Download Searching for Patterns in Series and Parallel Circuits

Kreutter/Costello: DC Circuits 3
Searching for Patterns in Series and Parallel Circuits
Construct the following series and parallel circuits in the Circuit Construction
Kit.
After building each circuit, use the ammeter and voltmeter to measure the current
in the wires and the potential difference (voltage) 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 (voltage) for the entire
circuit (∆Vtotal) we are not looking for the sum of all the voltmeter readings.
Instead, find the potential difference (voltage) across the entire circuit, as
shown in the diagrams below. 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.
3.1
Current through each
Ammeter
I1 =
I2 =
Potential Difference
(voltage) across each
element
Patterns in current
Patterns in potential
difference (voltage)
∆Vbattery =
A1
∆V1 =
1
V1
1
V1
A2
3.2
Current
through each
Ammeter
I1 =
A1
I2 =
Itotal =
Potential
Difference
(voltage)
Across each
Element
DV battery =
DV 1 =
DV 2 =
DV total
Patterns in
current
Patterns in
potential
difference
(voltage)
V total across bulbs
A2
2
across bulbs
=
V2
Kreutter/Costello: DC Circuits 3
3.3
Current
through
Each
Ammeter
I1 =
I2 =
A1
I3 =
A2
Itotal =
A3
1
V1
Vtotal
2
V2
2
V2
Potential ∆Vbattery =
Difference
(voltage) ∆V1 =
Across
each
∆V2 = _
Element
∆Vtotal =
Patterns
in current
Patterns
in
potential
difference
(voltage)
3.4
A1
Current
through each
Ammeter
Potential
Difference
(voltage)
Across each
Element
I1 =
I2 =
I3 =
I4 =
Itotal =
∆Vbattery =
∆V1 =
∆V2 =
∆V3 =
∆Vtotal = _________
Patterns in
current
Patterns in
potential
difference
(voltage)
A3
A2
1
V1
Vtotal
A4
3
V3
Kreutter/Costello: DC Circuits 3
3.5
Current through
Each Ammeter
Potential
Difference
(voltage) Across
each Element
Patterns in
current
Patterns in
potential
difference
(voltage)
I1 =
A1
∆Vbatteries =
∆V1 =
1
V1
3.6
Current
through Each
Ammeter
Potential
Difference
(voltage)
Across each
Element
Patterns in
current
Patterns in
potential
difference
(voltage)
I1 =
A1
∆Vbatteries =
1
V1
∆V1 =
3.7 Summarize your findings:
Series
Parallel
Batteries:
Batteries:
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 (voltage) of all elements in
a loop.
Kreutter/Costello: DC Circuits 3
3.8 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
3.9 Predict
(a) For the diagram to the right use the
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.
1
2
3
4
Kreutter/Costello: DC Circuits 3
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 (voltage) across
the elements is the sum of the potential differences (voltages) across each
element:
I1 = I2 = I3 = Itotal
V1 + V2 + V3 = Vtotal
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:
V1 = V2 = V3 = ∆Vtotal
Itotal = I1 + I2 + I3