Series and Parallel Circuits

• Defining characteristic of a series circuit

  there is only one path for electrons to flow
• Defining characteristic of a parallel circuit

  there is more than one path for electrons to flow, each of which is called a branch

  all components are connected between the same electrically common points
• Series connection

  components are connected end-to-end in a line to form a single path for electrons to flow
• Parallel connection

  all components are connected across each other's leads
• In a purely parallel circuit, there are never more than two sets of electrically common points, no matter how many components are connected
• What is true of series circuits? and Why?

  the amount of current is the same through any component in the circuit; this is because there is only one path for electrons to flow in a series circuit due to the fact that free electrons flow through conductors like marbles in a tube (thus, the rate of flow at any point in the circuit at any specific point in time must be equal)
• Caveat to Ohm's Law for Series and Parallel Circuits

  all quantities (voltage, current, resistance, power) must relate to each other in terms of the same two points in a circuit
• There are three principles for series circuits:

  1. all components share the same current
  2. resistances add to equal a larger total resistance
  3. voltage drops add to equal a larger total voltage
• You should only apply Ohm's Law to the values within each vertical column
• Explain the first principle of parallel circuits

  the voltage is equal across all components in the circuit

  this is because there are only two sets of electrically common points in the circuit, and voltage between sets of common points must always be the same at any given time
• In parallel circuits, the total current must equal the sum of all individual (branch) currents. As the total current exits the negative batter terminal and travels through the circuit, some of the current splits off to go through each branch
• Parallel circuit definition

  a circuit where all components are connected between the same set of electrically common points (all components are connected across each other's terminals)
• There are three principles of parallel circuits:

  1. all components share the same voltage
  2. resistances diminish to equal a smaller, total resistance
  3. branch currents add to equal a larger, total current
• resistance

  the measure of friction a component presents to the flow of electrons through it; symbolized by "R" and has units of ohms
• Conductance

  the reverse of resistance; how easy it is for electrons to flow

  G = 1/R

  has symbol of "G" and units of "siemens"
• The greater the resistance, the less the conductance
• How does multiple paths for current impact total resistance in a parallel circuit?

  It reduces total resistance in the circuit because electrons are able to flow easier through the whole network of multiple branches than any one of the branch resistances alone
• Parallel resistors resist less together than they would separately
• Total parallel conductance is greater than any of the individual branch conductances because parallel resistors conduct better together than they would separately
• Power

  measure of rate of work

  P=IE, P=E^2/R, P=I^2R

  total power is additive for any configuration of circuit
• Since power dissipated must equal the total power applied by the source(s), circuit configuration has NO effect on the math