Main Points - Domestic Energy

• Mains electricity = The electricity supplied to homes, offices and factories
• UK Mains Supply:

  -Alternating Current

  -Voltage of 230V

  -Frequency 50Hz
• Material of wire = Copper
• Wires are made out of copper because it is a good conductor of electrical current
• Material of wire casing = plastic/rubber
• Wire casing is made from plastic/rubber because it is a poor conductor of electrical current (good insulator)
• The live wire is brown
• The neutral wire is blue
• The earth wire is yellow and green
• The dangers of mains electricity:

  • Electrical fires
  • Electrocution
• • Electrical fires occur when a high current flows through a cable or appliance.
  • A fuse or circuit breaker is used to limit the current to a safe level
• Electrocution occurs when contact is made with the live wire (current = above 1000mA).The earth wire can prevent electrocution
• A fuse is a device that is used to protect devices from high currents
• A fuse is a length of wire which melts when the current flowing through it surpasses a certain level. This breaks the circuit
• The earth wire is connected to the metal casing and a metal plate underground. If there is an electrical fault, the current will flow through the metal casing, through the Earth Wire, and to the ground
• Every electrical device in your home will have a power rating
• The power rating is how many Joules of energy a device transforms every second
• If an appliance transfers more energy per second it is more powerful. We can use the power rating to calculate the total amount of energy transferred when the electrical device is being used
• The national grid = A system of transformers and cables
• The national grid:

  -Power stations (25000V)

  -Step-up transformer(25000V - 400000V)

  -Pylons (400000V)

  -Step-down transformer (400000V - 33000V)

  -Distribution lines (33000V)

  -Step-down transformer (33000V - 230V)

  -Underground cables (230V)

  -Homes
• Step up transformer:

  -Power is constant

  -Voltage increases

  -Current decreases

  -Decrease wastage = Increase efficiency

  -Resistance decreases = Less energy loss via the cables as heat
• Step-Down Transformers:

  -Power is constant

  -Voltage decreases

  -Current increases

  -Safer for domestic use

  -More wasted energy
• Direct current = an electrical current that flows in only one direction
• Alternating current = an electrical current which constantly changes direction
• A cathode ray oscilloscope = a device that can show a graph of how an electrical potential difference varies over time
• Positive values on the y-axis show the current going in one direction
• Negative values on the y-axis show the current going in the other direction
• Electrical conductor = a material that allows electricity to flow through it.
• Electrical insulator = a material which does not allow electrical charge to flow through them
• Atoms are neutral particles
• When atoms lose or gain electrons they become charged particles which are called ions
• Objects that are charged affect other objects using the non contact forces of static electricity
• same charge = repel
• opposite charges = attract