Physics O-levels notes

Physics

Physics is the study of matter, energy, their properties, and relationships in various fields like General Physics, Thermal Physics, Light, Waves & Sound, Electricity & Magnetism, and Radioactivity.

Physical Quantity

A physical quantity is a measurable quantity consisting of a numerical magnitude and a unit.

SI Units

The International System of Units (SI) includes basic physical quantities like length (meter), mass (kilogram), time (second), electric current (ampere), thermodynamic temperature (kelvin), and amount of substance (mole).

SI Unit Prefixes

Prefixes for SI units facilitate expressing large or small quantities conveniently.

Standard Form

Physical quantities can be expressed in standard form, like 9.9 x 10^9 m.

Measurement of Length

Instruments like measuring tape, meter rule, digital calipers, and micrometer screw gauge are used to measure length accurately.

Measurement of Time

Time is measured in seconds, and stopwatch timings are taken to 1 decimal place.

Scalar & Vectors

Scalar quantities have only magnitude, while vector quantities have magnitude and direction.

Newton’s Laws of Motion

Newton's laws describe the effects of forces on the motion of objects and include principles like inertia, acceleration, and action-reaction forces.

Turning Effects of Forces

The moment of a force (M = Fd) and the principle of moments are essential in understanding the turning effects of forces and preventing objects from toppling.

Pressure

Pressure is defined as force per unit area (P = F/A) and is crucial in various applications like pressure transmission in enclosed liquids.

Energy Stores & Transfers

Energy can be stored in various forms like chemical potential, kinetic, gravitational potential, and transferred through different pathways like mechanically, thermally, electromagnetically, and electrically.

Work Done & Power

Work done is the product of force and distance (W = Fs), while power is the rate of doing work or transferring energy per unit time (P = W/t).

Major Energy Resources

Understanding major energy resources like fossil fuels, nuclear fuels, biofuels, wind, tides, hydropower, geothermal reservoirs, and solar power is crucial for energy sustainability.

Solid

Particles vibrate about fixed positions, held by strong attractive forces, with a fixed volume and shape.

Liquid

Particles slide over each other, arranged less closely than in solids, with a fixed volume but no fixed shape.

Gas

Particles move freely, far apart in irregular patterns, with no fixed volume or shape.

Temperature

Directly related to the average kinetic energy of particles in a body.

Pressure

Average force exerted by particles per unit area, proportional to temperature.

Thermal Equilibrium

State where objects have the same temperature, with no net transfer of energy between them.

Conduction

Transfer of energy through vibrational motion from one particle to another, effective in solids.

Convection

Energy transfer through convection currents of a fluid due to density differences.

Radiation

Energy transfer by electromagnetic waves without a medium, influenced by surface temperature and area.

Internal Energy

Total kinetic and potential energy associated with particle motion and interactions in a system.

Specific Heat Capacity

Amount of energy needed to change the temperature of a unit mass of a material by one degree.

Latent Heat

Energy absorbed or released during a change of state at constant temperature.

Wave

Disturbance propagating through space transferring energy without matter.

Refraction

Bending of light as it passes from one optical medium to another.

Total Internal Reflection

Complete reflection of light in an optically denser medium at the boundary with a less dense medium.

Converging Lens

Lens that converges parallel rays to a point, with a focal point and focal length.

Virtual Image

The perception of an image by our eyes that is not physically present but appears real.

Electric Field

A region surrounding an electric charge where another charge would experience an electric force.

Coulomb

The SI unit of electric charge, equivalent to the charge transported by a constant current of one ampere in one second.

Electron Affinity

The tendency of an atom to attract electrons, leading to the transfer of electrons between objects with different affinities.

Electroscope

An instrument used to detect the presence and magnitude of electric charge.

Induction

The process of redistributing electric charges in an object by bringing a charged object close to it without direct contact.

Neutralizing

The process of discharging excess electric charge from an object to neutralize it.

Electrostatic Charging

The accumulation of electric charge on an object through contact, friction, or induction.

Electromotive Force (e.m.f.)

The work done per unit charge in driving charges around a complete circuit.

Potential Difference (p.d.)

The work done per unit charge in driving charges through a component in an electric circuit.

Series Circuit

Components connected in a single loop where the total potential difference supplied to the circuit equals the sum of individual potential differences of the resistors.

Effective Resistance in Series Circuit

The sum of individual resistances in a series circuit, which is equivalent to the total resistance.

Parallel Circuit

Components connected in branches where the total current flowing in/out of the branches equals the sum of the individual branch currents.

Potential Divider

A circuit that divides the voltage using resistors in series, allowing for different voltage outputs across the resistors.

Transducers in Potential Dividers

Electronic devices that convert physical condition changes into electrical signals, used to vary voltage output in potential dividers.

Thermistors

Input transducers that vary resistance with temperature, used to measure temperature accurately and cost-effectively.

Light-Dependent Resistors (LDRs)

Input transducers that vary resistance with light intensity, used to measure light levels accurately.

Diode

A semiconductor device that conducts current only in the forward direction, allowing unidirectional current flow.

Electrical Energy Consumption

The energy used by electrical appliances, measured in kilowatt-hours (kWh) and calculated by multiplying power rating by time.

Electrical Hazards

Dangers like damaged insulation, cable overheating, and damp conditions that can cause burns, electric shocks, and fires in electrical systems.

Electromagnetic Induction

The process of generating an electromotive force (e.m.f.) in a circuit by changing the magnetic flux through the circuit.

Faraday’s Law

States that the magnitude of the induced e.m.f. in a circuit is directly proportional to the rate of change of magnetic flux through the circuit.

Lenz’s Law

States that the direction of the induced e.m.f. and the induced current in a closed circuit will be such that they oppose the motion or change producing it.

Fleming’s Right-Hand Rule

A rule used to determine the direction of the induced current in a conductor moving in a magnetic field.

Fleming’s Left-Hand Rule

A rule used for electric motors to determine the direction of force acting on a current-carrying conductor in a magnetic field.

Transformers

Devices that change high alternating voltage to low alternating voltage or vice versa through electromagnetic induction between primary and secondary coils.

Step-up Transformers

Transformers where the secondary voltage is greater than the primary voltage.

Step-down Transformers

Transformers where the secondary voltage is less than the primary voltage.

Ohmic Heating

The heating effect caused by the resistance in a conductor when current flows through it, leading to power loss.

Ideal Transformer

A theoretical transformer where energy transfer between coils is 100% efficient, following the laws of conservation of energy.