Electric current

• William Gilbert


  English scientist who wrote 'De Magnete', distinguishing the lodestone effect from static electricity produced by rubbing amber
• Hugh Williamson reported experiments on electric shocks from electric eels, John Hunter described the structure of the fish's electric organs


  1775
• Luigi Galvani published discovery of bioelectromagnetics, demonstrating electricity as the medium for neurons to pass signals to muscles


  1791
• Static electricity


  Electric shock caused by buildup of electrons
• Static electricity


  • Small amounts cause slight shocks like when rubbing feet on carpet
  • Large amounts can discharge as lightning
• Static electricity


  Stationary or collects on surface of object
• Current electricity


  Flowing rapidly through a conductor
• Static electricity


  Lacks electrical pressure/voltage, unlike current electricity which has flow from high to low voltage
• Electric current


  Movement of electrons from one place to another
• Electric current


  Measured in amperes
• Closed circuit


  Electrons can only follow a complete, unbroken path
• Open circuit


  Incomplete path, no current flow
• Switch


  Closes circuit to allow current flow, opens circuit to stop current flow
• Conductor


  Material electricity passes through easily (e.g. metals)
• Insulator


  Material electricity does not pass through easily (e.g. rubber, plastic)
• Resistance


  Measure of how easy/hard it is for electric current to move through a material, measured in Ohms
• Resistance


  • Depends on material, length, and thickness of wire
  • Causes electrical energy to turn into heat and light energy
• Electromotive force


  The "push" that keeps current flowing, measured in volts
• Higher voltage


  Electrons have more energy to do work
• Batteries


  Chemical substances that can generate voltage for use in a circuit
• Dry cell battery


  Zinc container with moist chemical paste and carbon rod
• Direct current (DC)


  Current flows in one direction

  
• Alternating current (AC)


  Current changes direction regularly
• Resistance


  Opposition to flow of electric current, causing conversion to thermal or light energy
• Ohm's Law


  Relationship between resistance, current, and voltage: R=V/I

  
• Series circuit


  Single pathway for current flow, all devices fail if circuit breaks
• Parallel circuit


  Multiple pathways for current flow, devices may continue working if one path breaks
• Electrical power


  Product of current and voltage, measured in Watts
• Determining electrical energy


  Electrical energy = power x time

  
• Fuse


  Melts to break circuit if wire gets too hot

  
• Circuit breaker


  Switch-like device that can be reset after circuit repaired
• Watt


  Unit to measure electric power
• Kilowatt-hour


  Unit to measure amount of electrical energy used

  
• Direct current (DC)


  Unidirectional current flow

  
• Alternating current (AC)


  Bidirectional current flow
• Pulsed current (PC)


  Unidirectional or bidirectional flow that periodically ceases
• Electric current


  Flow of electric charges (electron beam in metal or ions in electrolyte), measured in amperes
• Direct Current (DC)


  Unidirectional current that flows continuously over time
• Alternating Current (AC)


  Bidirectional current that flows continuously over time
• Direct current is characterized by a constant return and direction of flow of electric charges, as opposed to alternating current