Physics

Physics

1. Lesson 3 - Specific Latent Heat

   • Definition = Amount of energy needed to change state of 1 kg of a material
   • Energy = Mass X Specific Latent Heat
     • Joules (J) = Specific Latent Heat (SHC) X Temperature change (c)
   • Specific Latent Heat = Energy divided by Mass
   • On a diagram, the flat bits still have heat energy going in to them but the temperature isn't changing because the energy is being used to break intermolecular bonds between the atoms, to allow them to change state.
     • The energy is NOT raising the kinetic energy of the atoms.

2. Lesson 1 - Temperature VS Heat

   • The heat energy travels from the hand, in to the ice cube, so the hand gets colder with less heat energy but the ice melts as there's more heat energy in it.
   • Thermograms are pictures in which colour is used to represent temperature.
     • Hotter areas = White and Red
     • Colder areas = Blue and Green

3. Lesson 2 - Specific Heat Capacity

   • Definition = The amount of energy (heat) that 1kg of a specific material needs to increase it's temperature by 1C
   • Energy = mass X SHC X temperature change
   • SHC = energy -------- Mass X temp change

4. Lesson 4/5 - Transfering Heat

   • Conduction
     • Absorbs heat easily and maintains it.
     • Works in sold, mainly metal.
     • We can stop it by insulating so particles don't pass on vibrations.
   • Convection
     • Gas heated expands and rises, then gets cool and drops then the process continues.
     • Works in gases and liquids
       • We can stop convection by trapping particles in pockets.
   • Radiation
     • Energy radiates waves. It is then absorbed by surfaces to make them warmer.
     • Works in solids, liquids and gases.
     • We can stop radiation by reflecting back waves

5. Lesson 6 - The cost of saving energy

   • Efficiency of a heating system tells you how much of the energy you put in actually comes out as heat energy.
     • Efficiency = useful energy out --------------- useful energy in
       • X100 for percentage
   • Some energy saving methods cost a lot to install in the first place. You can work out their payback time by dividing their cost by the amount of money they save each year.

6. Lesson 7 - Electromagnetic Spectrum

   • Red Orange Yellow Green Blue Indigo Violet
   • Low Frequency ||||||||||||| High Frequency
   • Light Spectrum = If you divide light up in to all its different frequencies, you get a rainbow, this is called a spectrum. Actually the spectrum goes a lot further than visible light. There are waves on both sides that we can't see
   • Infrared - Security lights burglar alarms remote controls
     • Microwave - Heating food Communications
       • Radio - communication Television/radio
         • Visible - CD Disks Optical Fibres Photography
           • Ultraviolet - Sun rays Checking forgeries
             • Xray - Image bones view internal structures
               • Gamma Ray - Kills cancer cells Kills harmful bacteria sterilising medical equipment
                 • Grandmas
               • X-rays
             • Use
           • Very
         • Recipes
       • Magic
     • Important

7. Lesson 8 - Waves

   • Transfers energy without transferring matter.
     • Frequency, F (In hertz): The number of complete waves passing a point each second.
     • Transverse waves move at 90 degree to wave flow.
       • Speed( C) = Frequency (F) X wavelength.
         • Wave Length= Speed ---------- Frequency
   • Transverese- Light and water Longitudinal - sound
     • Transverse - movement of individuals go side to side Longitudinal - movement of individuals go forward and back
       • Refraction- When light goes from a less dense material e.g. air to a dense material e.g glass then the ray bends the normal. Light travels slower through glass.
         • Diffraction- When water waves pass through a gap, the waves spread out. This is called diffraction. For maximum diffraction, the gaps should be the same size as the wavelength.