Electric current, circuits

1
Electric current, circuits

• Electric current
• under influence of the electric field, mobile
  charges will move towards positions of lower
  potential energy
• positive charges will move toward lower
  potential, negative charges toward higher
  potential
• a conductor is a material which has mobile
  charges
• when a potential difference is maintained between
  the ends of a conductor, charges will move ?
  electric current flows
• Current
• electric current ordered flow of electric
  charge, rate at which charge moves past a
  reference point I ?q/?t
• unit of current 1 Ampère 1A 1
  Coulomb/second
• potential difference (voltage) can be maintained
  by battery or other voltage source (often
  referred to as power source)
• electric circuit
• assembly of conductors, voltage sources and
  other circuit elements
• Ohm's law
• relates the current to the applied voltage I
  V/R, V I R current voltage /
  resistance,

2
Resistance, power

• where resistance is a measure for the
  opposition against charge flow within the
  conducting material (e.g. due to collisions with
  atoms, other charge carriers,..)
• unit of resistance 1 ohm 1 ? 1 V/A
• due to resistance, not all electric potential
  energy is converted into kinetic energy of charge
  carriers and eventually useful work - some (or
  all) of it is dissipated as heat
• power consumption in a circuit
• when current is allowed to flow, charges move
  from higher potential energy to lower potential
  energy
• total change in potential energy amount of
  charge moved x voltage ?q V
• this change in potential energy can be used to do
  work and/or is converted into heat.
• loss in potential energy has to be made up by
  energy supplied from the power source
• power P (energy converted) / time ? q V
  /?t V (?q/?t) V I
• power current x voltage
  
• under the influence of a voltage (? electric
  field) applied across a conducting medium, a
  current (of positive charges) flows from higher
  to lower voltage. The potential energy lost by
  the charges is converted into work and/or heat,
  and has to be replenished by the power source.