Review the concept of electricity with the class. How is electricity created? How does it work? What is an electrical current? How does it travel? How do humans harness electricity from the Earth? A good way to review this topic is to watch Earth's Energy .
After watching the program, talk about electric current and the different types of circuits. How do these circuits work? What is the difference between a series and a parallel circuit? Divide students into groups of 2-3 and have each group make a simple circuit, a series circuit, and a parallel circuit.
Give each group a D-cell battery, battery holder, two pieces of electrical wire, a light bulb, and a light bulb holder. Give students the following directions to construct a simple circuit:
Ask students to describe what happens to the light bulb when all the wires are correctly attached. Explain that this is a simple circuit. Have students draw a diagram of a simple circuit in their science journals or on a piece of paper.
Give each student group a second light bulb and light bulb socket and two more pieces of wire and ask them to think about a way to light both bulbs at once. Have volunteers describe how they would go about creating a circuit that would light both bulbs at once. Discuss some of the hypotheses and have students test them out to see if they work. Then, explain that there are two different kinds of circuits that could be used, a series and a parallel circuit.
Use the following instructions to help students construct a series circuit:
Have students describe what happens to both light bulbs when the circuit is complete. Explain that in a series circuit, an electric current flows from the battery to one light bulb and then through to that bulb to another and, finally, back to the battery in one continuous loop, or circuit.
Next, have them hypothesize about what would happen if they loosened or disconnected one of the light bulbs in the circuit. After writing down their hypotheses, have them experiment with their circuit to see if they were correct. What happens when one of the light bulb sockets is loosened or released? Ask students to draw a diagram of their series circuit in their science journals or on a piece of paper.
Tell students they will next make a parallel circuit. What do they think is the difference between a parallel circuit and a series circuit? What do they think will happen if they loosen or release a light bulb in a parallel circuit?
To make a parallel circuit, begin with the simple circuit created earlier. (Remove bulbs from their sockets.) Once this is done, have students use the following instructions to complete their parallel circuits:
Explain that what they have just constructed is a parallel circuit; the electricity from the battery flows through two separate branches of the circuit to bring an equal amount of energy to the two bulbs. Have students compare the diagram they drew of a series circuit with this parallel circuit. How does the series circuit differ from the parallel circuit? (A series circuit has only one loop of energy as opposed to the branches created in a parallel circuit.) What do they think will happen if you loosen or release one of the light bulbs in a parallel circuit? Have student groups experiment with this and see what they find out. Have students draw a diagram of a parallel circuit in their science journals or on a piece of paper.
After students have demonstrated a clear understanding of parallel and series circuits, ask them to provide examples of parallel and series circuits they have used or seen being used. Some possible examples include: strings of Christmas lights (series), hydroelectricity from the Hoover Dam (parallel), and streetlights (parallel). Finally, discuss direct and alternating currents and talk about how we measure the flow of electricity.
If there is time, allow students to go online and learn more about electricity and electric circuits at the following Web site: http://www.andythelwell.com/blobz/(requires Macromedia Flash Player 6 or above)
ampere (amp)
Definition: Unit of measurement used to determine the amount of electric charge flowing past a given point each second.
Context: Trying to send too many amps through a circuit can cause a fire.
conductor
Definition: A material through which electric current flows easily
Context: Copper, aluminum, and iron are all good conductors of electricity.
circuit
Definition: The complete path of an electric current
Context: When an electric circuit is broken the current stops flowing.
direct current
Definition: Electric current that flows in one direction only
Context: Batteries produce direct current.
insulator
Definition: A material that opposes the flow of electric current
Context: Rubber, glass, and plastic are all good insulators.
voltage
Definition: The force that drives electrical charges through a circuit
Context: As voltage increases, so does the flow of energy.
National Academy of Sciences
The National Science Education Standards provide guidelines for teaching science as well as a coherent vision of what it means to be scientifically literate for students in grades K-12. To view the standards, visit this Web site: http://books.nap.edu/html/nses/html/overview.html#content.
This lesson plan addresses the following national standards:
Mid-continent Research for Education and Learning (McREL)
McREL's Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education addresses 14 content areas. To view the standards and benchmarks, visithttp://www.mcrel.org/compendium/browse.asp
This lesson plan addresses the following national standards: