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General Physics

General Science Physics Competitive Exams

Physics deals with matter, motion, force, energy, heat, sound, light, magnetism, electricity, and the working principles of common scientific instruments and devices. In competitive examinations, Physics questions usually test basic concepts, definitions, laws, examples, units, practical applications, and day-to-day observations.

What is Physics?

Physics is the branch of science that studies nature and natural phenomena. It explains how objects move, why bodies fall, how heat flows, how sound travels, how light reflects and refracts, how magnets behave, and how electricity is produced and used.

Physics builds the foundation for understanding machines, instruments, household appliances, transport, communication systems, weather instruments, optical devices, electrical circuits, and safety devices. For exams, the focus is on clear understanding rather than lengthy numerical calculations.

Quick idea: Physics explains the rules behind common experiences such as floating of ships, working of pressure cookers, formation of images in mirrors, ringing of bells, working of telephones, and protection from lightning.
Area What It Covers Exam Focus
Matter and Mechanics States of matter, mass, weight, volume, density, pressure, motion, force. Definitions, laws, examples, units.
Heat and Sound Effects of heat, temperature, latent heat, heat transfer, sound waves. Conceptual differences and applications.
Light and Optics Reflection, refraction, mirrors, lenses, human eye, optical instruments. Image formation and uses.
Magnetism and Electricity Magnets, Earth as magnet, static and current electricity, Ohm’s Law. Properties, circuits, effects of current.
Working Principles Pendulum, pulleys, siphon, levers, pumps, hydrometer, compass, fuse. Principle and practical use.

“Physics is the science that explains the working of the world around us.”

Science Tip
Key points
  • Understand matter, mass, weight, density, and pressure.
  • Learn motion, velocity, acceleration, force, and momentum.
  • Know Newton’s Laws and basic gravitation.
  • Revise heat, temperature, latent heat, and heat transfer.
  • Study sound, light, mirrors, lenses, and human eye.
  • Understand magnets, electricity, circuits, cells, and fuses.
  • Learn working principles of common instruments and devices.
motion force heat sound light electricity magnetism

Major Topics Covered in Physics

Physics is a wide chapter. It is useful to divide it into matter, mechanics, heat, waves, optics, magnetism, electricity, and practical devices.

Matter and Fluids

Basic physical properties and behaviour of substances.

  • States of matter
  • Mass and weight
  • Volume and density
  • Specific gravity
  • Archimedes’ principle
  • Pressure and barometer
Motion and Force

Study of movement and causes of movement.

  • Motion
  • Velocity and acceleration
  • Newton’s laws
  • Force and momentum
  • Equilibrium
  • Work, power and energy
Heat, Sound and Light

Energy transfer, waves, and optical behaviour.

  • Temperature and heat
  • Latent heat
  • Conduction, convection, radiation
  • Sound waves
  • Reflection and refraction
  • Mirrors and lenses
Electricity, Magnetism and Devices

Basic circuits, magnets, and applications.

  • Magnets and compass
  • Static and current electricity
  • Ohm’s Law
  • Cells and circuits
  • Electrical power
  • Common instruments
Rule: Physics should be studied through concept, unit, formula, example, and application. Do not memorize only definitions without understanding their use.
Formula and Concept Bank
Density
Density \(= \frac{Mass}{Volume}\)
SI unit: \(kg/m^3\)
Specific Gravity
Specific gravity \(= \frac{Density\ of\ substance}{Density\ of\ water}\)
It has no unit.
Velocity
Velocity \(= \frac{Displacement}{Time}\)
SI unit: \(m/s\)
Acceleration
Acceleration \(= \frac{Change\ in\ velocity}{Time}\)
SI unit: \(m/s^2\)
Force
\(F = ma\)
SI unit: newton \(N\)
Momentum
Momentum \(= mv\)
SI unit: \(kg\,m/s\)
Work
Work \(= Force \times Distance\)
SI unit: joule \(J\)
Ohm’s Law
\(V = IR\)
Voltage = Current × Resistance

Tip: Remember the physical meaning of every formula, not only the symbols.

