Domestic Electricity

• ELECTRICAL POWER - What is the Unit of Power - Watts
• ELECTRICAL POWER - Equation that relates time And power -

  Energy transferred = power x time
• ELECTRICAL POWER - Equation to calculating the power in an electrical circuit-

  Power = Voltage x Current
• ELECTRICAL POWER - Equation for power IN SYMBOLS -

  E = P x t - Energy transferred = power x time
• ELECTRICAL POWER - Equation for power IN SYMBOLS -

  P = V x I - Power = Voltage x Current
• Triangle Equations

  
• ELECTRICAL USE IN THE HOME - How can you reduce energy usage in your homes ?

  • Turn off lights
  • short showers
  • shower instead of baths
  • Turn off devices fully
• FORMULA - Work out the number of units

  UNITS USED = POWER x TIME

  (kWh) ( kw) (h)
• FORMULA - Calculate the total cost

  COST = UNITS USED x COST PER UNIT
• Is it Joule, Jewl or Juels?

  Joule
• HOW WE CAN REDUCE OUR ELECTRICITY BILLS ?

  Produce your own electricity
• Rooftop photovoltaic cell = solar panels
• Micro-generation of electricity MEANS generating electricity locally on a small scale and close to where it is needed.
• MICRO-GENERATION OF ELECTRICITY - examples

  • rooftop photovoltaic cell
  • domestic wind turbines
• Rooftop photovoltaic cells - ADVANTAGES

  • Easy to maintain
  • Reduces cost of energy bills
  • Renewable energy source
  • Increase house value
  • Can be used to power homes
  • Pollution free
• Rooftop photovoltaic cells - DISADVANTAGES

  • Don‘t work for every type of roof
  • High initial cost of material and installation
  • Depends on the weather
  • Difficult to find a local installer
• Domestic wind turbines - ADVANTAGES

  • Create clean energy without producing any emission that could cause any damage to the environment
  • Capturing power from the wind
  • Renewable energy source
  • Qualify for tax incentives at local national level
• Domestic wind turbines - DISADVANTAGES

  • BLADES CAN KILL BIRDS
• TYPES OF CURRENT - AC/DC

  Alternative Current (AC)

  • current is constantly changing around the circuit
  • UK’s main supply is Ac at 230V and a frequency of 50Hz

  
• TYPES OF CURRENTS - AC/DC - Direct Current (DC)

  • Current flows in single direction around a circuit
  • Batteries are examples of DC sources

  
• TYPES OF CURRENTS - AC - Devices which use AC supplies

  • Television
  • Kettle
  • Microwave
  • ( anything using mains electricity )
• TYOES IF CURRENTS - DC - Devices which use DC supplies below

  • Mobile phone
  • Laptop
  • Direct
  • ( devices which run on batteries )
• PLUGS IN HOME

  
• PLUGS IN HOMES - Earth wire - yellow + green - carry current away from device
• PLUGS IN HOMES - Live wire - Brown - carries current to the device
• PLUGS IN HOMES - neutral wire - blue - connects to the cable in the wall and completes the circuit
• PLUGS IN HOMES - Fuse - Glass or Ceramic canister - melts if the current gets too high
• PLUGS IN HOMES - Other Insulation - there is extra plastic insulation wrapped around them all for safety
• PLUGS IN HOMES - Cable grip - holds cables tight in place so wires don’t become loose
• * The cables can be made thinner because there are 2 paths for the current
• * Each part of the cable carries less current because the current flows both ways
• * A ring main circuit is more convenient since sockets can be placed anywhere on the ring
• * Each socket has 230V and they can be operated separately
• CIRCUIT BREAKERS -

  • These are automatic switches that act similar to a fuse.
  • They break the circuit when there is a fault
  • They break the circuit by use of an electromagnetic switch that pulls a trip bar when excess current flows
• CIRCUIT BREAKERS

  
• Type of circuit breakers - MINIATURE CIRCUIT BREAKERS (MCB)

  • can be reset
  • uses an electromagnet to open a switch if the current goes above a certain value
  • switches off the current faster than a fuse
• Type of circuit breakers - RESIDUAL CURRENT CIRCUIT BREAKERS (RCCB)

  • switches off the circuit when there’s a difference between the currents in the live and neutral wires of the appliance
  • More sensitive than MCBs
• SUMMARY OF ELECTRICAL SAFETY DEVICES - Fuse -

  • HOW - melts if too much current flows
  • ADVANTAGES - Prevents overheating
  • DISADVANTAGES - has to be replaced once it has blown
• SUMMARY OF ELECTRICAL SAFETY DEVICES - MCB

  • HOW - switches off circuit if too much current flows
  • ADVANTAGES - can be reset and reacts faster than a fuse
  • + Prevents overheating
  • DISADVANTAGES - more expensive than a fuse
• SUMMARY OF ELECTRICAL SAFETY DEVICES - RCCB

  • HOW - detects a difference in the current of the live wire and neutral wire + switches of the circuit
  • ADVANTAGES - more sensitive than MCB can be reset
  • DISADVANTAGES - may still get an electric shock (smaller)