Theme B and Theme E Physics (2)

B.1 Thermal Energy Transfers

Thermal Concepts

• Temperature and Heat Flow: Heat transfers from hot to cold objects when they are in thermal contact, determined by their temperature difference.

• Equilibrium: Objects reach thermal equilibrium when they have the same temperature.

• Heat Definition: Heat is not a substance, but the transfer of thermal energy, often measured in calories or joules.

• Temperature Scales: Common scales include Celsius (°C) and Kelvin (K). The relationship is T(K) = t(°C) + 273.

Specific Concepts in Gases

• Pressure (P): Force exerted per unit area. SI units: Nm⁻² or Pascals (Pa).

• Volume (V): Measured in m³ or cm³.

• Temperature (t): Measured in °C or K.

• Density (p): Calculated as p = m/V, where m is mass in kg and V is volume in m³.

B.2 Heat and Internal Energy

Microscopic vs. Macroscopic Views

• Macroscopic: Looks at the system as a whole and how it interacts with its surroundings.

• Microscopic: Examines interactions at the atomic and molecular levels.

Internal Energy

• An object gains or loses energy as its temperature changes, which can be in kinetic or potential forms.

• Total internal energy (U) is the sum of kinetic and potential energy at the molecular level.

Kinetic Theory

• States of Matter:

  • Solids: Fixed volume and shape with particles vibrating in place.

  • Liquids: Fixed volume but changing shape, particles can move around each other.

  • Gases: No fixed volume or shape, particles move independently and collide.

B.3 Specific Heat Capacity

Definitions and Measurements

• Thermal Capacity (C): Energy required to raise temperature by 1 K; Specific Heat Capacity (c) is energy required to raise 1 kg of a substance by 1 K.

• Methods for measuring include:

  1. Electrical method (involving heat input & temperature changes).

  2. Method of mixtures (using known heat capacities and temperature changes).

B.4 Phases of Matter and Latent Heat

Phase Changes

• When a substance changes phase (e.g., melting, boiling), temperature remains constant, but thermal energy is absorbed or released.

• Specific Latent Heat (L): Energy absorbed/released per unit mass during phase changes.

Measuring Latent Heats

• Methods involve calorimetry and calculations using energy balances during phase transitions.

B.5 Thermal Energy Transfer Processes

Conduction

• Definition: Heat transfer through matter without any bulk movement.

• Mechanism: Kinetic energy transfer through particle collisions.

• Materials: Good conductors (metals) vs. insulators (wood, air).

Convection

• Definition: Transfer of heat through liquid or gas movement due to density differences.

• Example: Warm air rising and cool air sinking creates currents.

Radiation

• Definition: Transfer of energy through electromagnetic waves, doesn't require a medium.

• Examples: Sun warming Earth, heat from a fire.

B.6 Additional Notes on Thermal Energy

Key Takeaways

• Most substances can be modeled with thermal concepts including specific heat, latent heat, and phase changes affecting interactions at the atomic level.

Understanding Radiation Laws

• Inverse Square Law: Intensity of radiation drops with the square of the distance from the source, applies to all waves.

Gravitational Fields (D.1)

Key Concepts

• Newton’s Law of Gravitation: Describes how every mass attracts every other mass, F = G(m₁m₂)/r².

Gravitational Field Strength (g)

• Defined as the force per unit mass (N/kg), varies by distance from mass.

Orbit Dynamics

• Kepler’s Laws: Governs orbital motion, including relationships between the orbital period and radius.

Stability and Nuclear Forces

• Strong nuclear forces work at very short ranges to keep nucleons together. Weak forces engage with beta decay processes.

Nuclear Stability and Decay

• Isotopes stabilize differently; binding energy plays a crucial role in decay processes.

Electric Fields (D.2)

Electric Charge and Forces

• Charges produce electric fields; Coulomb's law defines their interactions.

Electric Field Strength (E)

• Defined as force on a unit charge (N/C or V/m), represented with field lines indicating direction and intensity.

Electric Potential Energy

• Defines energy per charge related to the electric field and is integral in determining work done in moving charges between points in the field.

Quantum Concepts (E.2)

Phenomena of Wave-Particle Duality

• Light and matter exhibit both particle-like and wave-like properties captured in phenomena such as the photoelectric effect and Compton scattering.

Matter Waves

• De Broglie's hypothesis equates the motion of particles with wave characteristics, influencing calculations for momentum and wavelength.

Radioactivity (E.3)

Types of Radiation

• Radioactive decay emits alpha, beta, or gamma radiation, each possessing unique ionizing properties affecting biological structures.

Decay Processes and Chain Reactions

• Chain reactions are crucial in nuclear fission processes, often regulated to prevent uncontrolled reactions.

Uses of Radioactivity

• Applications in medical diagnostics, treatments, sterilization processes, and illumination of processes such as carbon dating.

Key Calculations

• Half-life calculations allow the determination of remaining quantities of radioactive materials, critical in understanding the longevity of isotopes.