P2 - Electricity

• Electrical components diagram

  
• Diode


  Current flows in one direction
• Resistor


  Stops current
• Variable resistor


  Allowing some current through
• Fuse


  Safety (so it doesn't burn)
• LDR


  Responds to light
• Thermistor


  Responds to temperature
• Series circuit


  - All components connected in single line

  - Current the same through every component

  - Potential difference spread across components (one path and cannot go to the battery to recharge)
• Parallel circuit


  - Current divides into two or more paths before combining again

  - Potential difference the same throughout all components(goes back to the battery to get recharged)
• Resistance


  Slows down the current due to the negatively charged electrons coming close to the positive metal ion (nucleus) and being attracted to it.

  V=IR
• Ohm's law


  The current flowing through a resistor at a constant temperature is directly proportional to the potential difference across it.
• Ohm's resistor


  The current is directly proportional to the potential difference and therefore has a positive correlation. The positive correlation isn't affected when the battery is turned around as the current still increases as the potential difference increases. It obeys the Ohm's law.

  
• Filament bulb


  As the potential difference increases, so does the current. The number of collisions between electrons and ions increases so results in a higher resistance and a higher temperature.

  Gradient decreases = resistance increases

  
• Diode graph


  A diode only allows current to flow in one direction so the current will only flow when the battery is one way. This is why on the negative side of the graph the current is level as it isn't flowing. On the positive side of the graph, as current increases, so does the potential difference.

  
• Charge equation


  current x time
• Energy equation


  charge x potential difference

  power x time
• Power equation


  current x potential difference

  current^2 x resistance

  work/time

  energy/time
• Power


  The rate of doing work (Watts)
• Hertz

  Unit of frequency
• Alternating current


  Type of current that is constantly swapping direction. Mains electricity is alternating.

  - Can be converted to a different potential difference easily using a transformer

  - Predominantly powers our electricity today

  - Developed by Nikola Tesla
• Direct current


  Flow of electric charge in one direction only.

  - Developed by Thomas Edison

  - Not easily converted to higher or lower potential differences

  - More stable

  - Computers, LEDs, electric vehicles run on D.C.
• UK plug diagram

  
• Live wire


  Carries the 230V from the supply (Brown)
• Neutral wire


  Completes the mains circuit (Blue)
• Earth wire


  Carries electrical current away if there is a fault (down to earth) (green-yellow)
• Consumer


  The end user of generated electricity
• The National Grid


  A system of cables and transformers linking power stations to consumers.

  
• Underground cables

  + Do not affect views

  + Less affected by bad weather

  - Difficult to repair

  - Expensive
• Overhead cables


  + Easy to repair

  + Cheaper

  - Spoil landscape

  - Affected by bad weather
• Static


  Always causes by electrons being moved from one material to another.

  Electrons removed -> positive

  Electrons added -> negative
• Induced charge


  The balloon has a negative charge and the wall has a neutral charge. As negative charges repel, the electrons in the wall (negative charge) repel from the balloon causing electrons in the balloon to be attracted to the positive charge in the temporary imbalance of charges.

  
• Electrostatic field lines


  Drawn from a proton's point of view. The force is greatest where the lines are closer together. One field is a radial field.