Physics Theory Notes

Scientific Method & Scope of Physics

Physics: The fundamental science that studies matter, energy, and their interactions.

Physical Quantities & SI Units

Physical Quantity: A property of a material or system that can be measured and expressed numerically.

Dimensions & Dimensional Analysis

Dimension: A qualitative description of a physical quantity in terms of fundamental base quantities (mass, length, time, etc.).

Measuring Instruments & Errors

Systematic Error: An error that is constant or changes in a predictable way under repeated measurements.

Vectors & Resolution

Scalar Quantity: A physical quantity that has only magnitude (size) and no direction.

Graphs & Data Interpretation

Linear Relationship (y = mx + c): A relationship where a constant change in the independent variable produces a constant change in the…

Linear Motion & Projectile Motion

Displacement (s): The straight-line distance from the starting point to the final point, with direction.

Forces & Newton’s Laws

Force: A push or pull that can change an object’s state of motion or shape.

Moments & Equilibrium

Moment of a Force (Torque): The turning effect of a force about a pivot.

Work, Energy & Power

Work (W): The product of force and displacement in the direction of the force.

Circular Motion

Angular Displacement (θ): The angle swept out by a radius vector as an object moves along a circular path.

Fluid Statics

Fluid Pressure: Pressure is defined as force per unit area acting perpendicular to a surface.

Fluid Dynamics

Fluid Flow and Continuity Equation: The principle that for an incompressible fluid flowing through a pipe of varying cross-sectional area,…

Fluids in Motion (Hydrodynamics)

Steady (Laminar) Flow: Flow where every particle passing a given point follows the same path, with velocity constant at that point over…

Simple Harmonic Motion

Simple Harmonic Motion (SHM): A periodic motion where the restoring force is directly proportional to the displacement from equilibrium and…

Wave Motion

Progressive Wave: A disturbance that transfers energy from one point to another without the net transfer of the medium itself.

Wave Phenomena (Reflection, Refraction, Diffraction, Interference)

Reflection: The bouncing back of a wave when it encounters a boundary between two media.

Stationary Waves & Resonance

Stationary (Standing) Wave: A wave pattern formed by the superposition of two identical waves travelling in opposite directions, resulting…

Sound & Doppler Effect

Sound as a Longitudinal Wave: Sound is a mechanical wave that propagates through a medium (solid, liquid, or gas) via compressions and…

EM Waves & LASER

Electromagnetic (EM) Wave: A transverse wave consisting of mutually perpendicular oscillating electric (E) and magnetic (B) fields,…

Temperature & Thermometers

Temperature: A measure of the average kinetic energy of the particles in a substance.

Thermal Expansion

Linear Expansion: The increase in length of a solid when its temperature rises.

Gas Laws & Kinetic Theory

Ideal Gas: A hypothetical gas whose molecules occupy negligible volume and have no intermolecular forces.

Calorimetry & Specific Heat

Heat Capacity (C): The amount of heat energy required to raise the temperature of an entire object by 1 K (or 1 °C).

Latent Heat & Phase Change

Latent Heat: The thermal energy absorbed or released by a substance during a phase change at constant temperature.

Heat Transfer

Conduction: The transfer of thermal energy through a material without bulk motion of the material itself.

Humidity & Vapour Pressure

Vapour Pressure: The partial pressure exerted by water vapour molecules in a gas mixture.

Thermodynamic Processes

Thermodynamic Process: A change in the state of a system (defined by pressure, volume, and temperature) from an initial equilibrium state…

Newton’s Law of Gravitation

Gravitational Force: A fundamental attractive force that exists between any two objects with mass.

Gravitational Field & Field Intensity

Gravitational Field: A region of space where a mass experiences a gravitational force.

Gravitational Potential & Potential Energy

Gravitational Potential (V): The work done per unit mass in bringing a small test mass from infinity to a point in the gravitational field.

Orbital Motion & Satellites

Earth's Gravitational Field Intensity: The gravitational field intensity at a point on or outside the Earth is the gravitational force per…

Escape Velocity & Energy of Orbits

Escape Velocity: The minimum speed required for an object to escape a planet's gravitational field without further propulsion.

Electric Charge & Coulomb’s Law

Electric Charge (Q): A fundamental property of matter that causes it to experience a force in an electric field.

