University of Virginia Physics Department Series and Parallel Circuits A Physical Science Activity

2003 Virginia SOLs

• PS.1
• PS.11

Objectives

Students will

• identify observable differences in lights wired in series and in parallel;
• infer the wiring of a string of holiday lights and give a description of how they work.

Motivation for Learning

Demonstration

Materials

• One string of older holiday lights (when one light goes out, they all do). These can be purchased at any dollar store as the holiday season approaches
• One string of newer holiday lights (when one light goes out, the rest stay lit)

Procedure

1. Set-up a demonstration using the two separate strings of holiday lights.
2. Turn the lights on. Then, ask the kids "What will happen if I remove this light?" and do it.
3. Let the students record what happened and write an explanation on why they think it happened that way.
4. Repeat this process using the other strand of lights. (Do not give them the answers as this is on the data sheet and can be used for discussion when the actual hands-on lab is completed).

Student Activity

To print out the Student Copy only, click here.

Materials

• One 6-volt lantern battery or 4 "D" size batteries
• Two light bulb holders
• Two light bulbs (6.3 volts)
• One switch
• Four pieces of bell wire about 8 inches long each piece (ends stripped)
• Wire cutters/strippers

Procedure

Discuss parallel and series circuits from the demonstration with students. Tell them that there are two different configurations for bulbs in a circuit. One is called series (like the first string of lights you saw) and the other is called parallel (like the second set of lights you saw).

1. After the teacher discusses series and parallel circuits with the class, answer questions 1 and 2 on your data sheet.
2. Using the batteries, 2 bulbs, wires, and switch that you have, construct two circuits -- one that is in series, and the other that is in parallel.
3. Answer questions 3 and 4 on your data sheet.
4. Answer the rest of the questions on your data sheet.

Data Sheet

To print out the Data Sheet only, click here.

What did you observe about the first string of holiday lights (the one in series)? What did you observe about the second string of holiday lights (the one in parallel)? Draw a diagram that represents your series circuit. Use your diagram to explain why it is named a series circuit. Draw a diagram that represents your parallel circuit. Use your diagram to explain why it is named a parallel circuit. In a series circuit, what happens when the first bulb is unfastened? What happens when the second bulb is unfastened (and the first one is re-fastened)? In a parallel circuit, what happens when the first bulb is unfastened? What happens when the second bulb is unfastened (again with the first one reconnected)? Is there any difference in the behavior of the lights when you unfasten the first bulb as opposed to the second bulb? In which circuit did the two light bulbs appear brighter? Why is it important that connections in a circuit be tight? Why do you have to close the switch? Explain your answer. How do you know that you had a complete circuit? How do you think the lights in your house are configured? Explain your answer. What would happen if the lights in your house were configured opposite to your answer in number 14.

Answers to Data Sheet

1. The entire string of lights went out when one bulb was taken out.
2. The rest of the lights remained lit when one bulb was taken out.
3. Diagrams may vary, but they should look similar to the following:
   
   
4. Diagrams may vary, but they should look similar to the following:
   
   
5. All bulbs go out.
6. All bulbs go out.
7. The first light goes out and the second light bulb remains lit.
8. The second light bulb goes out and the first one remains lit.
9. There is no difference. Each time, either the other light goes out or it remains lit.
10. Parallel.
11. If there is any break in the contact, the electrons will not be able to flow between the parts of the circuit. If this happens, the circuit will not be complete.
12. Closing the switch will complete the circuit and allow the electrons to flow.
13. The lights were lit.
14. They are configured in parallel. Each light comes on and goes off by itself. One light does not affect the others in the house.
15. You could never just have one light on. All of them would either be on or be off.

Extensions

There are several extensions that a teacher can use when working with series and parallel circuits. One activity would be to teach your students how to use an ammeter and a voltmeter. The ammeter can be connected between the switch and the battery in a simple circuit. The students then can flip the switch to make a complete circuit and read the ammeter. The ammeter measures the current through the circuit. You can have the students place the ammeter in different places to see if the current changes.

When using the voltmeter, the voltmeter is connected across the conductor being measured. You can add batteries to this also and read the voltage and compare to only using one battery. Be careful when adding batteries to avoid burning out the light bulb.

Once the students are comfortable reading the ammeter and voltmeter, the students can put their series and parallel circuits back together, add the ammeter and voltmeter, and take readings that can be put into a data table. The ammeter and voltage meter can be added separately and together.

Students with Special Needs

Some children will need help to actually hook the wires to the battery, switch, and the light. I recommend alligator clips for those children who have physical disabilities with their hands. Have your resource teacher help you but give them advance warning that you will need their assistance this day.

Click here for further information on laboratories with students with special needs.

Assessment

Data sheet to be completed during the laboratory.