current

• current = charge / time
• what is current?


  the rate of flow of charge, an electric current is carried by a flow of electrons

  electrons carry negative charge

  the amount of charge passing through a point in a circuit per unit time
• what is the unit for current?

  'ampere' (A)

  1 ampere = 1 coulomb per second
• current calculation 


  Q=I x t

  Q = charge/coulombs

  I = current/amps

  t = time/seconds
• direct current 


  direct potential differences produce direct currents

  direct currents always flow in the same direction (polarity)
• alternating current


  alternating potential differences produce alternating currents

  alternating currents change direction (polarity)
• an ammeter measures current in amps
• ammeters must be placed in series
• the greater the resistance, the smaller the current that flows through it for a given potential difference across the component