Conductors and Insulators
November 16, 2000
Brief Description of the Lesson: This will be a hands-on experiment in which the students will learn about conductors and insulators by testing various materials to determine whether or not they conduct electricity.
Grade Level and Course of Study Content Standard: Grade 4
· Students will explore the forces that move objects (i.e. electricity) (p. 30, #19).
· Students will explain the differences between conductors and nonconductors (p. 50, #31).
Background Information for the Teacher:
In 1752, Benjamin Franklinís famous kite experiment led him to discover that lightening was electricity. In the early 1800ís, Michael Faraday added to this knowledge by discovering the relationship between electricity and magnetism. Joseph Henry soon revealed the nature of electromagnetic induction, which laid the foundation for numerous inventions such as the light bulb by Thomas Edison. Today, we continue to add to the list of inventions that depend on electricity.
Electricity flows along a path called a circuit. To create a circuit, you need a battery, wire, and a bulb. The electricity must be able to move from one end of the battery, through wires (including the wires in the bulb), and back to the other end of the battery in order to create a complete circuit. Like many things in nature, electricity is invisible, but we can see and measure the results of the flow. The actual flow of electricity through a circuit is called the electric current and is measured in amperes. By convention, scientists speak of the electric current in a circuit as though it flows from the positive end of the battery through the wires and back to the negative end of the battery. This convention arose due to Benjamin Franklinís theory that electric current was carried by positive charges. Franklinís theory has since been disproved, and we now know that either positive or negative charges can move through an electric current. In metals, however, the negatively charged electrons are the ones that move.
The battery, or energy source, gives electricity its "push" through a circuit. This "push," or voltage, can be thought of as electrical pressure and is measured in volts. The common one-celled batteries (AAA-, AA-, C-, and D-cells), with which the students will be working, differ in size and in the amount of current they provide. However, they all produce approximately 1.5 volts.
All light bulbs are essentially the same. The only significant difference between a household bulb and a miniature bulb is the length of the filament (the part that lights up). The filament of a household bulb is longer and thereby capable of producing a brighter light. (The large bulb also requires more voltage to light.) Regardless of the filamentís size, a wire from one side of the filament passes through the glass and connects to the threaded metal base of the bulb. A wire from the other side of the filament passes through the glass and connects to the metal tip at the bottom of the base. The metal tip is separated from the threaded metal base by a ceramic insulator.
Conductors and insulators are also important components in electric circuits. Conductors (usually metals) are materials that allow electricity to pass through them. If added to a circuit, electricity will continue to flow and the bulb will light. Insulators, on the other hand, are materials through which electricity cannot travel. If added to a circuit, insulators will stop the flow of electricity causing the bulb not to light. The classification of materials as conductors and insulators can get more complex. For example, there are materials called semiconductors that sometimes act as conductors and at other times act as insulators.
There are two kinds of circuits: series circuits and parallel circuits. In a series circuit, electricity has only one path to travel from one point on the circuit through the wires, batteries, and bulbs, and back to the starting point. When batteries are arranged in series, the voltage across the bulb is increased, causing the bulb to glow brighter than it did when only one battery was used. Unfortunately, the batteries will drain more quickly in such an arrangement. In a parallel circuit, electricity travels along more than one path around the circuit. When batteries are arranged in parallel, the brightness of the bulb will be the same as it was with one battery, but the bulb will burn longer in this circuit.
Bulbs can also be wired in series or parallel. When two identical bulbs are wired in series with one battery, they burn with uniform brightness, but are not as bright as one bulb alone. On the other hand, when two bulbs are wired in parallel with one battery, each bulb burns as brightly as a one bulb-one battery arrangement. One attribute of the parallel circuit is that unscrewing one bulb does not make the other bulb go out because the electricity travels in independent paths through each bulb.
Concepts Covered in the Lesson:
· "The paper clip lets the light bulb come on." (p. 50, #30)
· "If you put the plastic stuff in the circuit, the light bulb wonít come on." (p. 50, #30)
· "The stuff made of metal will complete the circuit." (p. 50, #30)
Materials & Equipment:
For each student
· a data chart on which the students can record both predictions and results
For every two students
· a circuit tester
· 1 package including the following objects:
-1 golf tee
-1 wooden pencil (with no eraser)
-1 paper clip
-1 piece of aluminum screening
-1 piece of plastic screening
-1 piece of chalk
-1 brass paper fastener
-1 piece of pipe cleaner
-1 piece of a straw
-1 piece of copper wire
-1 brass screw
-1 piece of aluminum wire
1. During the colloquium, I will ask several students to demonstrate the experiment
through creative drama. (One student will act as a battery, one will act as a light bulb, a third will act as either a conductor or insulator, and the last will act as the flow of electricity. Together, they will create a circuit in which the flow of electricity can continue if a conductor is present, but must stop at the presence of an insulator.)
