Transcript Series and Parallel Circuits

Series and
Parallel Circuits
Circuits
Can
either be series
or parallel.
Series
Current
only takes
one path for
electrons
Current flows
through every part of
the circuit
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.
Adding Resistors to
Series:
Current in the circuit
will go DOWN (lights
will dim)
If you remove a light
bulb or one burns
out—all go out!
Current in Series
Current
is the same at
all points
Use Ohm’s Law to find
current using
resistance and voltage
Voltage in Series
Voltage
is
reduced by each
resistance –
voltage drop
Resistance in Series
Add
up all resistors to
get total
Total
resistance will go
up because all of the
current must go through
each resistor.
Sample Problem #1

1.
2.
3.
Draw a series circuit with two 1.5
V batteries, 3 resistors, and a
current of 0.5 A.
What is the total voltage of the
circuit?
What is the resistance of each
resistor?
What is the voltage drop across
each resistor? Label on your
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:
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.
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
Resistance in
Parallel
Calculate
current in
each branch based on
resistance in each
branch by using
Ohm’s Law
Practice problem #2

1.
2.
Draw a parallel circuit with
two resistors (one on each
branch) and a 12 V battery.
What is the voltage through
each resistor?
What is the current flowing
through each branch?
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