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Comm science - Coggle Diagram

- - - - waves which oscillations are parallel to the direction of travel
      - examples
        
        sound waves
      - compression is the part of the wave where the particles are closer together
      - rarefaction is the part of the wave where the particles are further apart
    - - waves which oscillations are perpendicular to the direction of travel
      - examples
        
        light waves
        
        radio waves
  - - - the displacement of the particles from the rest position
        (distance from equilibrium to crest)
      - the bigger the amplitude, the greater energy the waves carry
    - - The amount of complete waves produced per unit time
      - Hz (Hertz)
    - - time it takes for a particle in a wave to complete 1 cycle
      - in seconds
    - - highest point on a transverse wave
    - - lowest point on a transverse wave
    - - the undisturbed position of particles when they are not vibrating.
    - - the shortest distance between any two points in a wave
  - - - speed = frequency x wavelength
    - - Period is 1 over frequency
      - F = 1 / T
    - - Distance / time = wavelength / period
  - - - are transverse waves
      - all can travel through vacuum, with a speed of 3.0 x 10⁸ m/s
      - exhibit waves properties such as reflection and refraction
      - transfer energy from one place to another
      - when travelling in different mediums, frequency does not change, only speed and wavelength
    - - Radio waves
        
        Uses
        
        radio
        
        television communications
        
        Type of radio waves
        
        Low Frequency (LF)
        
        30 - 300kHz
        
        wavelength: 10m - 2km
        
        Medium frequency (MF)
        
        300 kHz - 3MHz
        
        wavelength: 10m - 2km
        
        AM (amplitude modulated) radio
        
        submarine communications
        
        High frequency (HF)
        
        3 - 30 MHz
        
        wavelength: 10m - 2km
        
        Very High Frequency (VHF)
        
        30 - 300 MHz
        
        wavelength: 10m - 2km
        
        FM (frequency modulated) radio
        
        over-the-air television (terrestrial tv)
        
        Ultra High Frequency (UHF)
        
        300 MHz - 3 GHz
        
        wavelength: 10m - 2km
        
        terrestrial television
        
        bluetooth
        
        cellular phones
        
        wi-fi
      - microwaves
        
        Uses
        
        satellite television
        
        microwave oven
      - Infra-red
        
        Uses
        
        infra-red remote controller
        
        intruder alarms
        
        radiators (room heater)
      - visible light
        
        Uses
        
        optical fibres for:
        
        medical uses
        
        telecommunications
        
        Types of movement of light
        
        Refraction
        
        Definition
        
        bending of light when travelling from one medium to another
        
        Caused by change in speed of light as it passes from medium to medium
        
        refractive index
        
        4 more items...
        
        Types of rays / lines
        
        Normal
        
        1 more item...
        
        angle of incidence
        
        1 more item...
        
        angle of refraction
        
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        how it bends
        
        Enters optically denser medium
        
        2 more items...
        
        Enters optically less dense medium
        
        2 more items...
        
        Scenario
        
        When the incident ray is perpendicular to the surface of the glass block ( i = 0°), the ray of light is not deflected.
        
        Critical angle
        
        Can only occur when light travels from an optically denser medium to an optically less dense medium
        
        The critical angle ( c ) is the angle of incidence in the optically denser medium for which the angle of refraction ( r ) in the optically less dense medium is 90°.
        
        Total internal reflection
        
        Happens when the light travels from a medium of higher optical density to a medium of lower optical density
        
        and when the incident angle is larger than the critical angle
        
        When total internal reflection occurs, an incident ray is reflected back in the same medium.
        
        1 more item...
        
        Applications
        
        1 more item...
        
        if angle of incidence = critical angle
        
        2 more items...
        
        Refraction of light in a prism
        
        Dispersion of light is the separation of light into its component colours.
        
        prism refracts light at different speeds
        
        2 more items...
        
        colours
        
        1 more item...
        
        colours
        
        Coloured objects in white light
        
        3 more items...
        
        definition
        
        1 more item...
        
        Coloured objects in coloured light
        
        2 more items...
        
        mixing colours
        
        1 more item...
        
        Reflection of light
        
        light being bounced off after hitting a surface.
        
        allows us to see objects in our surroundings
        
        Types of rays / angles
        
        Incident ray
        
        1 more item...
        
        reflected ray
        
        1 more item...
        
        normal
        
        1 more item...
        
        angle of incidence
        
        1 more item...
        
        angle of reflection
        
        1 more item...
        
        Regular and irregular surfaces
        
        smooth surface (regular)
        
        2 more items...
        
        rough surface (irregular)
        
        2 more items...
        
        How to draw
        
        characteristics of an image formed by a mirror
        
        Same size and same shape as object
        
        upright
        
        laterally inverted
        
        Virtual
        
        same distance from mirror as person is to mirror
        
        Uses
        
        Blind corner mirrors (curved mirrors)
        
        Satellite dish (curved surface)
        
        periscope
      - ultraviolet (UV)
        
        Uses
        
        sunbeds
        
        sterilisation
        
        fluorescent tube
      - X-rays
        
        Uses
        
        x ray radiography
        
        finding flaws in metal
        
        study of crystal structures
      - Gamma rays (Ɣ rays)
        
        Uses
        
        Medical treatment (treatment of cancer by killing cells
- - - - Kilowatt x hour (kWh)
  - - - Overloading causes the main wire to be very hot
        and may even cause a fire.
        
        Use one device per socket, never overload a socket
    - - If a person touches a frayed wire, the high voltage
        can cause a current flows through the body.
        
