Parallel and Series Circuits

Transcription

1 Parallel and Series Circuits Gabriel Alsina Rationale: This lesson will introduce students to series and parallel circuits and should follow lessons introducing circuit building in general. This lesson helps students understand more about how electricity works while keeping it all grounded and connected to real circuitry. It all also satisfies the following Wyoming State Science Standards: SC SC SC SC Energy and Matter: Demonstrate an understanding of types of energy, energy transfer and transformations, and the relationship between mass and energy. Students investigate the relationships between science and technology and the role of technological design in meeting human needs. Students properly use appropriate scientific and safety equipment, recognize hazards and safety symbols, and observe standard safety procedures. Students examine how scientific information is used to make decisions. Interdisciplinary connections of the sciences and connections to other subject areas and career opportunities. The role of science in solving personal, local, national, and global problems. Objectives: This lesson will give students an opportunity to use their scientific inquiry abilities while learning more about electricity and circuits. Each student will have an opportunity to construct several circuits and measure the voltage and currents present in these circuits. Students will learn how to build simple circuits by looking at circuit diagrams and get more practice in measuring voltage and current using a multimeter. Emphasis will be placed on series and parallel circuitry and their properties. Students will also learn how to troubleshoot circuits. Materials: Multimeters Breadboards with voltage source Required LEDs Pre-cut and stripped wires Lab worksheets Troubleshooting tips page Statement of Engagement: Students will begin this lesson by playing around with circuit simulation software available at Their task will be to light up 3 light bulbs with only 2 batteries. This should give them a fun way to start interacting with the circuits. Many of them will probably gravitate towards a series circuit although a few parallel circuits might also be produced. The teacher should then use these student produced circuits as a launching point for the day s lesson.

2 Minute by Minute Breakdown: Time (min) What the teacher is doing Start students on circuit simulation with the task described above. Facilitate when necessary Use student constructed circuits to illustrate differences between series and parallel circuits. 5 Give a brief introduction to circuit troubleshooting using the circuit simulation software. Ask students how they would proceed when a light wouldn t come on in their circuits. 5 Introduce today s lab. Hand out materials and worksheets. Group students Answer questions and ensure students are on task and working through the labs Once finished, have the students answer any remaining questions on their worksheets and clean up their work areas Discuss results with the entire class. Ask class what the main differences between series and parallel are. Have students share any troubleshooting stories. What the student is doing Experiment with components and try to accomplish task. Presenting their circuits. Listening and asking questions. Listening and proposing possible solutions to encountered problems. Listening and following instructions. Working on labs. Finish worksheets and clean up. Participate in discussion, ask questions. Troubleshooting Tips If a problem arises with the lab here are some things to try: 1. Start simple a. Is it wired correctly? b. Are all the connections good or is one loose? c. Is the potentiometer turned all the way to one side or another (if connected)? If so this may be adding too much resistance to the circuit so try turning it the other way. d. Is there enough light? Solar panels are very picky about the amount of light they need. The more the better. Lab 2: Task 1 actually experiments with shading part of the panel. 2. Swap identical components and check to see if it fixes the problem. If it does, discard the replaced component. 3. Remove any parallel components to see if the circuit will begin working. 4. Divide the circuit into smaller systems and test each individually.

3 Lab #1: Circuit Introduction NOTE: To measure voltage you must measure it across the LED or voltage source. To measure current you must connect the ammeter in series with the circuit. Task 1: Parallel Circuits 1) Connect the circuit shown in figure 1. This connects the LED s in parallel. See how they are on opposite sides of the box the wires make. Figure 1 2) Take measurements after the circuit above is constructed. I stands for current and V for voltage. I source I green LED I yellow LED I green + I yellow 3) Does I green + I yellow equal the current out of the voltage source? Why? 4) Disconnect one LED, does the other LED turn off? Why? 5) Reverse the wires going from the voltage source to the LEDs. What happens? Why?

4 Task 2: Series Circuits 1) Connect the circuit as shown in figure 2. Notice how the wires make a continuous loop, this is known as a series connection. Figure 2 2) Take the following voltage measurements after the circuit above is constructed. V green V yellow V green + V yellow 3) Does V green + V yellow =? Why? 4) Take the following current measurements after the circuit above is constructed. I voltage source I between LEDs 5) Are the two currents equal? Why? 6) Disconnect one LED, does the other LED turn off? Why?

5 Task 3: Series with a Variable Resistor 1) Connect the circuit as shown in figure 3. This is also a series connection; we just added a variable resistor, called a potentiometer (Pot). Figure 3 Pot 10k 40% 2) Try turning the potentiometer. What happens? Why do you think this happens? 3) Is the resistance in the potentiometer higher or lower when the lights are dimmed versus full brightness? 4) As the extra resistance is added does the current in the circuit increase or decrease? 5) With the LED s dimmed, take the following measurements. V potentiometer V green V yellow 6) Add V potentiometer + V green + V yellow. Is it equal to? Why or why not?