Investigating Parallel Circuits: Student Activity Lesson Plan

Transcription

1 : Student Activity Lesson Plan Subject/Strand/Topic: Science / Physics: Electricity Grade(s) / Course(s): 9 / SNC1D Ontario Expectations: PH1.09, PH1.10 Key Concepts: parallel circuits, current, voltage, resistance Link: 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 (~ 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 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 Give students actual circuit components to manipulate as they are working through the learning object. Teacher-Created Resources: Student Activity Lesson Plan Page 1 of 2

2 : Student Activity Lesson Plan Tips and Tricks Circulate to ensure students are progressing through the learning object and activity sheet. Remind students to share control of the computer and switch roles half way through. 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. 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. 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 3 rd load? (9 volts, voltage stays the same.) Teacher-Created Resources: Student Activity Lesson Plan Page 2 of 2

3 Student Activity Pre-Assessment Birthday: 6 1. Circle the correct answer. [2 marks] a. The CURRENT through the source increases / decreases as you add more resistors in parallel. b. The VOLTAGE across each resistor is the same / different 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] 3. For the following circuit, what is the CURRENT at the source? Show your work. [2 marks] I S =? I 1 = 1.0 I 2 = 1.0 I 3 = 1.0 Teacher-Created Resources: Student Activity Pre-Assessment

4 Student Activity Pre-Assessment Birthday : 6 Answer Key 1. Circle the correct answer. [2 marks] a. The current through the source increases as you add more resistors in parallel. 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 = I 1 + I 2 + I 3 Is = Is = 3.0 A I S =? I 1 = 1.0 I 2 = 1.0 I 3 = 1.0 Teacher-Created Resources: Student Activity Pre-Assessment

5 Student Activity Handout Date: 44 INSTRUCTIONS: Use the Circuit Construction Kit to complete the activity sheet. Read How to use the Circuit Construction Kit before you begin. HOW TO USE THE CIRCUIT CONSTRUCTION KIT Action Selecting and moving a piece: Removing a piece: Resizing wire: Attaching pieces: Splitting pieces apart: Options panel: Using the ammeter: Using the voltmeter: Help: How to do the action 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. To remove an item, RIGHT CLICK, and select REMOVE To RESIZE a wire, CLICK and HOLD one of the RED circles at the end of the wire. To ATTACH pieces together, OVERLAP RED circles. To SPLIT pieces apart. RIGHT CLICK on the junction of the pieces (grey circle), and select SPLIT JUNCTION 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. 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. 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). 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 Options panel Ammeter (non-contact) Circuit components Voltmeter Help Teacher-Created Resources: Student Activity Handout Page 1 of 5

6 Student Activity Handout Date: 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 Close switch 1. Switch 1 Switch 2 Switch 3 3. With the non-contact ammeter, measure the current through the source (the battery) and before light bulb 1 (R1). 4. In the Visual box of the Options panel, click LIFELIKE. Observe the brightness of the bulb. 5. Record the results in Table 1. Source Figure 1. R1 R2 R3 6. With the voltmeter, measure the potential difference across the battery A A A A and across light bulb 1 (R1). V 7. Record the results in Table 2. V V V 8. Close switch With the non-contact ammeter, measure the current through the source and before light bulbs 1 and 2 (R1 and R2). Figure 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 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 Close switch 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 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. Teacher-Created Resources: Student Activity Handout Page 2 of 5

7 RECORD YOUR RESULTS Investigating Parallel Circuits Student Activity Handout Date: [21 marks] Table 1. Current as the Number of Light Bulbs (Resistors) in Parallel Increases [12 marks] Number of Resistors Brightness of Light bulbs Through Source Current, I, (Amps) Through each Light Bulb #1 #2 #3 1 Light bulb 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) Across each Light Bulb #1 #2 #3 1 Light bulb 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 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] Teacher-Created Resources: Student Activity Handout Page 3 of 5

8 Student Activity Handout 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). I 1 is the current through the resistor 1, I 2 is the current at resistor 2, etc. A. Is = I 1 + I 2 + I 3 B. Is = I 1 = I 2 = I 3 Explanation:. 6. For the following circuit, what is the current through the source? Show your work. [2 marks] I1 = 1.1 Is =? I2 = 1.1 Teacher-Created Resources: Student Activity Handout Page 4 of 5

9 Student Activity Handout Date: The following questions pertain to your POTENTIAL DIFFERENCE observations. Look at your results from Table 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. V 1 is the potential difference across resistor (light bulb) 1, V 2 is the potential difference at resistor (light bulb) 2, etc. A. Vs = V 1 + V 2 + V 3 B. Vs = V 1 = V 2 = V 3 Explanation: 10. For the following circuit, what is the voltage across resistors 1 and 2? Show your work. [2 marks]. V 1 =? Vs = 12.0 V 2 =? Teacher-Created Resources: Student Activity Handout Page 5 of 5

10 Student Activity Handout Answer Key Name: Answer Key for Teacher 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 #3 1 Light bulb Bright N/a N/a 2 Light bulbs Bright N/a 3 Light bulbs Bright 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 N/a N/a 2 Light bulbs N/a 3 Light bulbs 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, 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 = Consider your answer to Question 2. Circle the correct equation. Explain your answer using your data. [3 marks] A. Is = I 1 + I 2 + I 3 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 = Teacher-Created Resources: Student Activity Handout Answer Key Page 1 of 2

11 Student Activity Handout Answer Key Name: Answer Key for Teacher 6. For the following circuit, what is the current through the source? Show your work. [2 marks] Is = I 1 + I 2 Is = Is = 2.2 A I1 = 1.1 Is =? I2 = 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 = V 1 = V 2 = V 3 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 = V 1 = V = V 1 = V 2 Therefore V 1 and V 2 both = 12.0 V V 1 =? Vs = 12.0 V 2 =? Teacher-Created Resources: Student Activity Handout Answer Key Page 2 of 2

12 Student Activity Post-Assessment 1. Circle the correct answer. [2 marks] Birthday: 6 a. The VOLTAGE across each resistor is the same / different in a parallel circuit. b. The CURRENT through the source increases / decreases as you add more resistors in parallel. 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] I S =? I 1 = 1.2 I 2 = 1.2 I 3 = 1.2 Teacher-Created Resources: Student Activity Post-Assessment

13 Student Activity Post-Assessment 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 increases as you add more resistors in parallel. 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 = I 1 + I 2 + I 3 Is = Is = 3.6 A I S =? I 1 = 1.2 I 2 = 1.2 I 3 = 1.2 Teacher-Created Resources: Student Activity Post-Assessment