Physics Problem-Solving Guide

Physics questions become easier when the student first identifies the concept and then recalls the related law, formula, unit, or application.

Question Type What to Use Typical Clue
Floating and sinking Density, specific gravity, Archimedes’ principle Buoyancy, upthrust, immersed body
Motion question Velocity, acceleration, Newton’s laws Speed changes, force, inertia
Energy question Work, power, energy Force, distance, rate of doing work
Heat question Temperature, latent heat, heat transfer Expansion, change of state, conduction
Optics question Reflection, refraction, mirrors, lenses Image, bending of light, focus
Electric circuit Ohm’s Law, current, voltage, resistance, power Battery, wire, bulb, switch, fuse
Exam shortcut: First identify the branch of Physics involved—mechanics, heat, sound, light, magnetism, or electricity. Then recall the matching law or principle.

Physical Properties and States of Matter

Matter is anything that has mass and occupies space. It commonly exists in three states: solid, liquid, and gas. Each state has different properties due to the arrangement and movement of particles.

State Shape Volume Particle Arrangement Example
Solid Fixed shape Fixed volume Particles closely packed Stone, iron, wood
Liquid No fixed shape Fixed volume Particles less tightly packed Water, oil, milk
Gas No fixed shape No fixed volume Particles far apart Air, oxygen, hydrogen
Remember: Solids have fixed shape and volume, liquids have fixed volume but no fixed shape, and gases have neither fixed shape nor fixed volume.

Mass, Weight, Volume, Density and Specific Gravity

These are basic physical quantities used to describe matter. Competitive exams often ask the difference between mass and weight, and the meaning of density and specific gravity.

Quantity Meaning Unit / Note Example Focus
Mass Amount of matter in a body. kilogram \(kg\) Does not change from place to place.
Weight Force with which Earth attracts a body. newton \(N\) Changes with gravity.
Volume Space occupied by a body. \(m^3\), litre, \(cm^3\) Measured by dimensions or displacement method.
Density Mass per unit volume. \(kg/m^3\) Higher density means more mass in same volume.
Specific Gravity Ratio of density of a substance to density of water. No unit Used in hydrometer readings.
Common trap: Mass and weight are not the same. Mass is amount of matter; weight is gravitational force on that mass.

Archimedes’ Principle, Pressure and Barometer

Fluids exert pressure and provide an upward force called buoyant force or upthrust. These ideas explain floating, sinking, hydrometers, ships, balloons, and barometers.

Concept Meaning Application
Archimedes’ Principle A body immersed in a fluid experiences an upward buoyant force equal to the weight of fluid displaced. Ships, submarines, hydrometers, floating bodies.
Pressure Force acting per unit area. Sharp knives, broad tyres, hydraulic machines.
Atmospheric Pressure Pressure exerted by air on all objects. Drinking through straw, barometer, weather changes.
Barometer Instrument used to measure atmospheric pressure. Weather forecasting and altitude estimation.
Remember: A body floats when its weight is balanced by the buoyant force. A barometer measures atmospheric pressure.

Motion, Velocity, Acceleration, Force and Momentum

Motion means change in position with time. Velocity tells how fast displacement changes, acceleration tells how fast velocity changes, and force is the cause that changes or tends to change the state of motion.

Term Meaning Formula / Unit
Rest A body is at rest if its position does not change with time. Relative concept
Motion A body is in motion if its position changes with time. Relative concept
Speed Distance travelled per unit time. \(m/s\)
Velocity Displacement per unit time in a given direction. \(m/s\)
Acceleration Rate of change of velocity. \(m/s^2\)
Force Push or pull that changes or tends to change motion. \(F = ma\), unit newton
Momentum Quantity of motion possessed by a moving body. \(p = mv\)
Exam focus: Speed is scalar, velocity is vector. Momentum depends on both mass and velocity.

