Elementary | Formative Assessment Probe
By Page Keeley
Assessment Physical Science Elementary Grade 4
This is the new updated edition of the first book in the bestselling Uncovering Student Ideas in Science series. Like the first edition of volume 1, this book helps pinpoint what your students know (or think they know) so you can monitor their learning and adjust your teaching accordingly. Loaded with classroom-friendly features you can use immediately, the book includes 25 “probes”—brief, easily administered formative assessments designed to understand your students’ thinking about 60 core science concepts.
The purpose of this assessment probe is to elicit students’ ideas about complete circuits involving lightbulbs. The probe reveals whether students recognize the pathway of electricity in a complete circuit, including its path through a lightbulb, in order to light a bulb using only one strip of wire and a battery.
P-E-O
complete circuit, electricity
The best answer is A: One strip of wire. If you closely examine a flashlight bulb, you will see two small wires sticking up in the bulb that are connected by a very fine wire called a filament. The two wires on either side of the filament extend downward into the base of the bulb where you cannot see them through the metal casing that surrounds the base of the bulb. One of these wires goes down to the very bottom of the base (the pointed end). The other wire is connected to the side of the metal base (sometimes the side is ridged so that it can screw into a socket). Knowing where these wires end up on the base of the bulb (the tip and the side) is necessary in order to use one wire to make a circuit that lights a bulb.
The battery, wire, and bulb need to be connected in such a way that it forms a complete circuit. To do this, hold the end of the wire against the negative terminal (the bottom of the battery or smooth end). The other end of the wire should touch or wrap around the side of the metal casing that forms the base of the lightbulb. With the wire wrapped around the metal side of the bulb and the other end touching the bottom of the battery, touch the tip of the base of the lightbulb to the positive terminal (bumpy end) and the bulb will light.
The lightbulb lights with just one wire because the electricity flows out of the negative terminal (bottom of the battery), through the wire, into the wire that is attached to the side of the metal casing on the base of the bulb, up through that wire inside the bulb, across the filament, and down the other wire inside the bulb where it is attached to the point on the base of the bulb that touches the positive terminal (the bump) of the battery, completing a full circuit.
Be aware, however, that students can choose the best answer, “one wire,” and still have an incorrect configuration of a circuit. For example, some students may touch one end of the wire to the battery and the other to the bulb, thinking the energy from the battery will flow through the wire to the bulb. Students who choose two wires as their answer may understand that a complete circuit is needed, but not understand the internal architecture of a lightbulb.
Elementary Students
“Batteries and bulbs” is a common instructional topic found in elementary school curriculum materials that help students acquire skills of inquiry while learning what a complete circuit is and about the architecture of a lightbulb. Building complete circuits is primarily observational at this level and provides students with an opportunity to systematically test out their ideas and make observations.
Middle School Students
In middle school, students build a variety of different circuits to trace the path of electricity. At this level, they are able to understand why the lightbulb is designed the way it is in order to build a circuit. They also begin to build an understanding of the direction in which the electric current flows. Students build on their earlier experiences with complete circuits to understand the transfer of energy that is involved in a circuit designed to accomplish a task such as lighting a lightbulb.
High School Students
Students at the high school level have begun the study of particles smaller than atoms, and their study may begin to link particles such as electrons to the notion of charge and to ideas of current and electric circuits. However, it is important to remember that many students may have had little experience with electric circuits themselves or that their experiences involved prefabricated circuit boards and light sockets that prevent them from seeing how the current flows through a lightbulb.
Make sure students know what you mean by a “strip” of wire. Show them a battery, a bulb, and a coil of wire. Cut a strip off that is long enough to make the circuit so they know what is meant by a strip of wire. Or, show a handful of cut strips, but do not show just one, because it might cue them to the answer. Note that if students choose more than one wire, it is not necessarily incorrect in terms of making a complete circuit. However the probe is not asking how many wires are needed to make a complete circuit but rather what the minimum number of wires is. It is important to emphasize drawing as a way of supporting the students’ explanation in this probe.
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