XII.XV Communication Systems

Out of all the names who contributed in development of communication systems, one name that makes every Indian Student takes pride in is Sir Jagadish Chandra Bose. A crater on the moon has been named in his honour. Bose made his inventions public in order to allow others to further develop his research.

XII.XIV Semiconductor Electronics: Material, Devices And Simple Circuits

The energy band structure in solids may be classified in four broad types as shown in figure. The gap between the top of valence band and bottom of conduction band is called the energy gap.

In a pure semiconductor (intrinsic semiconductor), number of conduction electrons and holes is equal.

Semiconductor with an impurity doped into it is called extrinsic semiconductor

• n-type semiconductor (doped with pentavalent)
• p-type semiconductor (doped with trivalent)

The conductivity of a semiconductor increases as the temperature is increased, as more electrons cross the energy gap and number of electron holes pair increases.

XII.XIII Nuclei

Radioactivity is a nuclear phenomenon in which an unstable nucleus undergoes a decay:

• alpha decay in which a helium nucleus is emitted
• beta decay in which electrons or positrons are emitted
• gamma decay in which high energy photons are emitted

XII.XII Atoms

We did discuss about Thomson's Model of the Atom and Rutherford's model in Class IX. Go to this page if you want to read it again.

XII.X Wave Optics

XII.IX Ray Optics And Optical Instruments

XII.VIII Electromagnetic Waves

Maxwell's equation is a collection of four fundamental equations;

• Gauss' law of electricity
• Gauss' law of magnetism
• Faraday's law
• Ampere-Maxwell law

XII.VII Alternating Current

XII.VI Electromagnetic Induction

XII.V Magnetism And Matter

XII.IV Moving Charges And Magnetism

XII.III Current Electricity

XII.II Electrostatic Potential And Capacitance

Electrostatics of conductors;

• Inside a conductor, electrostatic field is zero
• At the surface of a conductor, electrostatic field must be normal to the surface at every point
• The interior of a conductor can have no excess charge in the static situation, any excess charge must reside at the surface
• Electrostatic Shielding: Any cavity in a conductor remains shielded from outside electric influence; the field inside the cavity is always zero

XI.VIII Gravitation

XI.VII System of Particles And Rotational Motion

XI.VI Work, Energy And Power

XI.V Laws Of Motion

XI.IV Motion In A Plane

XI.III Motion In A Straight Line

XI.II Units And Measurements

Multiples and Sub-multiples:

nano	micro	milli	centi	deci	deca	hecto	kilo	Mega	Giga	Tera
-9	-6	-3	-2	-1	1	2	3	4	5	6

Some Important Constants: The values of these constants are generally given in question papers. It is important to know their application, which we discuss in different chapters.

• Constant of gravitation, G = 6.67 x 10^-11 Nm²/kg²
• Speed of light in vacuum, c = 2.99 x 10⁸ m/s
• Avagadro constant, N = 6.022 x 10²³ mol^-1
• Gas constant, R = 8.314 JK^-1mol^-1
• Boltzmann constant, k = 1.38 x 10^-23 J/K = 8.614 x 10^-5eV/K
• Stefan-Boltzmann constant, σ = 5.67 x 10 ^-8 Wm^-2K^-4
• Wein's displacement law constant, b = 2.89 x 10^-3 mK
• Charge of proton, e = 1.6 x 10^-19 C
• Mass of electron, m_e = 9.1 x 10^-31 kg = 5.48 x 10^-3 u
• Mass of neutron, m_n = 1.67 x 10^-27 kg
• Permeability of vacuum, μ₀ = 4 π x 10^-27 Tm/A 
• Permittivity of vacuum, ε₀ = 8.854 x 10^-12 Wb A^-1 m^-1
• Faraday constant, F = 96485.3
• Planck constant, h = 6.626 x 10^-34 J s = 4.1357 x 10^-34 eV s
• Rydberg constant, R = 1.097 x 10^-7 m^-1
• Ground state energy of hydrogen atom = 13.6 eV
• Bohr radius, a₀ = 5.29 x 10^-11 m
• Electron-charge to mass ratio, e/m_e = 1.759 x 10^-11 c/kg

Some more constants

• Mechanical equivalent of heat, J = 4186  J/cal
• Standard atmospheric pressure, 1 atm = 1.013 x 10⁵ Pa
• Absolute zero, 0 K = 237.15 ° C
• Electron volt, 1eV = 1.602 x 10^-27J
• Unified Atomic mass unit, 1u = 1.661 x 10^-27 kg
• Electron rest energy, m_ec² = 1.661 x 10^-27 kg
• Energy equivalent of 1 atomic mass unit = 931.5 MeV
• Volume of ideal gas (0 °C, 1 atm), V = 22.4 L
• Acceleration due to gravity, g = 9.78 m/s²

Greek Alphabets:

alpha Α α beta Β β gamma Γ γ delta Δ δ epsilon Ε ε zeta Ζ ζ eta Η η theta Θ θ

iota Ι ι kappa Κ κ lambda Λ λ mu Μ μ nu Ν ν xi Ξ ξ omicron Ο ο pi Π π

rho Ρ ρ sigma Σ σ/ς tau Τ τ upsilon Υ υ phi Φ φ chi Χ χ psi Ψ ψ omega Ω ω

SI Units: Many of the units are named on the names of scientists

Fundamental quantities;

• Length: meter (m)
• Mass: kilograms (kg)
• Time: seconds (s)
• Charge: coulomb (C)
• Luminous intensity: candela (Cd)
• Temperature: kelvin (K)

Derived quantities;

• Current: ampere (A)
• Force: newton (N)
• Work/Energy: joule (J)
• Power: watt (W)
• Potential: volt (V)
• Frequency: hertz (Hz)
• Resistance: ohm (Ω)
• Magnetic flux: weber (Wb)
• Inductance: henry (H)
• Capacitance: farad (F)

Mathematical Formulas: These important formulas should be known for the subject

• Quadratic formula; ax² + bx + c = 0 has solutions x = (-b ± √D)/2a, where D = √(b² - 4ac)
• Binomial Theorem; (1 + x)ⁿ  = 1 + nx +.. if  x<<1
• Product of vectors; 
• Trigonometric Identities;
• Derivatives and Integrals;
• Cramer's rule;

XII.I Electrical Charges and Fields

Positive charge : fur, glass rod
Negative charge: wool, silk, plastic rod

XI.I Physical World

Physics (Greek:natural things) aims to analyze and understand the natural phenomenon of the universe.