Download 4.2.2 – Parallel Circuits NAME: DATE: PARTNERS:


4.2.2
–
Parallel
Circuits
NAME:
1
DATE:
PARTNERS:
Purpose:
To
study
the
properties
of
a
basic
parallel
circuit.
Materials:
1.
2.
3.
4.
5.
2
bulbs,
and
bulb
holders
1
AA
battery
8
alligator
clips
1
Ammeter
(0‐1
A)
1
Voltmeter
(0‐3
V)
Diagram:
Light
bulbs
in
battery
holders
Procedure:
1. Connect
a
simple
series
circuit
with
ONE
bulb,
and
one
battery.
Measure
the
current
with
the
ammeter
(in
series)
of
this
basic
series
circuit:
4.2.2
–
Parallel
Circuits
2
2. PREDICT:
If
you
add
a
2nd
bulb
in
parallel,
as
shown
in
the
diagram
above,
will
both
bulbs
be
equally
bright,
or
will
there
be
a
difference
in
brightness?
Explain.
What
will
happen
to
the
brightness
of
the
first
bulb?
Also,
will
the
current
in
the
two
branches
differ,
or
be
the
same?
3. DISCUSS:
Talk
with
your
group
about
your
prediction.
Are
there
any
different
predictions
in
your
group?
If
so,
write
them
down,
with
the
explanation
behind
each
one.
When
your
group
reaches
a
consensus,
move
on
to
the
next
step.
4. OBSERVE:
Connect
the
second
bulb
to
the
circuit
as
shown
in
the
diagram.
Record
your
observations
about
the
brightness
of
the
bulbs.
Were
your
predictions
correct?
4.2.2
–
Parallel
Circuits
5. (c)
(a)
1
2
(b)
This
parallel
circuit
can
be
thought
of
as
two
current
loops
(1
and
2),
as
indicated
in
the
above
diagram.
Measure
the
current
in
the
following
places.
Note:
to
measure
current
properly,
the
ammeter
must
be
connected
in
series.
Current
in
loop
2,
between
the
two
bulbs
–
noted
by
ammeter
position
(a):
Current
in
loop
1
–
noted
by
ammeter
position
(b):
Total
current
in
the
circuit
‐
noted
by
ammeter
position
(c):
6. a)
Compare
the
currents
in
loops
1
and
2
with
each
other.
What
is
the
relationship
here?
b)
Compare
the
currents
in
each
loop
with
the
total
current
in
the
circuit.
What
is
the
relationship
here?
3
4.2.2
–
Parallel
Circuits
c)
Compare
the
total
current
in
parallel
with
two
bulbs,
with
the
total
current
for
two
bulbs
in
series,
with
one
battery.
(May
need
to
refer
back
to
Series
Circuit
activity.)
Explain
your
findings.
Questions:
1. Remove
one
of
the
bulbs.
What
happens
to
the
brightness
of
the
other
one?
Why?
2. Measure
the
voltage
across
each
bulb
in
the
parallel
circuit
using
the
voltmeter
(both
bulbs
screwed
in)
Bulb
1:
(V)
Bulb
2:
(V)
Compare
the
voltages
across
each
bulb,
and
compare
these
voltages
with
the
voltage
of
the
battery:
4
4.2.2
–
Parallel
Circuits
Now,
measure
the
voltage
across
one
of
the
bulbs
when
the
other
one
is
unscrewed
from
its
holder:
Is
the
voltage
across
a
bulb
changed
when
an
identical
bulb
is
placed
in
parallel
with
it?
Explain
how
this
is
different
from
a
series
circuit.
3. Are
the
outlets
in
your
home
arranged
in
parallel
or
series?
Why
are
they
designed
this
way?
4. If
you
were
to
design
your
own
chandelier
for
your
dining
room,
would
you
want
the
bulbs
to
be
in
series,
or
parallel?
Explain
why.
5
4.2.2
–
Parallel
Circuits
6
5. As
a
review,
sketch
how
you
would
wire
a
3‐bulb
circuit
as
a
series
circuit,
and
a
parallel
circuit.
Resources:
Cunningham,
James
and
Norman
Herr.
Hands‐On
Physics
Activities
With
Real‐Life
Applications,
(West
Nyack:
The
Center
for
Applied
Research
in
Education,
1994),
p.
581
4.2.2
–
Parallel
Circuits
7
Summary
and
Suggestions
for
the
Future:
(Please
attach
extra
pages
as
necessary
to
fully
answer
these
questions)
1.
What
were
the
important
concepts
of
physics/science
that
you
learned
from
this
activity?
What
else
did
you
learn?
2.
Can
you
think
of
alternative
hands‐on
ways
in
which
these
concepts
could
be
demonstrated?
Can
you
suggest
any
improvements
to
these
activities?
3.
What
changes
would
you
make
to
teach
these
activities
in
a
Grade
7‐8
classroom?
What
difficulties
can
you
foresee?