A Level Physics CAIE

This subject is broken down into 76 topics in 25 modules:

  1. Physical Quantities and Units 4 topics
  2. Kinematics 1 topics
  3. Dynamics 3 topics
  4. Forces, Density and Pressure 3 topics
  5. Work, Energy and Power 2 topics
  6. Deformation of Solids 2 topics
  7. Waves 5 topics
  8. Superposition 4 topics
  9. Electricity 3 topics
  10. D.C. Circuits 3 topics
  11. Particle Physics 2 topics
  12. A2: Motion in a Circle 2 topics
  13. A2: Gravitational Fields 4 topics
  14. A2: Temperature 3 topics
  15. A2: Ideal Gases 3 topics
  16. A2: Thermodynamics 2 topics
  17. A2: Oscillations 3 topics
  18. A2: Electric Fields 5 topics
  19. A2: Capacitance 3 topics
  20. A2: Magnetic Fields 5 topics
  21. A2: Alternating Currents 2 topics
  22. A2: Quantum Physics 4 topics
  23. A2: Nuclear Physics 2 topics
  24. A2: Medical Physics 3 topics
  25. A2: Astronomy and Cosmology 3 topics
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  • 25
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  • 76
    topics
  • 29,731
    words of revision content
  • 3+
    hours of audio lessons

This page was last modified on 28 September 2024.

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Physics

Physical Quantities and Units

Physical Quantities

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Physical Quantities

Understanding Physical Quantities

  • A Physical Quantity is any measurable quantity that can be described using mathematical operations.

  • There are two types of physical quantities: scalar quantities and vector quantities.

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

  • Scalar quantities include mass, temperature, speed, energy, work, and power.

  • Vector quantities include displacement, velocity, force, and acceleration.

Base Quantities

  • There are seven base quantities in physics: Length (metre, m), Mass (kilogram, kg), Time (second, s), Electric Current (ampere, A), Thermodynamic Temperature (kelvin, K), Amount of Substance (mole, mol), and Luminous Intensity (candela, cd).

  • The units of these base quantities are called the base units. All other physical quantities are derived from these base units.

Derived Quantities

  • A derived quantity can be defined in terms of the base quantities. Examples include area, volume, speed, acceleration, force, energy, and power.

  • These quantities have derived units, which are combinations of the base units. For example, speed (a derived quantity) has a unit of m/s (a derived unit).

Units and Measurement

  • In physics, it’s essential to use a consistent set of units for measurements. This allows for accurate calculations and comparisons.

  • The International System of Units (SI) is the universally accepted system of measurement in science. It is based on the seven base units and derived units.

  • Some units are derived from named quantities, like the Newton (force), Pascal (pressure), Watt (power), and so on.

  • It's also imperative to understand the conversion between different units. For example, 1km = 1000m.

Errors in Measurements

  • Measurements are not always perfect and may have errors. Error is the discrepancy between the measured value and the true value.

  • There are random errors and systematic errors. Random errors vary unpredictably from measurement to measurement, while systematic errors are consistent, repeatable errors.

  • It's important to identify the sources of error and mitigate them as much as possible to obtain more accurate results.

Using Prefixes for Units

  • In physics, prefixes are commonly used with units to change their order of magnitude. For example, kilo (k) means 1000, mega (M) means a million, and milli (m) means thousandth.

  • Understanding the prefixes and their respective multipliers is crucial for converting between different units.

Dimensional Analysis

  • Dimensional analysis is a method used to check the validity of an equation. It involves comparing the dimensions of the physical quantities on each side of the equation.

  • It's also useful to derive the units of a physical quantity in a given equation. For example, the dimensional formula for speed is [M^0 L^1 T^-1].

Course material for Physics, module Physical Quantities and Units, topic Physical Quantities

Physics

A2: Temperature

Thermal Equilibrium

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Thermal Equilibrium

Understanding Thermal Equilibrium

  • Thermal equilibrium is achieved when two systems, upon contact, reach the same temperature and no heat transfers between them.
  • This state assumes the systems are isolated, meaning no heat is lost to the surroundings.
  • The zeroth law of thermodynamics formalises the concept of thermal equilibrium: if two systems are separately in thermal equilibrium with a third system, they are also in thermal equilibrium with each other.

The Concept of Temperature

  • In the context of thermal equilibrium, temperature can be considered the property that determines the direction of heat flow.
  • Heat always flows from the higher-temperature system to the lower-temperature system until equilibrium is reached.
  • Temperature is measured in degrees Celsius (°C) or Kelvin (K) in physical science. The Kelvin scale starts at absolute zero, with each increment equal to one degree on the Celsius scale.

Thermal Equilibrium and Energy Transfer

  • In a closed system, the total energy remains constant. This includes all forms of energy, including heat and work.
  • When systems are at different temperatures, heat transfer (also called a heat flux) proceeds from the hotter to the cooler system.
  • Conduction, convection, and radiation are the three primary means by which thermal equilibrium can be achieved through heat transfer.

Consequences and Applications of Thermal Equilibrium

  • Knowledge of thermal equilibrium is crucial for understanding interactions in thermodynamic systems.
  • Applications include the design of heating and cooling systems, manufacturing processes, and the performance of engines and refrigerators.
  • At thermal equilibrium, all parts of a system have the same macroscopic state.
  • Any changes in a system at thermal equilibrium must be slow enough that the system effectively remains in equilibrium at all times. This concept is known as the quasi-static approximation.

Course material for Physics, module A2: Temperature, topic Thermal Equilibrium

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