener diode as a voltage regulator - working, diagram and graph b/w (input & output) voltages
14. Junction diode as a (half-wave & full-wave) rectifier - working, diagrams and waveform graphs
15. Working of a p-n junction in both types of (forward & reverse) biasing - diagrams and brief theory
16. V-I characterisics of a p-n junction diode - forward-bias & reverse bias characteristic graphs and their brief theory
17. p-n junction - working in brief, diagram