parallel circuits 8 note boxes. quick review the electrons that move to make electricity come mostly...
TRANSCRIPT
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