Download Investigating Parallel Circuits

Investigating Parallel Circuits: Student Activity Lesson Plan
Subject/Strand/Topic:
Science / Physics: Electricity
Key Concepts:
Grade(s) / Course(s):
9 / SNC1D
Ontario Expectations:
PH1.09, PH1.10
parallel circuits, current, voltage, resistance
Link: http://phet-web.colorado.edu/web-pages/simulations-base.html Click on “Circuit Construction Kit”.
Required Materials: † Pre-Assessment/Answer Key, † Student Activity Handout, † Student Activity Answer Key,
† Post-Assessment/Answer Key, † Data Projector (Optional),
† Circuit Construction Kits [Batteries, Wires, Light Bulbs, Voltmeter, Ammeter] (Optional)
Before Starting:
1. Students should be familiar with simple electric circuits, current, voltage and using ammeters and voltmeters.
2. This activity works best with students in pairs.
3. If doing the optional activity, ensure circuit construction kits are complete and in working order.
Introduction (~ 10 minutes including pre-assessment)
1. Go to computer lab, put students in pairs.
2. Distribute the pre-assessment to each student; collect when complete (5 min).
3. Introduce the learning object to the class:
a. Review current, voltage and what parallel circuits look like.
4. Think-Pair-Share: Q – In a parallel circuit, the more light bulbs we add in parallel, the more paths the current has
to travel. What will happen to the current through the battery as more light bulbs are added to a parallel circuit?
Explain. (current increases as bulbs added in parallel)
Student Activity Handout Explanation (~ 5 minutes)
1. Distribute activity sheet to each student. Students use the learning object to complete the activity.
2. Go over the organization of the activity sheet. Ensure students know where and how to record the data.
Use of Learning Object with Student Activity Handout (~ 25-35 minutes)
1. Give students 2-3 minutes to explore the learning object in their pairs. See if students can make a simple circuit.
2. Stop students. Get students to explain aloud the purpose of the learning object, where the options panel is,
where to find instructions, help, how to build a circuit, etc.
3. If a data projector is available, demonstrate how to build a circuit and use the ammeter and voltmeter. Address
issues that came up when students were explaining what to do (1-2 minutes). If a data projector is not available,
explain verbally.
4. Give students 25-35 minutes to work through the activity in their pairs.
5. If students finish early, have students use the learning object to explore other aspects of parallel circuits, e.g.
conduct the experiment with different resistors, increase the voltage or remove loads.
Optional activity
ƒ Give students actual circuit components to manipulate as they are working through the learning object.
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Investigating Parallel Circuits: Student Activity Lesson Plan
Tips and Tricks
ƒ Circulate to ensure students are progressing through the learning object and activity sheet.
ƒ Remind students to share control of the computer and switch roles half way through.
ƒ The non-contact ammeter was chosen because it is simpler and faster to use than the traditional one. If desired,
the traditional ammeter can be substituted.
ƒ Switching often between small, medium and large view can cause the voltmeter to get ‘lost’ off screen. Close and
reload the program if this happens.
ƒ Ensure students know how to switch between the “schematic” and “lifelike” view.
Consolidation (~ 10 minutes including post-assessment)
1. Once students are finished, distribute the Post-Assessment; collect (5 minutes).
2. Take up activity sheet and / or collect as a ticket-out-the-door.
3. Ask students follow up questions, e.g., Q In a parallel circuit, what happens to the current and brightness of light
bulbs as you add more bulbs in parallel? (Current through each bulb is the same, so brightness stays the
same). Q: Is the current the same or different through source and resistors in a parallel circuit? (different, the
current through the source is the sum of the current through each resistor). Q: The voltage across the source is
9 volts, and there are 3 loads in parallel in the circuit? What is potential difference across the 3rd load? (9 volts,
voltage stays the same.)
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Investigating Parallel Circuits
Student Activity Pre-Assessment
Name: ___________________________
Birthday: ____________________________
6
1. Circle the correct answer. [2 marks]
a. The CURRENT through the source increases
parallel.
b. The VOLTAGE across each resistor is
/
the same
decreases
as you add more resistors in
/
in a parallel circuit.
different
2. In a parallel circuit, what happens to the CURRENT through each resistor as you add more resistors?
Explain. [2 marks]
3. For the following circuit, what is the CURRENT at the source? Show your work. [2 marks]
I1 = 1.0
I2 = 1.0
IS = ?
