physics

• energy in a system cannot be created or destroyed but transferred or stored in different ways.
• mechanical work- a force moving an object through a distance.
• electrical work- charges moving due to potential difference.
• heating- temperature differences causes electrically or chemically charged reactions
• radiation- energy transferred as a wave (e.g the sun emits light/ infrared radiation)
• energy transferred- work done (J)= force (N) x distance (M)
• kinetic energy- 1/2 x mass (kg) x velocity 2 (m/s)
• GPE- GPE (J) = mass (kg) x gravity (10N/kg) x height (m)
• dissipation- ways energy is wasted
• 3 examples of non- renewable: oil, coal, gas

  3 examples of renewable: wind, solar, geothermal
• process of power plant:

  1. fuel burnt in boiler- chemical energy store converted to thermal energy store.
  2. boiler heats water turns to steam
  3. steam turns turbines
  4. turbines turn generators
  5. electricity is generated by generator
  6. electricity transported around country (National Grid)
• step up transformer- more turns on primary coil and less on secondary coil
• step down transformer- more turns on secondary coil and less on primary coil
• charge- charge (Q) = current (I) x time (seconds)
• potential difference- PD (V) = energy (E) / charge (Q)
• resistance (Olmn's law)- PD (V)= current (I) x resistance (R)
• components of a circuit:

  1. cell
  2. battery
  3. open/ closed switch
  4. filament bulb
  5. fixed resistor
  6. variable resistor
  7. voltmeter
  8. ammeter
  9. fuse
  10. diode
  11. LED
  12. LDR
  13. thermistor
• what does:

  1. open switch- electricity cannot flow through
  2. closed switch- electricity can flow through
  3. diode- current flows in specific directions
  4. resistor- slows the flow of current
  5. fuse- helps regulate electricity of overheats
  6. thermistor- affected by heat
  7. cell- electrical power that provides energy
  8. battery- main source of energy, provides voltage
  9. variable resistor- electric resistance can be adjusted
• ohmic conductors- current through a resistor is directly proportional to the PD across it
• resistor on a graph- current through a resistor is directly proportional to the PD across it.

  
• lamp on a graph- the filament in the bulb heats, resistance increases

  
• diode on a graph- resistance is so high it does not go past 0

  
• LDR on a graph- resistor increases with light intensity

  
• thermistor on a graph- as temp increases, resistance decreases

  
• delocalised- not attached to a specific atom
• series circuit- current is always the same

  parallel- current is shared
• series rules:

  1.     Same current passes through components.

  2.    Total PD is different between components.

  3.    Total resistance of components is the sum of resistance in each component.
• parallel rules:

  1.     Current is split across parallel branches.

  2.    PD across each branch is the same.
• power = PD / current
• changing state:

  melting- solid to a liquid

  freezing- liquid to a solid

  evaporating- liquid to gas

  condensing- gas to liquid
• safety

  Live wire- carries alternating PD from supply (brown)

  Neutral wire- completes circuit (blue)

  Earth wire- safety wire to stop appliance becoming live (yellow/green)
• melting and freezing-

  1. energy transferred to substances causes particles to vibrate rapidly in fixed rows.
  2. particles begin to move from fixed position then melts into a liquid
• evaporating and condensing-

  1. heat transferred to substance increases energy of particles. makes particles vibrate and move freely.
  2. particles escape from liquid freely. particles evaporate, turning to a liquid
• physical change on a graph-

  Temperature increases= melting

  Staying still for a long period= boiling

  increasing into higher temperatures= gas

  Going into negative numbers= solid
• solids-

  fixed shape and volume

  cannot flow

  cannot be compressed
• liquids-

  fixed volume

  no fixed shape

  move freely

  cannot be compressed
• gas-

  no fixed shape/ volume

  can flow

  can be compressed
• internal energy- total amount of kinetic energy and chemical potential energy of all the particles in the system.
• when energy is raised in temp, particles speed up (kinetic energy)
• substance melts/ boils energy put into breaking bonds (increases potential energy)