1. Basic Concepts of Physics

Physics is the branch of science that studies matter, energy, motion and the interactions between them.

• Mechanics: Study of motion, force and energy.
• Thermodynamics: Study of heat, temperature and energy transfer.
• Optics: Study of light.
• Acoustics: Study of sound.
• Electromagnetism: Study of electricity and magnetism.
• Modern Physics: Study of atoms, nuclei, quantum phenomena and relativity.

2. Units and Measurement

Measurement is the comparison of a physical quantity with a standard unit.

• 1 kilometre = 1000 metres.
• 1 hour = 3600 seconds.
• Density = Mass ÷ Volume.
• Speed = Distance ÷ Time.

3. Motion

Motion is the change in the position of an object with respect to a reference point over time.

• Distance: Total path travelled by an object.
• Displacement: Shortest directed distance between initial and final positions.
• Speed: Rate of change of distance.
• Velocity: Rate of change of displacement.
• Acceleration: Rate of change of velocity.

4. Force and Newton’s Laws of Motion

Force is a push or pull that can change the state of motion or shape of an object.

• First Law: An object remains at rest or in uniform straight-line motion unless acted upon by an external unbalanced force.
• Second Law: Force is equal to the rate of change of momentum. For constant mass, F = ma.
• Third Law: Every action has an equal and opposite reaction.

Momentum: p = mv

Impulse: Impulse = Force × Time interval

5. Work, Energy and Power

• Work: Work is done when a force causes displacement in the direction of the force.
• Energy: Capacity to do work.
• Power: Rate of doing work.
• Kinetic Energy: Energy possessed due to motion: KE = ½mv².
• Potential Energy: Energy possessed due to position or configuration: PE = mgh near Earth’s surface.

Law of Conservation of Energy: Energy can neither be created nor destroyed; it can only be transformed from one form to another.

6. Gravitation

Gravitation is the force of attraction between any two masses.

• Newton’s law of gravitation: F = Gm₁m₂/r².
• The acceleration due to gravity on Earth is approximately 9.8 m/s².
• Weight = Mass × Acceleration due to gravity.
• Mass remains constant, while weight may change with gravity.
• Escape velocity from Earth is approximately 11.2 km/s.
• Artificial satellites remain in orbit due to gravitational force.

7. Properties of Matter

• Mass: Amount of matter in an object.
• Volume: Space occupied by an object.
• Density: Mass per unit volume.
• Pressure: Force acting per unit area.
• Elasticity: Ability of a material to regain its original shape after removal of deforming force.
• Viscosity: Resistance offered by a fluid to flow.
• Surface tension: Tendency of a liquid surface to behave like a stretched elastic membrane.

Pascal’s law: Pressure applied to an enclosed fluid is transmitted equally in all directions.

Archimedes’ principle: An immersed object experiences an upward buoyant force equal to the weight of the fluid displaced by it.

8. Heat and Temperature

• Heat: Energy transferred due to a temperature difference.
• Temperature: Measure of the degree of hotness or coldness of a body.
• Heat is measured in joules in the SI system.
• Temperature is measured in kelvin in the SI system.
• Heat transfer takes place by conduction, convection and radiation.
• Metals are generally good conductors of heat.
• Black and rough surfaces are good absorbers and emitters of radiation.

9. Thermodynamics

Thermodynamics deals with heat, work, temperature and energy transformations.

• Zeroth Law: If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other.
• First Law: Energy is conserved in a thermodynamic process.
• Second Law: Natural heat transfer occurs spontaneously from a hotter body to a colder body.
• Third Law: The entropy of a perfect crystal approaches zero as temperature approaches absolute zero.

10. Waves and Sound

• A wave transfers energy from one place to another without a net transfer of matter.
• Frequency: Number of oscillations per second; unit is hertz.
• Wavelength: Distance between two successive points in the same phase.
• Amplitude: Maximum displacement from the mean position.
• Time period: Time required for one complete oscillation.
• Sound requires a medium for propagation and cannot travel through a vacuum.
• Human beings generally hear frequencies from 20 Hz to 20,000 Hz.
• Ultrasonic waves have frequencies above 20,000 Hz.
• Infrasonic waves have frequencies below 20 Hz.

Wave equation: Wave speed = Frequency × Wavelength.

Echo: Reflection of sound heard separately from the original sound.

11. Light and Optics

• Light is a form of electromagnetic radiation.
• Light can travel through a vacuum.
• Speed of light in vacuum is approximately 3 × 10⁸ m/s.
• Reflection: Bouncing back of light from a surface.
• Refraction: Bending of light when it passes from one medium to another.
• Dispersion: Splitting of white light into its component colours.
• Diffraction: Bending or spreading of waves around obstacles and apertures.
• Interference: Redistribution of intensity due to superposition of waves.

12. Electricity

• Electric charge: A fundamental property responsible for electrical interaction.
• Electric current: Rate of flow of electric charge.
• Potential difference: Work done per unit charge.
• Resistance: Opposition offered to the flow of electric current.
• Ohm’s Law: V = IR, when physical conditions remain constant.
• Electric power: P = VI = I²R = V²/R.
• Electric energy: Energy consumed by an electrical device over time.

Series circuit: The same current flows through all components.

Parallel circuit: The potential difference across each branch is the same.

13. Magnetism

• A magnet has two poles: north and south.
• Like poles repel each other, while unlike poles attract each other.
• Magnetic field lines emerge from the north pole and enter the south pole outside a magnet.
• Electric current produces a magnetic field.
• An electromagnet is a temporary magnet produced by passing current through a coil.
• An electric motor converts electrical energy into mechanical energy.
• An electric generator converts mechanical energy into electrical energy.
• Electromagnetic induction was discovered by Michael Faraday.

14. Modern Physics

• Atom: Basic unit of an element consisting of a nucleus and electrons.
• Electron: Negatively charged subatomic particle.
• Proton: Positively charged particle found in the nucleus.
• Neutron: Electrically neutral particle found in the nucleus.
• Isotopes: Atoms of the same element with the same atomic number but different mass numbers.
• Radioactivity: Spontaneous emission of radiation from unstable atomic nuclei.
• Alpha particles: Helium nuclei.
• Beta particles: High-speed electrons or positrons.
• Gamma rays: High-energy electromagnetic radiation.
• Photoelectric effect: Emission of electrons from a material when suitable electromagnetic radiation falls on it.

Mass-energy relation: E = mc².

15. Semiconductors and Electronics

• Semiconductors have electrical conductivity between conductors and insulators.
• Silicon and germanium are commonly used semiconductor materials.
• Diode: A device that generally allows current to flow mainly in one direction.
• LED: Light-emitting diode that emits light when current passes through it under suitable conditions.
• Transistor: A semiconductor device used for amplification and switching.
• Solar cell: Converts light energy into electrical energy.
• Integrated circuit: A set of electronic components fabricated on a small semiconductor chip.
• Logic gates: Digital circuits that perform logical operations.

16. Quick Revision Facts