LESSON 04 – PARALLEL CIRCUITS

 

 

LESSON NOTE

PARALLEL CIRCUITS

 

A parallel circuit is a circuit that contains more than one path for the current to flow through.  However, each path or branch contains only one load.  Therefore, no electron travels through two loads.

 

Example:

 

We will call each path option a branch.

 

 

PROPERTIES OF PARALLEL CIRCUITS

 

The current is not constant throughout the circuit. When electrons arrive at a fork in the circuit, some will go one way while others will go the other way. 

The voltage drop in each branch will be the same.

 

For each branch, I x R (voltage drop) is the same. 

    • The branch with the higher R gets less I.
    • The branch with the lower R gets more I.

 

The voltage drop in each branch will be the same as the voltage of the source.

Calculating the resistance over a parallel circuit requires the use of a formula:

 

RT = (1/R1 + 1/R2 + 1/R3 + …)-1

 

Note that it is best to keep a high level of precision until the final answer.  It is probably best to convert fractions to decimal values.  Use a calculator!

 

SIMPLE CASES

 

If you have two identical resistors in parallel, the total resistance of the parallel circuit will be half of what an individual resistor is.

If you have three identical resistors in parallel (three branches), the total resistance of the parallel circuit will be one third of what an individual resistor is.

 

And so on…