        Replace old frayed wires
    - - Water may reduce the natural resistance of the
        hand to cause an electrocution.
        
        Dry your hands before handling electrical circuits
    - - Short-circuits may cause a large current to flow
        through, leading to fires.
        
        Call a licensed electrician to fix things
  - - - Neutral wire
        
        Blue
        
        set at 0 volts
        
        completes the circuit by providing a returning path to the supply
      - Earth wire
        
        Brown and yellow
        
        low resistance wire connected to metal casings of appliances
        
        without earth wire:
        
        current will leak to the metal casing
        
        anyone that touches the metal casing gets electrocuted
        
        with earth wire:
        
        current will flow to the earth
        
        reducing electrical shocks when there is a short circuit between the live wire to the metal casing
        
        allows excess current to flow to the earth if there is a leakage of current
        
        allows excess current to flow to the earth if there is a leakage of current
        
        not needed in appliances with plastic casing
      - Live wire
        
        Brown/Red
        
        It is the one that delivers the electric current to the appliance
        
        connected to high voltage
        
        fuse and switch is fitted to the live wire
    - - ELCB (Earth Leakage Circuit Breaker)
        
        trips if there is an unbalanced current (>30 MA) in the live and neutral wire
        
        can trip when there is a current leakage through the earth wire, there is an unbalance of current, causing the ELCB to trip
      - MCB (Mini Circuit Breakers)
        
        trips if there is a current that is above the rated value (e.g. 6A, 20A)
        
        can trip due to overloading
    - - breaks circuit when there is an excessive flow of electric current
        
        does so by putting a thin wire, which melts if there is too much current
      - rating must be slightly higher than the current an electric appliance would use under normal conditions
      - connected to the live wire
      - Typical fuse ratings are: 1A, 2A, 3A, 5A, 10A, and 13A
  - - - Once the energy is used, the source of the energy can be replenished naturally
    - - Once the energy is used, the source of the energy cannot be replenished naturally at a sustainable rate
    - - Geothermal energy
        
        uses
        
        heating
        
        generating electricity
        
        environmental effects
        
        gas poisoning due to the Hydrogen sulfide gas
        
        energy conversion
        
        Earth’s heat energy --> K.E. of steam --> K.E. of turbine --> Electrical
        
        done with a generator
      - Biofuels
        
        uses
        
        fuel for vehicles
        
        environmental effects
        
        Agriculture produce directed to biofuels, resulting in food shortage
        
        energy conversion
      - Nuclear Energy
        
        uses
        
        generating electricity
        
        environmental effects
        
        If a radioactive fallout happens, large areas would be deserted
        
        storage of nuclear energy waste poses a problem to the underground water table
        
        energy conversion
        
        reactor's heat energy --> K.E. of steam --> K.E. of turbine --> electrical
      - Fossil fuels
        
        environmental effects
        
        pollution of the air, leading to upper respiratory illness
        
        increase in carbon dioxide contributes to global warming
        
        uses
        
        generating electricity
        
        fuel for vehicles
        
        energy conversion
        
        Combustion of fuel --> Heat energy
        --> K.E. of steam --> Electrical
      - Solar energy
        
        environmental effects
        
        large tracks of land is needed to house the solar panels
        
        waste solar panels pollute the environment
        
        uses
        
        electricity generating
        
        energy conversion
        
        radiation energy --> electrical energy
        
        done with photovoltaic cells
      - Wind energy
        
        environmental effects
        
        noise pollution
        
        large tracks of land or see needed
        
        uses
        
        electricity generating
        
        energy conversion
      - Tidal energy
        
        environmental effects
        
        affects the marine ecosystem on the seabed due to the structures
        
        uses
        
        electricity generating
        
        energy conversion
        
        K.E. of wind, waves, tides, water
        --> K.E. of turbine --> Electrical
      - Hydroelectric power
        
        environmental effects
        
        affects the terrestrial eco-system
        
        large tracks of land will be flooded, causing a huge displacement of animals and people
        
        uses
        
        electricity gernating
        
        energy conversion
- - - - Potential Difference
        
        V(E) = V1 + V2
        
        The current flowing through each bulb is the same
        
        The sum of p.d. of the bulb is the e.m.f. of the battery
        
        The light bulbs shine with the same brightness
    - - Current
        
        I = I1 + I2
        
        The potential difference of each bulb is equal to the e.m.f. of the battery
  - - - Work done per unit charge
      - Measured in Volts
    - - Work done to drive a unit charge through a component
      - Measured in volts
    - - the rate of flow of positive charges
      - Measured in Ampere
    - - a measure of the opposition an electric current experiences when it flows through the component.
      - Measured in Oms
    - - Amount of current passing through in 1 second
      - Measured in Culoumbs
  - - - Parallel Circuit
        
        R(TOTAL) = (R1^-1 + R2^ -1 + R3^ -1)^-1
      - Series Circuit
        
        R(TOTAL) = R1 + R2 + R3
    - - Variable resistors
        
        Resistance can be varied
      - Fixed resistors
        
        Resistance is fixed
      - Ohmic resistors
        
        They obey Ohm's law and the resistance remains constant under steady physical conditions
      - Non-ohmic resistors
        
        Does not follow Ohm's law and the resistance can vary, as the I/V graphs are not a straight line
- - - - Luminous objects emit light
      - Non-luminous objects do not reflect light
        
        some reflect light
        
        Some absorb light
  - - - Forms shadows
    - - At the point of incidence ( P ), the incident ray, the normal, and the reflected ray all lie in the same plane.
      - The angle of incidence ( i ) is equal to the angle of reflection ( r ).
      - all surfaces reflect light