Series and Parallel Circuits

1
Series and Parallel Circuits

• Series circuits
• Parallel circuits
• Series-parallel circuits

2
Series circuits

• A circuit that has more than one load and all
  current flows through all the loads in the
  circuit
• Series circuits used in an automobile
• Blower circuit where variable fan speeds are
  required
• Seat heaters using a variable resistor to control
  temperature

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Example of a series circuit for a blower motor
4
Series circuits

• Total of all voltage drops will equal the source
  voltage
• Voltage drop is proportional to resistance
• The higher the resistance, the greater the
  voltage drop
• As resistance increases, current flow decreases

5
Parallel circuits

• A complete circuit with more than one path for
  current to flow
• Current flowing into each branch or leg varies
  according to the amount of resistance in that
  branch of the circuit
• The current flowing into any junction of an
  electrical circuit is equal to the current
  flowing out of that junction

6
Parallel circuits

• The total resistance of a parallel circuit is
  always less than that of the smallest resistance
  of any branch of the entire circuit
• The voltage is the same for each branch of the
  parallel circuit
• The sum of the individual currents in each leg
  will equal the total current

7
Parallel circuits

• Most of the current flow in a parallel circuit
  will occur in the branch with the least
  resistance
• As long as other branches of the circuit are
  complete, current will flow through them in
  accordance with Ohms law
• The only place where electricity can take the
  path of least resistance is in a series circuit
• Most lighting circuits on automobiles are
  parallel circuits

8
Series-parallel circuits

• Includes both parallel loads and loads that are
  electrically connected in series
• Added resistance in series portion of circuit,
  will decrease current flow through parallel
  branches evenly
• Example of series-parallel circuit used in
  automotive applications dash board illumination
  with a dimmer switch
• As resistance increases with variable resistor in
  dimmer switch current flow is decreased through
  dash lights