Physics

• Earthing (earthing metal cases)


  Many electrical appliances have metal cases, posing a potential safety hazard. If the case becomes electrified, anyone who touched it would risk being electrocuted. The earthing wire is an additional wire that comes into contact with the earth (inside the appliances) and creates a safe route for current to flow through in the case of a short circuit, preventing electric shocks.
• Earthing wires


  • Very low resistance
  • Provide a low resistance path to the earth, so if one does come into contact with a current, it flows through the earthing wire instead of the person, giving a safe route to the earth
• The high current through the earthing wire cuts off the supply of electricity to the appliance, making it safe
• Fuses and circuit breaks 


  They are safety devices designed to cut off the flow of electricity to an appliance if the current is too high / large (due to fault or surge).
• Circuit breakers


  Automatic electromagnet switches that break the circuit if the current exceeds a certain value. Main circuit breakers can quickly shut off electricity to the whole house whilst branch circuit breakers can shut off specific areas of the house.
• Circuit breakers vs fuses

  Circuit breakers don't melt/break and can be reset and used again, working much faster than fuses
• Circuit breakers are typically used for the main circuit, while branch circuit breakers shut off specific areas of the house
• Fuses stop the flow of current by melting and breaking if the current becomes too large and heats up the thin metal wire, causing it to break and stop the current. Therefore, protecting sensitive components and people because if the components function at too high temps, it can cause a fire.
• Circuit breakers break the circuit if the current is too high.
• Earthing wires have very low resistance allowing a strong current surges through them which breaks the fuse and disconnects the applianCe.
• What the some common electrical hazards?

  Fray wires (you could get electrocuted), sticking metals into outlets (creates a short circuit), watering plants near electronics (creates short circuits and electrical shocks), damaged insulation (electric shock), cables overheating (causing fires), damp conditions (electrocution and short circuit through the water)
• Domestic appliances contain what safety features to reduce these hazard?

  Double insulation and insulation, earthing, fuses and circuit breakers.
• How many wires are there in a cable?

  three. The live wire (brown coloured wire), the earth wire (green wire which is a safety wire and common in most cables but not all contain it), and the neutral wire (the blue wire). The earth and neutral wire are safe wires and safe to touch. The earth wire protects your from being electrocuted.
• How can electricity be used safely? Do not overload sockets, do not leave plugged items in for 24 hours, check constantly for fray wires, never mix water and electricity, do not stick anything other than a plug in a socket, wires should be plugged correctly and checked for damages.
• A series circuit has only one pathway for charge carriers so they must pass through every component on their way around the circuit. This means that the same amount of charge passes through each resistor in a given time interval.
• In a parallel circuit, the total current splits up at the point where components join the main wire. Each branch carries its own current. So the current flowing through any two points in a parallel circuit will always add up to the total current flowing through the whole circuit.
• In a parallel circuit, the current is different between bulbs, voltage is the same, and power is different.
• In a series circuit, the current is the same between bulbs, voltage is different and power is different.
• What is the formula for resistance?

  Voltage (volts) / Current (amps)

  • through using the o.g formula V= IR
• Voltage is measured in what units?

  Volts
• Current is measured in what units? Amps
• The symbol used for potential difference or voltage is V
• What is the area of a trapezium formula?

  (UB + LB) H / 2
• What is energy transferred also known as?

  Total energy or work
• Energy transferred is measured in what? and how can it be calculated?

  Energy transferred (Joules) = Power (watts) x time (secs)

  Energy transferred = current (amps) x voltage (volts) x time

  Energy transferred = charge (coulombs) x voltage
• Power is measured in what? and what is its formula?

  Power (watts) = current (amps) x time (secs)
• What is the formula for voltage and its units?

  Voltage = current (amps) x resistance (ohms)
• what is the formula and units for charge?

  Charge (coulombs) = current (amps) x time (secs)
• Another word for charge is what?

  Charge transferred (coulombs)
• 1A = 1000mA

  A = current

  mA = millicurrent
• Frequency (Hz) = 1 / time period (secs)
• electricity was discovered for a reason in the 1900's. It was for military usage, to eliminate life. When they are done with the electricity, they would then give it to us. They found that electricity was powerful stuff so they decided to run test trials on inmates as they thought it was okay as they were going to die anyways. This was a very cruel way to test electricity before, now, they use lethal injections.
• When testing electricity on the inmates before, they would press a switch and the inmate would get electrocuted. One guy fainted after recieving the voltage. They continued to try again because a pulse was still detected.
• our inner body is more conductive than the outside.
• Electricity goes through things with less resistance.
• What is inside an electrical cable?

  3 different wires made up of conducting material and insulated by metal or plastic casing. The wires are made up of copper (which is one of the best conductors - good conductor). However, copper is not as expensive as gold. It is cheaper.
• The wires inside an electrical cable are surrounded by plastic (an insulator) which lowers the chance of electrocution.
• In each cable, there are 2 (USA) or 3 (UK/HK) wires depending on the country.
• What are the names of each wire in a electrical cable?

  Live wire, neutral wire, earth wire.
• what does the live wire do?

  The live wire (brown wire) carries a current that alternates between a negative and positive voltage.