Newton’s Laws of Motion and Parallelogram of Forces

Newton’s laws explain the relationship between force and motion. They are among the most important laws in elementary Physics.

Law / Principle Statement / Meaning Example
First Law A body remains at rest or in uniform motion unless acted upon by an external force. Passengers jerk forward when a moving bus stops suddenly.
Second Law Force is proportional to rate of change of momentum. Commonly, \(F = ma\). Greater force gives greater acceleration.
Third Law For every action, there is an equal and opposite reaction. Rocket propulsion, recoil of gun, walking.
Parallelogram of Forces If two forces acting at a point are represented by two adjacent sides of a parallelogram, their resultant is represented by the diagonal. Used to find resultant of two forces.
Memory aid: First law explains inertia, second law explains \(F = ma\), and third law explains action-reaction pairs.

Stability, Equilibrium, Gravitation, Work, Power and Energy

Bodies may be stable or unstable depending on their centre of gravity and base area. Gravitation explains attraction between masses. Work, power, and energy describe transfer and use of energy.

Concept Meaning Example / Formula
Equilibrium A body is in equilibrium when the net force and net turning effect are zero. Balanced beam, stable table.
Stability A body is more stable if it has a low centre of gravity and broad base. Racing cars are made low and wide.
Gravitation Force of attraction between masses. Earth attracts objects towards its centre.
Work Work is done when force moves a body through a distance. \(W = F \times s\)
Power Rate of doing work. \(P = \frac{Work}{Time}\)
Energy Capacity to do work. Kinetic energy, potential energy, heat energy.
Common trap: Work is not done in Physics unless displacement occurs in the direction of force.

Heat, Temperature, Change of State and Latent Heat

Heat is a form of energy that flows from a hotter body to a colder body. Temperature measures the degree of hotness or coldness of a body.

Concept Meaning Exam Focus
Heat Energy transferred due to temperature difference. Measured in joule or calorie.
Temperature Measure of hotness or coldness. Measured using thermometer.
Thermal Expansion Expansion of substances on heating. Railway gaps, mercury thermometer.
Change of State Conversion between solid, liquid, and gas. Melting, boiling, freezing, condensation.
Latent Heat Heat absorbed or released during change of state without change in temperature. Ice melting at \(0^\circ C\), water boiling at \(100^\circ C\).
Remember: During change of state, temperature remains constant even though heat is being absorbed or released.

Modes of Transfer of Heat

Heat can be transferred from one place to another by conduction, convection, and radiation. These three modes are important in daily life and scientific instruments.

Mode Meaning Medium Required? Example
Conduction Transfer of heat through solids without movement of particles from place to place. Yes Metal spoon becoming hot in tea.
Convection Transfer of heat by movement of fluid particles. Yes, in liquids and gases Sea breeze, boiling water.
Radiation Transfer of heat without any material medium. No Heat from the Sun reaching Earth.
Exam shortcut: Solids mainly conduct heat, liquids and gases transfer heat by convection, and heat from the Sun reaches us by radiation.

Sound Waves and Simple Musical Instruments

Sound is produced by vibrating bodies. It travels in the form of waves and requires a material medium such as air, water, or solids.

Term Meaning Example / Note
Sound Wave A disturbance produced by vibration and travelling through a medium. Sound cannot travel through vacuum.
Frequency Number of vibrations per second. Determines pitch.
Amplitude Maximum displacement of vibrating particles. Determines loudness.
Wavelength Distance between two consecutive compressions or rarefactions. Related to wave speed.
Musical Instruments Produce sound through vibrating strings, air columns, or membranes. Guitar, flute, drum, harmonium, violin.
Remember: Pitch depends on frequency, loudness depends on amplitude, and sound needs a medium to travel.

Light: Rectilinear Propagation, Reflection and Refraction

Light is a form of energy that enables vision. It travels in straight lines in a uniform medium. Its behaviour changes when it strikes a surface or passes from one medium to another.

