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Heat Expansion - Solid

  • Heating Metals

    • When a metal is heated:
    • Temperature: Increases
    • Volume: Increases
    • Density: Decreases
    • Kinetic Energy: Increases as particles vibrate more

  • Bimetallic Strip

    • Composed of two thin strips of different metals joined together
    • Metals expand at different rates when heated, causing the strip to bend
    • Example:
      • Aluminium expands the most
      • Invar expands the least
    • Applications:
    1. Thermostats:
      • Bending action controls and regulates temperature for devices like air conditioners
    2. Fire Alarms:
      • Bending can close an electrical circuit, triggering the alarm

Heat Expansion - Liquid

  • Thermometry Example:

    • As the temperature increases from 20°C to 25°C,
    • Mass: Stays the same
    • Kinetic Energy: Increases
    • Volume: Increases
    • Density: Metrics define that density of most liquids decreases with temperature increase

  • Special Characteristic of Water

    • Water expands when temperature decreases from 4°C to 0°C, leading to ice floating
    • Ice (solid form of water) is less dense than liquid water

Heat Expansion - Gas

  • Gas Heating Effects:

    • Upon heating, gas particles gain kinetic energy leading to an expansion.
    • Example:
      • If a gas inside a balloon is heated too much, it may expand and cause the balloon to explode

  • Material Classes Based on Heat Transfer:

    • Conductors: Allow easy heat transfer (e.g., pans)
    • Insulators: Slow down heat transfer (e.g., thermos)

Heat Transfer Methods

  • Conduction:

    • Heat transfer through neighboring particles (e.g., hot frying pan)

  • Convection:

    • Heat transfer in fluids (liquid and gas)
    • Process: Hot air rises while cold air sinks

  • Radiation:

    • Heat transfer through space without needing particles
    • Eg.: Heat from the sun

Evaporation

  • Heat is transferred from the surface of liquids

  • Evaporation occurs when:

    1. Particles gain enough energy to break attractive forces between them
    2. Surface area increases, which accelerates evaporation
      • Example: Water in a larger container evaporates faster than in a smaller one
      • Wind enhances evaporation by carrying away water vapor

  • Cooling Effect of Sweating:

    • As sweat evaporates, it takes heat away from the body, helping in cooling

Light Properties

  • Luminous vs. Non-Luminous:

    • Luminous: Objects producing light (e.g., the Sun)
    • Non-Luminous: Objects that do not produce light (e.g., earphones)

  • Reflection Types:

    • Specular Reflection: Smooth surfaces reflect light evenly
    • Diffuse Reflection: Rough surfaces scatter light

  • Rectilinear Propagation:

    • Light travels in straight lines

  • Law of Reflection:

    • Angle of incidence = Angle of reflection

  • Refraction: Light bends when entering a different medium

    • Refraction occurs when light travels from less dense to more dense medium

Dispersion of Light

  • Dispersion:

    • Light separates into colors based on wavelengths
    • Primary Colors: Red, Green, Blue
    • Secondary Colors: Created from mixing primary colors
      • Example: Green + Blue = Cyan, Red + Green = Yellow, Red + Blue = Magenta

  • Absence of Light:

    • Black is the result of no visible light being present

  • Critical Angles and Total Internal Reflection

    • Critical Angle: Angle of incidence for which the angle of refraction is 90°
    • Total Internal Reflection used in optical instruments like prisms, endoscopes, and fiber optics

  • Applications of Total Internal Reflection:

    1. Cat's Eye
    2. Periscope
    3. Binoculars
    4. Optical Fibres
    5. Diamond cutting