Section 6: Current, Voltage, and
Resistance in Parallel and Series Circuits
Lesson 1




Journal/Notebook
o Remind the students to begin a new page in their Active Physics Log. The
heading of the page should be Section 6: Current, Voltage, and Resistance
in Parallel and Series Circuits. Also record the section and page number
in your Table of Contents.
What do you see?
o Ask your class to look at the cartoon and write a brief description of the
scene in their log. They may have never encountered a switching set-up as
shown in the cartoon but hopefully they can create a scenario in which the
lamp can be controlled by two switches.
o (3 minutes)
What do you think?
o The two questions – 1) List at least three different kinds of automatic
switching devices. 2) What are the conditions that cause the on/off action
of the switch? Should be answered in their Active Physics Log.
o (4 minutes)
Investigate – Switches in Parallel Circuits
o Using a hand-cranked generator or a battery or a DC voltage supply, 3
light bulbs and lots of wires tell your students to build the circuit that is
shown on the top of page 645. Emphasize that they need wires with clips
on each end so that the bulbs can be connected securely in parallel. It
would be a good idea to model this by building one in front of the class
and labeling each wire with a number (use masking tape). Each student
must then draw the schematic diagram in their log numbering each wire.
Ask the class whether the circuit is parallel (1 finger) or series (2 fingers).
o Ask the class to write on their white boards which wire should be replaced
with a switch to turn all three bulbs on and off. Any of the following
wires may be replaced with a switch = 1, 2, 9, & 10. When checking the
class responses point out that the switch must be in series with whatever
needs to be turned on or off.
o Have each lab team replace the predicted wire with a switch and see if it
does turn off all three bulbs.
o Now ask the class to write on their white boards which wire should be
replaced with a switch to turn off only bulb A. The correct answer is wire
11 or 12. Then have each team replace the predicted wire with a switch
and see if it does work. Repeat for bulb B (answer is wires 13 or 14) and
then bulb C (answer is wires 4, 5, 6 or 7).
o Tell the students to draw diagrams for each of the examples including the
switches in their logs.
o


(12 minutes)
Investigate – Voltmeters and Ammeters in Parallel Circuits
o Your students need to place a voltmeter in the parallel circuit to measure
the voltage drop across any light bulb. As stated in the textbook, the
positive side of the voltmeter should be connected to the positive side of
the generator or else the voltmeter will try to produce a negative reading.
If it does, reverse the wires on the voltmeter. The power supply can either
be a battery or a hand-cranked generator. The battery or DC voltage
source is preferable because the voltage will be constant and give better
results where as with a hand-cranked generator the voltage will vary. If
your class does use hand-cranked generators, try and have the students
crank at a constant rate which will give a nearly constant voltage.
o Students should place an ammeter in the circuit to measure the current
though the first light bulb which is similar to placing a switch in the
circuit. Switches are always placed in series with the bulb (load) and so
should an ammeter.
o Students must record the voltage across the first light bulb as well as the
current through it.
o Repeat the investigation for the second and then the third bulb and record
all results in your log in a table like the one on page 646.
o (12 minutes)
HW
o Physics to Go
o Page 658 # 1, 2 = important for the Chapter Challenge
o Page 658 3, 4, 5