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

3. 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 Ohm’s 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