Transcript Series and Parallel Circuits

Circuits
Circuits are closed paths that
form a loop
Circuits
There are three basic parts to
a circuit:
1. Energy source (battery,
etc)
2. Wires
3. Load (light bulb, radio,
etc)
Circuits
What does the load do?
~The load changes electrical
energy into OTHER forms of
energy
Ex: thermal, light,
mechanical, etc.
Switches
~A switch is used to open
and close a circuit
~When a switch is closed, it
is “on”
~When a switch is open, it is
“off”
Series and
Parallel Circuits
Circuits…
Can
either be series
or parallel.
Series
Current
only takes
one path for electrons
If there is any break
in the circuit, the
current will stop
flowing
Lights in a Series
Series
If
you add a resistor (like
another light):
Total
resistance goes UP
since all the current has
must go through each
resistor.
If one lightbulb goes
out…
If you remove a light
bulb or one burns
out—all go out!
If one lightbulb goes
out…
If
your home was wired
this way, it would be very
difficult! Imagine if your
fridge and a lamp were
wired in series. When one
was off, the other wouldn’t
work.
Why Do they
exist?
They
are helpful!
Example: burglar alarms:
if the circuit fails, there is
no current. When the
current goes out, the
alarm sounds.
Voltage in Series
Voltage
is
reduced by each
resistance –
voltage drop
Voltage in Series
This
means, as you
add light bulbs, they
get dimmer. They
are sharing the same
current.
Parallel Circuits
Has
at least one point
where current divides
More than one path for
current to flow
Paths are also known as
branches
Lights in Parallel
Parallel:
Your
home is wired in
parallel. This school is
wired in parallel.
Parallel:
Charges
in a parallel
circuit have more than
one path on which they
can travel.
Parallel:
Charges
in a parallel
circuit have more than
one path on which they
can travel.
Parallel:
If
you add a resistor:
Total resistance goes
down
Total current goes up
when you add
another path
Removing a Light
Bulb
If
you remove a light
bulb or one burns out,
the others stay on
because the circuit is
still closed.
Removing a Light
Bulb
You can connect loads
that need different
currents to the same
parallel circuit.
Each branch of the
circuit can work by itself.
Current in Parallel
Current
flows into a
branching point, the
same total current must
flow out again
Current depends on
resistance in each
branch
Voltage in Parallel
Voltage
is the
same across each
branch – because
each branch is on
the same wire
Toll Road—Circuit
Analogy
Toll Booth
Explanation
 Adding
toll booths in series
increases resistance and
slows the current flow.
 Adding toll booths in
parallel lowers resistance
and increases the current
flow.
Batteries in Series
and Parallel:
In
series—The voltage
is increased.
In parallel—No
change in voltage;
these batteries will
last longer!
One More FINAL
Thing:
Two
Types of Current:
DC—Direct Current—
produced by solar cells
and chemical cells
(batteries)
Current only flows in
one direction.
nd
2 type of current:
AC—Alternating
Current
Current flows back and
forth (alternates)
Found in homes
Generators produce AC
current