Electricity

• current - rate of flow of charge measured in amps using an ammeter - connected in series
• voltage - amount of energy transferred per unit of charge in volts using a voltmeter - connected in parallel
• resistance - opposition to current measured in ohms - can be increased by adding resistance
• in series: current is the same at any point

  in parallel: current is split
• in series: voltage is split

  in parallel: voltage is the same
• series pros and cons

  everything controlled by one switch, less wires

  if one breaks -> circuit wont work
• parallel pros and cons

  can be individually controlled

  more complicated because more wires

  harder to control if components need different voltage
• IV graphs

  fixed resistors and wires: directly proportional

  filament lamp: s shape

  diodes: exponential graph but resides at 0
• explained filament lamp:

  at a higher temperature the atoms in the lattice vibrate more. this causes the resistance to increase as it becomes more difficult for free electrons to pass through
• thermistors - rectangle with hockey stick

  low temperature - high resistance

  high temperature - low resistance
• LDR - light dependent resistors

  more light - lower resistance

  less light - higher resistance
• LED's and diodes can indicate the presence of a current
• power: the rate of energy transfer measured in watts
• fuses - cut flow of electricity if current is to large

  wire heats and melts -> breaking the circuit
• environments that cause electrical damage and can be dangerous

  damaged insulation - touching exposed wire could be lethal

  damp conditions - can cause a short circuit
• electrical safety

  double insulations

  earthing

  fuses

  circuit breakers
• double insulation - non metallic case
• earthing

  if metal cases - a live wire can come into contact and if you touch the electrified case -> electrocuted

  earth wire - provides a low resistance path to the earth

  causes a surge of current in live wire and earth wire. breaks the fuse.
• blue wire - neutral -- left

  Green and yellow wire - earth -- centre

  brown wire - live -- right with fuse
• circuit breakers - automatic electromagnet switch that breaks the circuit if current exceeds a certain value - can be reset.
• energy is transferred as a result of collisions between electrons and lattice of atoms

  when electrons collide, lose some energy by giving it to the ions, vibrate more.

  metal heats up can be used in cooking.
• direct current: constantly flowing in one direction. positive to negative.

  fixed positive terminal and fixed negative terminal

  electric cells or batteries
• alternating current: always changes direction.

  2 identical terminals that switch between positive and negative.

  mains electricity