Concept Meaning Example
Rectilinear Propagation Light travels in straight lines in a uniform medium. Formation of shadows, pinhole camera.
Reflection Bouncing back of light from a surface. Plane mirror, periscope.
Refraction Bending of light when it passes from one medium to another. Pencil appearing bent in water.
Dispersion Splitting of white light into colours. Rainbow, prism.
Exam focus: Shadows prove straight-line travel of light. Reflection is used in mirrors; refraction is used in lenses.

Spherical Mirrors, Lenses and Human Eye

Mirrors form images by reflection, while lenses form images by refraction. The human eye acts like an optical instrument and uses a convex lens to focus light on the retina.

Device / Part Type / Meaning Use / Function
Concave Mirror Reflecting surface curved inward. Used in shaving mirrors, headlights, solar cookers.
Convex Mirror Reflecting surface curved outward. Used as rear-view mirror because it gives wide field of view.
Convex Lens Thicker at centre, converges light rays. Magnifying glass, camera, human eye.
Concave Lens Thinner at centre, diverges light rays. Used to correct myopia.
Retina Light-sensitive screen of the eye. Image is formed on retina.
Iris and Pupil Iris controls size of pupil. Controls amount of light entering eye.
Remember: Convex lens converges light, concave lens diverges light. Convex mirror gives a wide field of view.

Magnets and Earth as a Magnet

Magnets attract substances like iron, nickel, and cobalt. They have two poles: north pole and south pole. Earth itself behaves like a huge magnet.

Concept Meaning Important Point
Natural Magnet Magnet found in nature. Lodestone is a natural magnet.
Artificial Magnet Magnet made by humans. Bar magnet, horseshoe magnet, electromagnet.
Magnetic Poles Ends of a magnet where magnetic force is strongest. North pole and south pole.
Law of Magnetism Like poles repel and unlike poles attract. N-N repel, N-S attract.
Earth as a Magnet Earth behaves like a giant magnet. Used in mariner’s compass.
Exam shortcut: A freely suspended magnet always points approximately in the north-south direction.

Static Electricity, Current Electricity and Ohm’s Law

Electricity may be static or current. Static electricity is charge at rest, while current electricity is the flow of electric charge through a conductor.

Concept Meaning Example / Formula
Static Electricity Electric charges at rest. Comb attracting paper bits after rubbing.
Current Electricity Flow of electric charge. Current in a wire connected to a cell.
Conductor Allows electric current to pass through it. Copper, aluminium, iron.
Non-conductor / Insulator Does not allow current to pass easily. Rubber, plastic, dry wood, glass.
Ohm’s Law Current through a conductor is directly proportional to potential difference, if temperature remains constant. \(V = IR\)
Simple Circuit Closed path for current to flow. Cell, wire, switch, bulb.
Remember: Current flows only in a closed circuit. Rubber and plastic are used as insulators for safety.

Effects of Current, Electrical Power, Cells and X-Rays

Electric current produces several effects such as heating, lighting, and magnetic effects. These effects are used in appliances, instruments, machines, and safety devices.

Topic Meaning / Principle Use / Example
Heating Effect Current produces heat when it passes through resistance. Electric iron, heater, fuse.
Lighting Effect Electrical energy changes into light energy. Bulb, tube light, LED.
Magnetic Effect Current-carrying conductor produces magnetic field. Electromagnet, electric bell, motor.
Electrical Power Rate of consumption of electrical energy. \(P = VI\), unit watt.
Primary Cell Cell that cannot be recharged easily. Dry cell.
Secondary Cell Cell that can be recharged. Lead-acid battery, rechargeable battery.
X-Rays High-energy electromagnetic radiation with high penetrating power. Medical imaging, checking internal cracks, security scanning.
Safety note: X-rays are useful in medicine and industry, but exposure must be controlled because they can affect living tissues.

Working Principles of Common Devices and Instruments

Many everyday devices work on simple principles of mechanics, heat, fluids, sound, light, magnetism, or electricity. The table below gives the exam-oriented principle behind each device.

