Electricity

Build an electric motor

Explore how the relationship between electricity and magnetism work to power an electric motor.

Grade 7
Hands On
1 hour

BC Hydro

Overview

In the same way that electrical current creates a magnetic field, the reverse is also true. In this activity, your students will build electric motors that are enabled by magnets. This hands-on experience has real-world application, as all electric motors in our lives come from this basic principle.

What you'll need

Each group will need:

Tape
Large markers
“Build an electric motor” worksheets for each student
120 cm of enameled wire
Sandpaper
2 dry cells (batteries) and holders
2 wires with alligator clips
1 ceramic magnet
2 large paper clips

Instructions

It’s a good idea to build your own electric motor in advance so you know how to do the activity and you can work through the troubleshooting steps.

Safety first

Ceramic magnets are powerful and can damage electronic equipment. Keep them away from all devices like smartphones, tablets, and computers.
Metal components in the circuit you are building will get warm during the activity, so don’t touch the batteries, alligator clips, coil, or paper clips.
Remember to disconnect the wire after each observation.

Building the electric motor

Put your students into groups of two or three and then have them follow the following steps:

Students need to create a coil by wrapping the wire tightly around the marker about 20 times; they should have 6 cm of wire sticking out at each end.

Then they should loosen the coil slightly and remove it from the marker. To keep the coil from unravelling, have students twist each wire end around one side of the coil.

Students can use sandpaper to scrape away the coating at both ends, exposing about 2 cm of wire.

Next, students should bend the paper clips to create holders for the coil. Tape can be used to secure the paper clips to the table, and the ends of the coil should be stuck out through the loops in the paper clips. The paper clip loops must be level so the coil can spin.
Students can then connect the alligator clips to the batteries and paper clip holders as shown here. Note that once the clips are connected, electricity is flowing through the circuit. Students may need to help the coil start spinning:

Troubleshooting the electric motors

If the coil doesn’t spin, here are some things students can try:

Make sure that the loops of the paper clip holders are level so the coil is balanced and can spin freely.
The coil needs to be over the magnet for the motor to work properly. Try moving the coil or moving the magnet so the two are lined up.
Check the circuit’s connections. The paper clips need to be touching the exposed ends of the coil wire or electricity cannot flow.
Make sure that the batteries have power in them. Use a light bulb to check.

Document and debrief

Make sure your students make observations on their "Build an electric motor" worksheet and that they complete the analysis.

Have the groups share their experience creating an electric motor. Students can talk about what they found challenging, how they solved problems, and what success looked like.

Additional Information

Assessing your students

Use the "Electricity and magnetism: curricular competencies assessment" to make note of your students skills with group work
Review the "Build an electric motor: competencies self-assessment" completed by students
Use the "Build an electric motor" answer key in the teaching notes below to assess written work

Modify or extend this activity

Students can test different variables that affect the way an electric motor works, including:

The number of coils
The shape of the coil; oval versus round, for example
The amount of power, here determined by the number and size of batteries
The position of the magnet

Notes to help you teach

Moving electrons (electricity) generate a magnetic field around a wire, and the reverse is also true: moving magnets through coils of wire generates electricity. This is how electricity and magnetism work: the movement of one causes the other.
One wire with electricity flowing through it creates a magnetic field. The more loops in the coil, the stronger the force of the magnetic field when an electrical current passes through it. In this activity the loop has 20 coils.
The magnetic field created around the coil of wire has a north and a south pole, just like all magnets. When a magnet is placed underneath the coil, the like poles of the magnet will repel the like poles of the magnetic field around the wire at the same time as the opposite poles attract each other. This is what causes the coil to keep spinning.
Note: Ceramic magnets are used instead of bar magnets as they have a much stronger field that is oriented north/south on opposite sides, unlike the traditional bar magnetics with north/south on opposite ends.

"Building an electric motor" worksheet answer key:

Observations

Describe what you see. Include sketches as necessary.

The coil spins rapidly.
The coil spins for a short time and then stops.

What do you hear?

The coil spins so fast that it is making a sound as it rotates.

How long did your coil spin? What would make it stop?

Answers will vary. Answers could include: The circuit is opened or broken; the batteries run out of power; an object obstructs the coil; etc.

Analysis and conclusions

Using your understanding of electricity and magnetism, explain in your own words what is happening in the circuit to make the coil spin.

The wire has electricity flowing through it. This creates a magnetic field around the wire. Each of the coils of wire has a separate magnetic field around it so the coil has a strong magnetic field with a north and a south pole.
The magnet underneath the coil of wire also has a strong magnetic field.
The like poles of the magnet and the coil repel each other while the opposite poles attract each other. This causes the coil to spin.

What questions about electromagnetism do you have after today’s activity?

Questions will vary

How does this fit into the curriculum?

Grade 7 Science - Content

Electromagnetism

Grade 7 Science - Curricular Competencies

Questioning and predicting

Demonstrate a sustained intellectual curiosity about a scientific topic or problem of personal interest
Identify a question to an answer or a problem to solve through scientific inquiry

Planning and conducting

Collaboratively plan a range of investigation types, including field work and experiments, to answer their questions or to solve problems they have identified
Ensure that safety and ethical guidelines are followed in their investigations

Processing and analyzing

Use scientific understanding to identify relationships and draw conclusions

Applying and innovating

Co-operatively design projects

Communicating

Communicate ideas, findings and solutions to problems

Grade 7 Applied Design, Skills and Technologies - Content

Power technology
Forms of energy
Devices that transform energy

Grade 7 Applied Design, Skills and Technologies - Curricular Competencies

Protyping

Construct a first version of the product or a prototype, as appropriate, making changes to tools, materials, and procedures as needed
Identify a question to an answer or a problem to solve through scientific inquiry