Buggé: DC Circuits 2
Searching for Patterns in Series and Parallel Circuits
Use the Circuit Construction Kit on phet.colorado.edu (DC Circuits only) to build the following circuits.
After building each circuit, use the ammeter and voltmeter to measure the current in the wires and the potential
difference across each light bulb in the simulated circuit. What patterns do you come up with as you build the
circuits?
Note: When finding the total potential difference for the entire circuit (∆Vtotal) we are not looking for the sum of
all the voltmeter readings. Instead, find the potential difference across the entire circuit. When finding the total
current ( Itotal) we are again not looking for the sum of all the ammeter readings, but the total current for the
entire circuit.
2.1 Series Circuit - Connect 3 bulbs in series. DIAGRAM using half of a page!
a. Add an ammeter to measure the TOTAL current. Draw it in the diagram and record the total
current next to the ammeter in the diagram.
b. Take the ammeter out of the circuit and put it in the circuit again to measure the current at
another location. Draw it in the diagram and record the new current next to the ammeter in the
diagram.
c. Use the voltmeter to measure the TOTAL potential difference across the circuit and the potential
difference across each bulb. Draw the 4 positions of the voltmeter on your diagram, and record the
values of the voltage next to the voltmeters in the diagram.
d. Compare the current through each bulb to the total current. Record the pattern you observe.
e. Compare the potential difference across each bulb to the total potential difference. Record the
pattern you observe.
Diagram and Patterns for SERIES Circuit
Some lesson activities adapted from ALG and PUM, Etkina and Van Heuvelen, 2010
Buggé: DC Circuits 2
2.2 Parallel Circuit - Connect 3 bulbs in parallel. DIAGRAM using half of a page!
a. Add an ammeter to measure the TOTAL current. Draw it in the diagram and record the total
current next to the ammeter in the diagram.
b. Take the ammeter out of the circuit and put it in the circuit again to measure the current at
through EACH resistor. Draw it in the diagram and record each current next to the ammeter in
the diagram.
c. Use the voltmeter to measure the TOTAL potential difference across the circuit and the potential
difference across each bulb. Draw the 4 positions of the voltmeter on your diagram, and record the
values of the voltage next to the voltmeters in the diagram.
d. Compare the current through each bulb to the total current. Record the pattern you observe.
e. Compare the potential difference across each bulb to the total potential difference. Record the
pattern you observe.
Diagram and Patterns for PARALLEL Circuit
Some lesson activities adapted from ALG and PUM, Etkina and Van Heuvelen, 2010
Buggé: DC Circuits 2
2.3 Combo Circuit - Build a combination circuit. DIAGRAM using half of a page!
a. Add an ammeter to measure the TOTAL current. Draw it in the diagram and record the total
current next to the ammeter in the diagram.
b. Take the ammeter out of the circuit and put it in the circuit again to measure the current at
through EACH resistor. Draw it in the diagram and record each current next to the ammeter
in the diagram.
c. Use the voltmeter to measure the TOTAL potential difference across the circuit and the
potential difference across each bulb. Draw the 4 positions of the voltmeter on your diagram,
and record the values of the voltage next to the voltmeters in the diagram.
d. Compare the current through each bulb to the total current. Record the pattern you observe.
e. Compare the potential difference across each bulb to the total potential difference. Record the
pattern you observe.
Diagram and Patterns for COMBO Circuit
Some lesson activities adapted from ALG and PUM, Etkina and Van Heuvelen, 2010
Buggé: DC Circuits 2
Summarize your findings:
Series
Parallel
Current through light bulbs:
Current through light bulbs:
Potential difference across light bulbs:
Potential Difference across light bulbs:
Circuit Junctions
Develop a rule for the current going into and coming
out of a junction.
Circuits Loops
Develop a rule for the potential difference of all
elements in a loop.
Did you know?
Elements in Series: When circuit elements are connected in series, the current through each element is the
same and the potential difference across the elements is the sum of the potential differences across each
element:
I1 = I2 = I3 = Itotal
ΔV1 + ΔV2 + ΔV3 = ΔVtotal
Elements in Parallel: When circuit elements are connected in parallel, the potential difference is the same
across each element and the total electric current is the sum of the currents through each element:
ΔV1 = ΔV2 = ΔV3 = ∆Vtotal
Itotal = I1 + I2 + I3
2.4 Observe and Explain The readings of three ammeters are
shown at the right. What can you say about the magnitude of the
current through each of the light bulbs? Explain the pattern.
A
10 mA
A
10 mA
A
10 mA
2.5 Predict
(a) For the diagram to the right use analogies and the ideas of
potential difference and current to rank the brightness of the bulbs.
List the brightest bulb first. Indicate whether any bulbs are equally
bright. Explain your ratings.
(b) Check your prediction using the PhET Circuit Construction Kit
and write your conclusions.
Some lesson activities adapted from ALG and PUM, Etkina and Van Heuvelen, 2010
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Buggé: DC Circuits 2
2.6 Complete the following activity.
a. Rank the bulbs in the circuit shown to the above according to their
brightness when the switch is open.
b. Now rank the bulbs in the circuit when the switch is closed.
c. Predict how the brightness of each of the first three bulbs changes
after the switch is closed.
d. Test your prediction using the PHET Circuit Construction Kit and
write your conclusions.
2.7 Answer the following in a brief paragraph: Jim says that a battery is a source of constant current. Do you
agree or disagree with Jim. If you agree what arguments do you have to support his opinion? If you
disagree, how can you convince Jim in you opinion. In general, what does it take to convince somebody in
physics?
2.8 Using the Circuit Construction Kit, determine how connecting two or more batteries in series affects the
total potential difference of the circuit. How does this differ from connecting two or more batteries in
parallel?
Some lesson activities adapted from ALG and PUM, Etkina and Van Heuvelen, 2010