Parallel Circuits 8 Note Boxes. Quick Review The electrons that move to make electricity come mostly from the wires in the circuit, not the battery. Metals.

Parallel Circuits

8 Note Boxes

Quick Review

The electrons that move to make electricity come mostly from the wires in

the circuit, not the battery.

Metals are conductors because their electrons

can move.

Box #1

Introduction

There are two network configurations – series and parallel.

Last class we covered a series network. In this lesson we will cover the parallel circuit

and all the methods and laws associated with it.

Do You Remember?

What did we say was the biggest DISADVANTAGE of using a series circuit?

Branching Out

Parallel circuits have independent paths.We call these independent paths “branches”.

Box #2-3 notes

Junctions

Junction: Where the branches join or split

B1

B2

B3

B4

Box #2-Con’t

Parallel Circuit Advantage

In a parallel circuit, each device operates independent of the other devices.

A break in any one path does not interrupt the flow of charge in the other paths.

Box #3

Independent Paths

Which one?

Which switch, if opened, will cause

the light bulb to stop glowing?

Why?

Which circuit is built so that if one light bulb goes out, the other three light bulbs will continue to glow?

Voltage in Parallel Circuits

The batteries are typically in series with one another.The total voltage therefore is found by adding up each

individual battery.The total voltage going across each branch is the same.

Box #4-2 notes

That was Easy…

Now here’s is where things start to change from a series circuit

The total current divides among the parallel branches

Huh? Remember Ohm’s Law?

Box #4-Con’t

Ohms’s Law

(Amps)

(volts)

(ohms)

Comparing and Contrasting Series vs

ParallelIf they’re all in a row (series), you just add them

up and go!

If they have a different road (parallel), take the time to break the code.

Box #5-Technically 2

notes

Current in Parallel Circuits

Resistance in Parallel Circuits

From the battery’s perspective, the overall resistance of the circuit is decreased.

This means the overall resistance of the circuit is less than the resistance of any one of the branches.

Box #6-2 notes

think!What happens to the light intensity of each lamp in a parallel circuit when

more lamps are added in parallel to the circuit?

Resistance in Parallel Circuits

think!What happens to the light intensity of each lamp in a parallel circuit when more lamps are added in parallel to the circuit?

Answer:

The light intensity for each lamp is unchanged as other lamps are introduced (or removed). Although changes of resistance and current occur for the circuit as a whole, no changes occur in any individual branch in the circuit.

Parallel Circuits

Parallel Resistors For resistors in parallel, the total resistance is

determined from

Box #6-Con’t

Ready to rip your hair out yet?

There IS an easier way…

Circuit Overload

To prevent overloading in

circuits, fuses or circuit breakers are connected in series

along the supply line.

Box #7

Brain Break-FusesWhen you blow a fuse, what does that

mean?Electricity through a circuit causes heat.Fuses melt (or break) when too much

current passes through it; they must be replaced.

This protects expensive electronic equipment.

Box #8-2 notes

Circuit Breakers

Circuit Breakers protect against too much current like fuses, but can be reset.

Box #8-Con’t