Device / Instrument Principle Use / Explanation
Simple Pendulum Periodic motion under gravity. Used to understand time period and oscillations.
Simple Pulley Changes direction of force. Used to lift loads conveniently.
Siphon Atmospheric pressure and gravity. Transfers liquid from higher level to lower level.
Lever Principle of moments. Used to lift or move loads with less effort.
Balloon Buoyancy in air. Hot air or lighter gas helps it rise.
Pump Pressure difference. Used to lift or move fluids.
Hydrometer Archimedes’ principle. Measures relative density or specific gravity of liquids.
Pressure Cooker Increase in pressure raises boiling point of water. Cooks food faster.
Thermos Flask Reduces conduction, convection, and radiation. Keeps liquids hot or cold for longer time.
Gramophone Conversion of mechanical vibrations into sound. Reproduces recorded sound.
Telegraph Magnetic effect of electric current. Used historically for long-distance coded messages.
Telephone Conversion of sound energy into electrical signals and back to sound. Used for voice communication.
Periscope Reflection of light by plane mirrors or prisms. Used to see objects from hidden positions.
Telescope Refraction or reflection of light. Used to view distant objects.
Microscope Magnification using lenses. Used to view very small objects.
Mariner’s Compass Earth’s magnetism. Used for direction finding.
Lightning Conductor Provides safe path for electric discharge to the Earth. Protects buildings from lightning.
Safety Fuse Heating effect of current. Melts and breaks circuit when excessive current flows.
Exam focus: Learn each device with one principle and one use. This is a high-scoring factual area in Physics.

Step-by-Step Physics Learning Method

Step Action Example Focus
Step 1 Identify the branch of Physics. Mechanics, heat, sound, light, magnetism, electricity.
Step 2 Learn the definition and unit. Force in newton, power in watt, energy in joule.
Step 3 Connect the concept with an example. Barometer measures pressure; fuse protects circuits.
Step 4 Remember the law or principle. Newton’s laws, Archimedes’ principle, Ohm’s Law.
Step 5 Practice comparison-based questions. Mass vs weight, heat vs temperature, conductor vs insulator.
Important: For Physics, revise definitions, units, laws, formulas, devices, and everyday applications together.

Solved Examples

Question Explanation Answer
Which physical quantity is mass per unit volume? Density is defined as mass divided by volume. Density
Which instrument measures atmospheric pressure? A barometer is used to measure atmospheric pressure. Barometer
Which law explains inertia? Newton’s First Law states that a body continues in rest or uniform motion unless acted upon by external force. Newton’s First Law
What is the SI unit of power? Power is the rate of doing work. Its SI unit is watt. Watt
Which mode of heat transfer does not require a medium? Radiation can take place even through vacuum. Radiation
Which mirror is used as a rear-view mirror in vehicles? Convex mirror gives a wide field of view and forms diminished images. Convex mirror
What does a safety fuse use? A fuse melts due to heating effect of excessive current and breaks the circuit. Heating effect of current
Which instrument works on Earth’s magnetism? A mariner’s compass uses a magnetic needle that aligns north-south. Mariner’s compass

Note: In Physics, many questions are direct but require clarity in definition, principle, instrument, and use.

Common Traps and Shortcuts

Common Traps
  • Confusing mass and weight.
  • Calling speed and velocity the same in all cases.
  • Forgetting that sound cannot travel in vacuum.
  • Confusing heat with temperature.
  • Mixing up conduction, convection, and radiation.
  • Confusing concave and convex mirrors.
  • Thinking current flows in an open circuit.
  • Forgetting that a fuse works on heating effect of current.
  • Confusing primary and secondary cells.
Useful Shortcuts
  • Mass is constant; weight changes with gravity.
  • Density = mass per unit volume.
  • Barometer measures atmospheric pressure.
  • Newton’s First Law explains inertia.
  • Radiation does not need a medium.
  • Pitch depends on frequency.
  • Convex mirror gives wide field of view.
  • Ohm’s Law: \(V = IR\).
  • Compass works due to Earth’s magnetism.
Exam approach: For every device, remember the principle. For every physical quantity, remember its meaning and unit. For every law, remember one practical example.