2. Closure project: The students will write a short story that describes/explains the events of the experiment. [The story will be written from the electronís (flow of electricity) point of view as it explains what happens when it runs into an insulator.]
Useful Internet Resources:
Making an Electrical Circuit
· This lesson is an in-depth study of electrical circuits through various experiments.
Science Process Skills:
· Students will utilize techniques essential to scientific investigation (p. 46, #1).
-Demonstrating critical thinking
-Predicting possible results
· Students will exhibit habits necessary for responsible scientific investigation (p. 46, #2).
-Attention to detail
· Students will communicate scientific content effectively (p. 46, #3).
· Students will construct mental, verbal, or physical representations of ideas, objects, and events (p. 46, #4).
· Students will recognize the effects of manipulated and controlled factors on the outcomes of events (p. 46, #5).
· Students will demonstrate the appropriate use of instruments and procedures when learning new information (p. 46, #6).
Critique of Conductors and Insulators
I honestly believe that Conductors and Insulators was one of the most successful lessons that I taught during my internship. It was a hands-on lesson in which the students learned about conductors and insulators by testing various materials to determine whether or not they conducted electricity. Planned according to the Investigation-Colloquium method, I began the lesson by telling the students that they would be testing the items in their package to see whether or not each item could be part of a complete circuit. I quickly reminded the children that the bulb would glow if the circuit was complete. At this point, I let the students begin.
After making their predictions, each pair of students began to test the fourteen items. As I circulated around the room, I watched the anxious students as they either confirmed or disproved their predictions. Their enthusiasm was apparent in their wide eyes and smiling faces. I was obviously excited by their enthusiasm, but I was also impressed by the observations that they were making. I overhead several students talking about how they had figured out that the objects made of metal always made the light come on, but the others did not. When the students finished testing the packaged items, they began to test materials around their desk. I was thrilled to watch the children explore with their hair, skin, crayons, markers, erasers, binders, spiral notebooks, books, and clipboards. They were fascinated by their investigations, and it was obvious that they were proud of and eager to share their discoveries. Before calling the students to the front of the room for the colloquium, I watched one child open his binder. Realizing that only metals could complete the circuit, he touched the two free wires to a metal ring while exclaiming, "I knew it!"
During the colloquium, which lasted longer than I had anticipated, some of the students lost interest in the activity and began to talk with one another. This caused a slight disruption, and I was forced to stop the discussion so that I could speak to the talkative students in the back. I now realize that such a disruption could have been avoided had I not called the students to the front of the room for the colloquium. Rather, I should have let them remain seated at their desks. Had the children stayed at their desks, it would have been easier for me to make eye contact with each child, thereby making them more cautious of their actions. Also, the seating arrangement would have prevented good friends and/or troublemakers from sitting next to one another. Fortunately, I was able to separate the three boys, and the discussion continued without further disruption.
At the end of the colloquium, I chose three volunteers to participate in a creative drama. Using yarn to represent wire and two pieces of construction paper to make a large battery and light bulb, I had mapped out a circuit tester on the floor prior to the lesson. I assigned each child a role, made sure that each was in the correct place, and then told the actors to begin. Unfortunately, they all just stood there. I had to prompt Kacy, who represented the electron flow, to begin her path around the circuit. When she got to Trevor, the conductor, she stopped although she should have continued. After asking her if electrons could flow through conductors, she began to walk around the circuit. She continued to travel around the circuit, but Rhiannon, the light bulb, forgot to "light up." I stopped the drama and told Rhiannon that the light bulb should light up when the electrons reach it. Without thinking, I quickly threw my hands up in the air to signify a glow. Rhiannon did the same, and the drama continued.
To be honest, the drama did not go as well as I had hoped it would, but it certainly was not a disaster. Looking back upon this part of the lesson, however, I can think of a few ways to improve upon the creative drama. Rather than simply giving each child a role to play, telling each where to stand, and then expecting them to know what to do, I should have given the students more input. To begin with, I should have asked the class what would be needed if we were to build a complete circuit. As each part was mentioned, I would then choose an actor with whom I would briefly discuss his or her job as part of the complete circuit. I feel like this would have better prepared the students, thereby resulting in a more precise drama.
In conclusion, I feel like this was a very successful lesson. Although each part did not unfold exactly as I had planned, I still believe that it was a success. After all, the students learned about insulators and conductors, and they had fun while doing so. Most importantly, however, is the fact that the children were able to construct their own understandings of conductors and insulators while investigating and making their own discoveries.