© 2007 University of Ontario Institute of Technology (UOIT) ~ Permission to Copy
Teacher-Created Resources: Student Activity Pre-Assessment
I3 = 1.0
Investigating Parallel Circuits
Student Activity Pre-Assessment
Name: ___________________________
Birthday : ____________________________
6
Answer Key
1. Circle the correct answer. [2 marks]
a. The current through the source
in parallel.
increases
as you add more resistors
b. The voltage across each resistor is
the same
in a parallel circuit.
2. In a parallel circuit, what happens to the current through each resistor as you add more resistors?
Explain. [2 marks]
The current is through each resistor is the same, it is the current through the source that changes.
3. For the following circuit, what is the current at the source? Show your work. [2 marks]
Is = I1 + I2 + I3
Is = 1.0 + 1.0 + 1.0
Is = 3.0 A
I1 = 1.0
I2 = 1.0
IS = ?
© 2007 University of Ontario Institute of Technology (UOIT) ~ Permission to Copy
Teacher-Created Resources: Student Activity Pre-Assessment
I3 = 1.0
Investigating Parallel Circuits
Student Activity Handout
Name: ___________________________
Date: ____________________________
44
INSTRUCTIONS:
ƒ Use the Circuit Construction Kit to complete the activity sheet.
ƒ Read “How to use the Circuit Construction Kit” before you begin.
HOW TO USE THE CIRCUIT CONSTRUCTION KIT
Action
How to do the action
Selecting and
moving a piece:
To MOVE any piece (wire, battery, etc.) CLICK it, and HOLD. When you release, the piece
will stay where you dropped it. Click and hold to move it again.
Removing a piece:
To remove an item, RIGHT CLICK, and select “REMOVE”
Resizing wire:
To RESIZE a wire, CLICK and HOLD one of the RED circles at the end of the wire.
Attaching pieces:
To ATTACH pieces together, OVERLAP RED circles.
Splitting pieces
apart:
To SPLIT pieces apart. RIGHT CLICK on the junction of the pieces (grey circle), and
select “SPLIT JUNCTION”
Options panel:
Right side of screen. Allows you to select different views (schematic or lifelike), sizes,
types of resistors, tools, etc. You will be told what options to select.
Using the ammeter:
In the OPTIONS panel, check the “NON-CONTACT AMMETER” box. The ammeter will
appear. Move the ammeter over the area you wish to know the current.
Using the voltmeter:
In the OPTIONS panel, check the “VOLTMETER” box. The voltmeter will appear. Move
the leads of the voltmeter over the area of the circuit you wish to know the potential drop
(voltage).
Help:
See bottom of OPTIONS panel. Click “HELP” for generalized instructions on the screen.
Click “MEGA HELP” for a detailed screen shot describing how to use the features.
Construction
area
Ammeter
(non-contact)
Options panel
Circuit
components
Voltmeter
Help
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Investigating Parallel Circuits
Name: ___________________________
Date: ____________________________
Student Activity Handout
MEASURING CURRENT AND VOLTAGE AS RESISTANCE CHANGES IN PARALLEL CIRCUITS
When building your circuit, in the OPTIONS panel on the RIGHT of the screen, in the VISUAL box, click
“SCHEMATIC”.
After your circuit is built, in the OPTIONS panel, click “LIFELIKE” to see what your circuit would actually look
like. Use this to view the brightness of the light bulbs. Do not change the settings of the other components.
PROCEDURE
1. Construct the circuit shown in Figure 1.
The placement of the ammeters and
voltmeters used throughout the whole
experiment is shown in Figure 2.
Switch 1
Switch 2
Switch 3
2. Close switch 1.
3. With the non-contact ammeter, measure
the current through the source (the
battery) and before light bulb 1 (R1).
R1
Source
4. In the “Visual” box of the “Options”
panel, click “LIFELIKE. Observe the
brightness of the bulb.
R2
R3
Figure 1.
5. Record the results in Table 1.
6. With the voltmeter, measure the
potential difference across the battery
and across light bulb 1 (R1).
7. Record the results in Table 2.
A
V
A
V
A
V
A
V
8. Close switch 2.
9. With the non-contact ammeter, measure
the current through the source and
before light bulbs 1 and 2 (R1 and R2).
Figure 2.
10. In the “Visual” box of the “Options” panel, click “LIFELIKE. Observe the brightness of EACH of the light bulbs.
11. Record the results in Table 1.
12. With the voltmeter, measure the potential difference across the battery and across light bulbs 1 and 2 (R1, R2).
13. Record the results in Table 2.
14. Close switch 3.
15. With the non-contact ammeter, measure the current through the source and before light bulbs 1, 2 and 3 (R1, R2,
R3)
16. In the “Visual” box of the “Options” panel, click “LIFELIKE. Observe the brightness of the EACH of the light
bulbs.
