Transcript Class Notes/Mr. Heer`s Powerpoint

Series and Parallel
Circuits
Series Circuits
Series Circuit: A circuit in which all the
current travels through all devices. One pathway.
Current through all devices is the same.
Voltage adds up.
Equivalence Resistance: The resistance with which all resistors can be thought of as.
After equivalence resistance is found, the current flowing through the circuit can be
found with the equation V = IR.
Voltage Divider: Series circuits are thought of as voltage dividers. They can produce a
voltage of desired magnitude.
Parallel Circuits
Parallel Circuits: A circuit where there are several
current paths. Circuit that has a junction.
Voltage across all devices in parallel is the same.
Current adds up.
Find the total current in the circuit to the left.
Equivalence Resistance of a Parallel Circuit
1
1
1
1
 

 
RT R1 R2 R3
Applications of Circuits
Short Circuit: When you bypass the load, lowering the resistance to almost nothing,
which skyrockets the current to almost infinity.
Fuse: A circuit protection device that melts if the current is too high.
Circuit Breaker: A circuit protection device that opens automatically if the current is big
Ground Fault Interrupter: A personal protection device that is built into some outlets
that cuts power to the outlet if it senses current is going not to the load. (ie you)
Combination Circuits
Combination Circuit: A circuit that has loads in both series and parallel.
How to Solve Combination Circuits:
1) Draw a schematic
2) Find any parallel loads. Calculate their equivalent resistance with 1  1  1  1    
RT R1 R2 R3
Draw a new schematic with one resistor with the new value.
3) Find any resistor in series. Calculate their equivalent resistance by adding. Draw a
new schematic with a new resistor with that value.
4) Repeat steps 2 and 3 until you are left with ONE resistor. That is the equivalent
resistance
5) Use the equation V = IR
to find the total current.
6) Remember that if any loads are in parallel, their voltage is the same (the current
splits) and if any loads are in series, the current is the same (their voltages add)