Practice

A) Multiple Choice Questions
  1. The SI unit of force is:
    Joule Newton Watt Pascal
  2. Which instrument measures atmospheric pressure?
    Thermometer Barometer Hydrometer Ammeter
  3. Heat from the Sun reaches Earth mainly by:
    Conduction Convection Radiation Reflection
  4. Which mirror is used as a rear-view mirror in vehicles?
    Plane mirror Concave mirror Convex mirror Cylindrical mirror
  5. Ohm’s Law is represented by:
    \(P = VI\) \(F = ma\) \(V = IR\) \(W = Fs\)
B) Short Answer Questions
  1. Differentiate between mass and weight. (Hint: Amount of matter vs gravitational force.)
  2. State Archimedes’ principle. (Hint: Upthrust equals weight of fluid displaced.)
  3. What is latent heat? (Hint: Heat absorbed or released during change of state without temperature change.)
  4. Why is a convex mirror used in vehicles? (Hint: Wide field of view.)
  5. What is the use of a safety fuse? (Hint: Protects circuit from excessive current.)
C) Match the Device with the Correct Principle
Device / Concept Correct Principle / Meaning
Hydrometer Archimedes’ principle
Pressure Cooker Increased pressure raises boiling point
Thermos Flask Reduces heat transfer
Periscope Reflection of light
Microscope Magnification using lenses
Compass Earth’s magnetism
Safety Fuse Heating effect of current
Barometer Measures atmospheric pressure
Physics Reminder

Physics develops the ability to understand matter, motion, forces, heat, sound, light, magnetism, electricity, and the principles behind everyday instruments. It is a highly practical chapter and should be revised through examples, units, laws, and applications.

Task: Create five Physics questions using one question each from mechanics, heat, sound, light, and electricity.

Show Suggested Answers
Multiple Choice
  1. Newton
    The SI unit of force is newton.
  2. Barometer
    A barometer is used to measure atmospheric pressure.
  3. Radiation
    Heat from the Sun reaches Earth through radiation, which does not require a material medium.
  4. Convex mirror
    Convex mirrors give a wider field of view and are used as rear-view mirrors.
  5. \(V = IR\)
    Ohm’s Law states that voltage equals current multiplied by resistance.
Short Answer Questions
  1. Mass is the amount of matter in a body and remains constant. Weight is the gravitational force acting on a body and changes with gravity.
  2. Archimedes’ principle states that a body immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced by it.
  3. Latent heat is the heat absorbed or released during change of state without change in temperature.
  4. A convex mirror is used in vehicles because it gives a wide field of view and helps the driver see more area behind the vehicle.
  5. A safety fuse protects an electric circuit by melting and breaking the circuit when excessive current flows.
Concept Matching
  1. Hydrometer → Archimedes’ principle
  2. Pressure Cooker → Increased pressure raises boiling point
  3. Thermos Flask → Reduces heat transfer
  4. Periscope → Reflection of light
  5. Microscope → Magnification using lenses
  6. Compass → Earth’s magnetism
  7. Safety Fuse → Heating effect of current
  8. Barometer → Measures atmospheric pressure
Clue Explanation

Physics questions usually become easy when the concept is linked with a law, instrument, unit, or everyday application. For example, hydrometer connects with Archimedes’ principle, compass connects with magnetism, and fuse connects with heating effect of current.

Exam tips
  • Learn units of common physical quantities.
  • Differentiate mass and weight clearly.
  • Remember laws with examples.
  • Connect heat transfer modes with daily examples.
  • Know uses of mirrors and lenses.
  • Revise Ohm’s Law and simple circuits.
  • Study device-principle pairs carefully.
  • Practice one-line conceptual questions regularly.
Practice MCQs