Making an electromagnet
Grade level(s):Elementary School (K-5), Middle School (6-8), Grade 4, Grade 5, Grade 6, Grade 7, Grade 8
Topic:Electricity and Magnetism
Electric current flowing through a wire produces a magnetic field. A core of steel or iron becomes an electromagnet when electricity flows through a coil of insulated wire surrounding the core. The magnetism produced by an electromagnet can be turned on and off.
electricity, electric current, magnetism, magnetic field, insulator, variable, electromagnet,
What you need:
SEP Resource Center items: E 434 Electromagnet sets, E 438 or E 485 Battery holders, E 486 Batteries, E 430 Detecting magnetic fields
Wires of different length, alligator clips, battery holder, D batteries, cores for electromagnet made of different materials (iron, copper, wood, plastic), paper clips, compass,
One 60 minutes class period - Creating simple electromagnet (10 min.) - Determining variables to vary strength of electromagnet.(10 min.) - Creating the strongest possible electromagnet (20 min.) - Sharing results (10 min.) - Wrap-up (10 min.)
Students discover that, when electric current flows through an insulated wire wound around a steel core, the steel core becomes a magnet. They learn that this happens because an electric current produces a magnetic field. They experiment with a number of variables and try to find out how to increase the strength of the electromagnet.
Students know that electricity is the flow of electrons through a conductor (metal). Students know to to build basic electric circuits.
Students will be able to build a simple electromagnet. Students will be able to manipulate a variety of variables to increase the strength of the electromagnet.
An electromagnet is a magnet that can be turned on and off with a switch. A junkjard crane that picks up a big jumble of scrap metal and deposits it in a railroad car uses an electromagnet. The most common way to make an electromagnet is by winding insulated wire around an iron core, such as a bolt, nails, or railroad spike. When the wire is connected to a source of electricity, and the circuit is closed, electricity flows through the wire, and the core becomes a magnet. When the circuit is open, the electricity stops flowing, and the magnetism disappears. Whenever an electric current flows through a wire, a magnetic field develops around that wire. When the electricity stops flowing, the field collapses. There are several ways to increase the strength of an electromagnet. Additional winds of wire increase the strength of the magnetism. Inserting a second battery into the circuit in series with the first one also increases the strength. The larger the diameter of the wire, the stronger the magnet, given the same number of winds.
- Strip about two cm of plastic insulation from the wires pieces. - Check batteries to make sure they are all charged up. - Assemble trays or boxes for each group, containing all required materials. Put on lab benches for students to pick up after instructions are given.
Lesson Implementation / Outline
Show short clip of junkyard crane picking up and dumping off cars. Ask how that could work. Ask how that magnet is different to magnets students have been working with during the past few days (can be turned off). Tell students that they will build an electromagnet today.
1. Students build a simple electromagnet. Students will use their materials to build an electromagnet. Give students time to try to figure it out on their own, using their prior knowledge. Make suggestions and support where needed. Stop class and model assembly of electromagnet.
2. Determine variables. Brainstorm with students what variables you can change when building the electromagnet. Have student use handout (see attachment), or have them write their variables on sticky notes. Students report out their ideas. Collect answers on overhead or blackboard or have student post their sticky notes on pre-made poster. That way all students have a variety of variable to choose from for their investigation.
3. Determine how variable change the strength of the electromagnet. Have students pick one variable and experiment how manipulating the variable changes the strength of the electromagnet (how many paperclips can be picked up?). Stress the importance of multiple trials and fair tests.
4. Students graph their results. Depending on age you need to scaffold this part a bit more.
5. Students report out their findings to whole class.
6. If time allows, have students build the strongest possible electromagnet by changing several variables at once.
Have students quick write in their lab journals, answering the following questions: 1. How can you make a simple electromagnet? 2. How can you make it stronger?
Extensions and Reflections
Make sure to pass out materials AFTER you give instructions to keep their attention.
|Student worksheet - Designing an investigation.doc||28 KB|
|Designing an investigation- example responses.doc||29 KB|