Electric Field & Electric Field Intensity

Electrostatic Field and Force: An electrostatic field (also called electric field) is a region of space around a charged object where…

Electric Potential & Potential Energy

The electrostatic potential at a point in an electric field is defined as the work done in bringing a unit positive charge from infinity to…

Electric Flux & Gauss’s Law

Electric Flux Model: Electric flux is a measure of the number of electric field lines passing through a given area, representing the flow…

Capacitors & Capacitance

Capacitor: A device that stores electrical energy in an electric field.

Electric Current & Charge Flow

Electric Current (I): The rate of flow of electric charge through a cross-section of a conductor.

Ohm’s Law, Resistance & Resistivity

Ohm’s Law: At constant temperature, the current through a conductor is directly proportional to the potential difference across it.

EMF, Internal Resistance & Cells

Electromotive Force (EMF, ε): The total energy supplied per unit charge by a source (cell or generator) when no current is drawn.

Series & Parallel Circuits

Series Circuit: A circuit where components are connected end-to-end, forming a single path for current.

Kirchhoff’s Laws

Kirchhoff’s Current Law (KCL): The algebraic sum of currents entering a junction equals the algebraic sum of currents leaving that junction.

Wheatstone Bridge & Meter Bridge

Wheatstone Bridge Principle: A circuit used to measure an unknown resistance by balancing two ratio arms.

Potentiometer

Potentiometer: A device used to measure potential difference (voltage) without drawing any current from the source.

Magnetic Fields & Magnetic Force

Magnetic Field (B): A region of space where a moving charge or a magnetic material experiences a force.

Magnetic Fields of Conductors & Solenoids

Magnetic Field due to a Long Straight Conductor: A current-carrying straight wire produces a circular magnetic field around it.

Electromagnetic Induction

Magnetic Flux (Φ): The product of the magnetic flux density and the area perpendicular to the field.

Alternating Current & RMS

Alternating Current (AC): A current that periodically reverses direction, with its magnitude varying sinusoidally with time.

Inductive & Capacitive Reactance

Reactance (X): The opposition to alternating current (AC) offered by an inductor or capacitor, measured in ohms (Ω).

Transformers

Transformer: A static electrical device that transfers electrical energy between two or more circuits through electromagnetic induction,…

Generators & Motors

Electromagnetic Induction (Generator Principle): The production of an EMF in a conductor when the magnetic flux through it changes.

Semiconductors & p–n Junctions

Energy Bands in Solids: In a solid, discrete atomic energy levels broaden into bands: the valence band (filled with electrons) and the…

Diodes & Rectification

Semiconductor Diode: A two-terminal device that allows current to flow primarily in one direction.

Zener Diodes & Regulation

Zener Diode: A diode designed to operate in the reverse breakdown region at a precise, stable voltage.

Bipolar Junction Transistors (BJT)

Bipolar Junction Transistor (BJT): A three-terminal semiconductor device that uses both electron and hole charge carriers to amplify or…

Field Effect Transistors (FET/JFET/MOSFET)

Field Effect Transistor (FET): A voltage-controlled semiconductor device where output current is controlled by an electric field applied…

Operational Amplifiers (Op‑Amps)

Operational Amplifier (Op‑Amp): A high‑gain DC-coupled differential voltage amplifier with two inputs and one output.

Logic Gates & Boolean Algebra

Logic Gate: A digital electronic circuit that performs a Boolean function on one or more binary inputs to produce a single binary output.

Flip‑Flops & Sequential Logic

Sequential Logic Circuit: A circuit whose output depends on both current inputs and the past sequence of inputs (i.e., it has memory).

Stress, Strain & Elasticity

Elasticity: The property of a material to regain its original shape and size after the deforming force is removed.

Young’s Modulus & Elastic Potential Energy

Stress (σ): The restoring force per unit cross-sectional area within a deformed material.

Viscosity & Fluid Resistance

Viscosity: A measure of a fluid’s internal resistance to flow.

Surface Tension & Capillarity

Surface Tension (γ): The force per unit length acting along the surface of a liquid, perpendicular to any line drawn in the surface,…

Pressure in Fluids, Upthrust & Archimedes’ Principle

Fluid Pressure: The force exerted per unit area by a fluid at rest, acting perpendicular to any surface in contact with it.

Fluid Dynamics (Bernoulli, Continuity, Flow Rate)

Steady (Laminar) Flow: Flow where every fluid particle passing a given point follows the same path, with velocity constant in time at any…