Electricity

• EQUATIONS

  • Queen Ivy tried very interesting roads
  • praying in Vivienne post in SQUARE reality.
  • Emily prayed to eradicate queen Vivienne
• Total resistance is the sum of all the resistors in a circuit
• Symbols:

  • A: switch (open or closed)
  • B: lamp
  • C: fuse
  • D: cell
  • E: battery
  • F: diode
  • G: resistor
  • H: voltmeter
  • I: ammeter
  • J: variable resistor
  • K: thermistor
  • L: LED

  
• For charge to flow:

  • circuit must be closed (no open switches)
  • there must be a source of potential difference / voltage (battery or cell)
• Current: flow of electrical charge

  • greater rate of flow of charge = greater current
• In a single closed loop, current has same value at any point

  Current through component depends on resistance of component

  • greater resistance = small current for given voltage of component
• CHARGE: Causes a force when near another charge

  • unlike attract and alike repel
• CURRENT: Flow of electrical charge

  • greater flow of charge = greater current
• VOLTAGE: electrical push of energy

  • greater voltage = greater current
• RESISTANCE: Atoms vibrating, resisting the flow of electrons

  • greater resistance = less current
• CURRENT - VOLTAGE GRAPHS:

  Resistor at a constant temperature:

  • constant = ohmic conductor
  • linear graph
  • constant value is the resistance

  Lamp:

  • non-ohmic conductor
  • non-linear graph
  • resistance increases as temperature of lamp increases

  Diode:

  • non-ohmic conductor
  • non-linear graph
  • current through diode only flows one way

  
• CURRENT - VOLTAGE GRAPHS:

  X - Diode

  Y: Resistor

  Z: Lamp

  
• THERMISTOR

  • as temperature increases, resistance decreases (used in thermostats)

  LDR (light)

  • as intensity of light increases, resistance decreases (used in street lights)

  WIRES (length)

  • as length increases, resistance increases and current decreases (therefore shorter wires are more powerful)
• SERIES CIRCUIT:

  • closed circuit
  • current is the same , follows single path
  • resistance is sum of each resistor (R1 + R2 etc)
  • voltage is shared: voltage of power supply = sum of voltage in each component

  PARALLEL CIRCUIT:

  • branched circuit
  • current is shared: current of power supply = sum of current in each component
  • voltage is the same
  • resistance is 1/R1 + 1/R2

  
• Kinetic energy is used in motors

  Thermal energy is used in kettles
• INSULATORS: electrons can’t flow, they are fixed

  CONDUCTORS: electrons CAN flow, they are delocalised
• 2 insulators are rubbed:

  • friction between both transfers electrons between each object, electrons have been lost
  • objects can’t gain transferred electrons to balance as electrons can‘t flow through insulators
  • object rubbing other object is NEGATIVELY charged, object getting rubbed is POSITIVELY charged
• 2 conductors are rubbed:

  • friction between both transfers electrons between each object, electrons have been lost
  • objects gain transferred electrons to balance as electrons flow through conductors and cancels out
  • 2 neutral objects
• SPARKING:

  • occurs when enough charge is built up & objects are close but not touching
  • spark happens when charge jumps through air from highly negative object to highly positive object to cancel
  • FORCE EXERTED: electrostatic force (higher charge or closer together = higher force)
• ELECTRIC FIELDS:

  • Point in the direction a positive charge would go (away from positive and towards negative)
  • Stronger charge = more field lines , stronger force