Building an Electromagnet
Students will demonstrate how an electric current can make an iron object magnetic by building an electromagnet with a steel nail, insulated wire, a simple switch, a battery/cell, and small metal washers. Students predict the number of washers they can gather on the electromagnet and develop other possible ways to increase or decrease the strength of the electromagnet.
This activity is designed for students to understand that a relationship exists between electricity and magnetism, and the application of electromagnets to everyday uses. Key concepts include the following: whenever electricity flows through a wire, a magnetic field develops around that wire. When there is no flow of electricity flowing (as with an open circuit) the magnetic field is broken. The steel nail becomes a temporary magnet through induction. The vocabulary words induced-without direct contact, and load-the quantity or amount that is carried (or lifted in this case.)The term variable will be reviewed. Students will graph the relationship of the number of winds coiled around the steel nail to the number of washers lifted, and develop a conclusion based on their data.
Context for Use
This activity will be used in a fourth grade public school classroom of 30 students. The students will be grouped heterogeneously in 9-10 groups of 3 or 4 students per group. Skills that will be needed prior to this activity will be graphing and cooperative group roles established. This activity comes towards the end of our unit therefore making it harder to adapt to other settings because of the amount of concepts developed in previous lessons.
-Cell (battery) is a source of electric energy
-All metals are conductors
-An electric current is a pathway that electricity flows
-A closed circuit allows electricity to flow
-An open circuit (or an off switch) stops the flow of electricity
-Safety procedures are expected for all of hands-on activities.
Subject: Physics:Electricity & Magnetism
Resource Type: Activities:Lab Activity
Grade Level: Intermediate (3-5)
Description and Teaching Materials
This activity is adapted from the Foss Unit on Magnetism and Electricity Investigation 4 parts 1 and 2. Begin the lesson with a fictitious story about a giant who lives near the teacher's house who wants to bake cookies. He has all the things he needs except for cookie sheets made from metal. The cookie sheets are way too heavy for any person to carry, and the giant is quite particular and wants to be sure that the cookie sheets will not be crushed or dented by any forklifts or cranes that would pick them up. Tell the students to think about what they have learned in science so far to come up with some ideas. Have the students write or draw their idea in their science journals. Share ideas. A student may suggest a gigantic magnet. If so, ask how they would then get the cookie sheets off of this giant magnet if we can not use a machine to do so. Lead them to think how nice it would be to have a magnet that could be turned on and off. Ask students to write in their journals what materials were used so far in our unit to make energy flow. (a cell, and wires...some may say light bulbs or motors were the objects that used the electricity.) Ask what was used to stop the flow of electricity (a switch.) Have student put their journals away for the moment. With the whole class choose a child to show how a smaller substitute for the cookie sheets (some steel washers) could be picked up with a magnet. Next have the child pick up the steel nail with the magnet and use the nail to pick up the washers. The nail now has induced magnetism and will pick up the washers. Then have the child try using just the nail. This verifies that the nail alone can not pick up the washers. Have students think for a moment what you have just shown. Direct their attention to the materials area where you will have supplies for each group set on trays. Each group will need 1 nail, a 150cm length of 24 gauge wire, a 15cm length of 20 gauge wire, a D-cell, a switch, a plastic cup with about 50 small washers, and a circuit board. (The circuit boards we use are supplied with the Foss kit.) Show one of the trays. Have them notice that there is only one new material, the long wire, that has not been used in previous activities. With the groups that have already been established, have the supply person get the tray of materials and allow groups to explore possibilities. If students need some guidance to build the electromagnet, suggest that the long wire be wrapped around the nail, and that the wire must be in a circuit with the D-cell and switch. Share the various designs that groups built. Teacher note for accurate set up... The short wire is connected from the D-cell to the switch. The nail should be wrapped with the longer wire having the 2 loose ends. One of those ends connects to the switch, the other end is connected to the D-cell forming the circuit. Next have students determine standards for each electromagnet so that each group can compare results. Review the term variables and discuss the importance of having similar set ups. Discuss the importance of how the wire is wrapped around neatly on the nail with no overlapping sections. Have each group try their electromagnet and count how many washers they were able to pick up. Since no specific number of wraps were given, allow students to develop their own amounts. Share results of each group. Discuss why some groups may have been able to pick up more or less washers. Explain that you would like them to design an experiment showing on a graph what they have learned. Allow time to develop ideas. If guidance is needed suggest that the x-axis will represent the number of winds on the electromagnet, the y-axis will be the number of washers picked up by the electromagnet. Before any trails, have students write their prediction on a T-chart in their journals. After each trial record the actual number in the notes to be plotted on a graph once finished. Have students document their conclusion in their journals with their group. These results will be shared with the whole class to compare learning.
Teaching Notes and Tips
Some common areas of confusion are with the set up in general. In teaching this before, I showed how the electromagnets are constructed. I would not do that now, but just offer suggestions of using what they already know. Be sure to keep the switch open when the electromagnets are not being used because the batteries will drain quickly. I will also have the students document their ideas more often in their journals and develop and construct their own graphs possible during a math class if more time is needed.
Student journals will be selected randomly throughout the unit so that there are samples from each group. This will allow me to check individual's work. Group work can be assessed more informally by observation of class participation and contributions.
Physical Science Strand II.E.2
References and Resources