17. Record the results in Table 1.
18. With the voltmeter, measure the potential difference across the battery and across light bulbs 1, 2 and 3 (R1, R2
and R3).
19. Record the results in Table 2.
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Investigating Parallel Circuits
Student Activity Handout
Name: ___________________________
Date: ____________________________
RECORD YOUR RESULTS
[21 marks]
Table 1. Current as the Number of Light Bulbs (Resistors) in Parallel Increases [12 marks]
Current, I, (Amps)
Number of
Resistors
Brightness of
Light bulbs
Through Source
Through each Light Bulb
#1
1 Light bulb
#2
#3
N/a
N/a
2 Light bulbs
N/a
3 Light bulbs
Table 2. Potential Difference as the Number of Light Bulbs (Resistors) in Parallel Increases [9 marks]
Potential difference, V, (Volts)
Number of
Resistors
Across Battery
(Source)
1 Light bulb
Across each Light Bulb
#1
#2
#3
N/a
N/a
2 Light bulbs
N/a
3 Light bulbs
WHAT DOES IT ALL MEAN?
The following questions pertain to your CURRENT observations. Look at your results from Table 1.
1. Describe what happened to the current through the source as more light bulbs were added? Justify your
answer by making reference to your data. [2 marks]
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Investigating Parallel Circuits
Student Activity Handout
Name: ___________________________
Date: ____________________________
2. How did the current through the source and through each light bulb (resistor) change as more resistors
were added in parallel. Justify your answer by making reference to your data. [4 marks]
For 1 light bulb:
For 2 light bulbs:
For 3 light bulbs:
Conclusion:
3. What happened to the brightness of the light bulbs as more were added in parallel? [1 mark]
4. Under the same circumstances, if there were 4 light bulbs connected in parallel, what would current
through the source and all 4 light bulbs be? [2 marks]
5. Consider your answer to Question 2. Circle the correct equation. Explain your answer using your data.
[2 marks]
Where,
Is is current through source (battery).
I1 is the current through the resistor 1, I2 is the current at resistor 2, etc.
A.
Is = I1 + I2 + I3
B.
Is = I1 = I2 = I3
Explanation:
.
6. For the following circuit, what is the current through the source? Show your work. [2 marks]
I1 = 1.1
Is = ?
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I2 = 1.1
Investigating Parallel Circuits
Student Activity Handout
Name: ___________________________
Date: ____________________________
The following questions pertain to your POTENTIAL DIFFERENCE observations. Look at your results from Table 2.
7. What happened to the potential difference at the source (battery) as more light bulbs were added? Justify
your answer by making reference to your data. [2 marks]
.
8. How did the potential difference across the source and across each light bulb (resistor) change as more
resistors were added in parallel. Justify your answer by making reference to your data. [4 marks]
For 1 light bulb:
For 2 light bulbs:
For 3 light bulbs:
Conclusion:
9. Consider your answers to Questions 7 and 8. Circle the correct equation. Explain your answer using
your data. [2 marks]
Where,
Vs is the potential differnce at the source.
V1 is the potential difference across resistor (light bulb) 1, V2 is the potential difference at resistor
(light bulb) 2, etc.
A.
Vs = V1 + V2 + V3
B.
Vs = V1 = V2 = V3
Explanation:
10. For the following circuit, what is the voltage across resistors 1 and 2? Show your work. [2 marks]
.
V1 = ?
Vs = 12.0
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V2 = ?
Investigating Parallel Circuits
Name: Answer Key for Teacher
Student Activity Handout Answer Key
Table 1. Current as the Number of Light Bulbs (Resistors) in Parallel Increases [12 marks]
Current, I, (Amps)
Number of
Brightness of
Through Source
Through each Light Bulb
Resistors
Light bulbs
#1
#2
1 Light bulb
Bright
0.88
0.88
N/a
2 Light bulbs
Bright
1.75
0.88
0.87
3 Light bulbs
Bright
2.58
0.87
0.86
#3
N/a
N/a
0.85
Table 2. Potential Difference as the Number of Light Bulbs (Resistors) in Parallel Increases [9 marks]
Potential difference, V, (Volts)
Number of
Across Battery
Across each Light Bulb
Resistors
(Source)
#1
#2
#3
1 Light bulb
9.0
8.9
N/a
N/a
2 Light bulbs
9.0
8.8
8.7
N/a
3 Light bulbs
9.0
8.7
8.6
8.5
1. Describe what happened to the current through the source as more light bulbs were added? Justify your
answer by making reference to your data. [2 marks]
The current through the source increased each time another light bulb was added in parallel. For
example, for 1 bulb the current was 0.88 A, for 2 bulbs, 1.75 A, and for 3 it was 2.58 A.
2. How did the current through the source and through each light bulb (resistor) change as more resistors
were added in parallel. Justify your answer by making reference to your data. [4 marks]
For 1 light bulb: current through bulb and the source was the same, 0.87.
For 2 light bulbs: current through each bulb was the same, 0.87, and through the source was 1.75 A
For 3 light bulbs: current through each bulb was the same, 0.87, and through the source was 2.58 A
Conclusion: The current through each resistor stays the same as more resistors are added.
3. What happened to the brightness of the light bulbs as more were added in parallel? [1 mark]
Brightness of the light bulbs did not change.
4. Under the same circumstances, if there were 4 light bulbs connected in parallel, what would current
through the source and all 4 light bulbs be? [2 marks]
Current through source = 3.48 A
Current through each light bulb = 0.87
5. Consider your answer to Question 2. Circle the correct equation. Explain your answer using your data.
[3 marks]
A.
Is = I1 + I2 + I3
Explanation:
A. The current through the source is the sum of the current through each resistor connected in
parallel in the circuit. For 3 light bulbs, the current through the source was 2.58 A which equals the
sum of the current at each of the 3 light bulbs. 2.58 = 0.87 + 0.86 + 0.85
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Investigating Parallel Circuits
Name: Answer Key for Teacher
Student Activity Handout Answer Key
6. For the following circuit, what is the current through the source? Show your work. [2 marks]
Is = I1 + I2
I1 = 1.1
Is = 1.1 + 1.1
Is = 2.2 A
Is = ?
I2 = 1.1
7. What happened to the potential difference at the source (battery) as more light bulbs were added? Justify
your answer by making reference to your data. [2 marks]
Potential difference at the source did not change. Regardless of how many light bulbs the potential
difference was the same at 9.0 V.
8. How did the potential difference across the source and across each light bulb (resistor) change as more
resistors were added in parallel. Justify your answer by making reference to your data. [4 marks]
For 1 light bulb: PD across bulb and the source was the same ~ 8.9 V.
For 2 light bulbs: PD across each bulb and source was the same, ~ 9.0
For 3 light bulbs: PD across each bulb and source was the same, ~ 9.0
Conclusion: The potential difference across each resistor and the source did not change as more
resistors were added in parallel.
9. Consider your answers to Questions 7 - 9. Circle the correct equation. Explain your answer using your
data. [2 marks]
B.
Vs = V1 = V2 = V3
Explanation:
B. The PD at the source is the same as at all points in the circuit. The PD was ~ 9.0 V at the source
and across all resistors regardless of how many.
10. For the following circuit, what is the voltage at resistor 2? Show your work. [2 marks]
.
Vs = V1 = V2
V1 = ?
12.0 = V1 = V2
Therefore V1 and V2 both = 12.0 V
Vs = 12.0
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V2 = ?
Investigating Parallel Circuits
Student Activity Post-Assessment
Name: _____________________________
Birthday: ______________________________
6
1. Circle the correct answer. [2 marks]
a. The VOLTAGE across each resistor is
the same
b. The CURRENT through the source increases
parallel.
/
/
different
decreases
in a parallel circuit.
as you add more resistors in
2. In a parallel circuit, what happens to the CURRENT through each resistor as you add more resistors?
Explain. [2 marks]
3. For the following circuit, what is the CURRENT at the source? Show your work. [2 marks]
I1 = 1.2
I2 = 1.2
IS = ?
© 2007 University of Ontario Institute of Technology (UOIT) ~ Permission to Copy
Teacher-Created Resources: Student Activity Post-Assessment
I3 = 1.2
Investigating Parallel Circuits
Student Activity Post-Assessment
Name: _____________________________
Birthday: ______________________________
6
Answer Key
1. Circle the correct answer. [2 marks]
a. The voltage across each resistor is
the same
in a parallel circuit.
b. The current through the source
in parallel.
increases
as you add more resistors
2. In a parallel circuit, what happens to the current through each resistor as you add more resistors?
Explain. [2 marks]
The current is through each resistor is the same, it is the current through the source that changes.
3. For the following circuit, what is the current at the source? Show your work. [2 marks]
Is = I1 + I2 + I3
Is = 1.2 + 1.2 + 1.2
Is = 3.6 A
I1 = 1.2
I2 = 1.2
IS = ?
© 2007 University of Ontario Institute of Technology (UOIT) ~ Permission to Copy
Teacher-Created Resources: Student Activity Post-Assessment
I3 = 1.2