Electric Motor

Your Activity Build a simple electric motor

Material D-Cell Battery 1 Rubber Band Coil made out of magnet wire Ceramic Magnet 2 Jumbo Safety Pins Dry Erase Marker (or Paper Clips) (or Nail Polish) Scissors (or sand paper) Card Stock Paper

Create

1. Observe the coil. This is going to be the thing that moves. It is made up of copper wire. 2. Carefully scrape off the insulation off one half of the coil axle on each side using the scissor / sand paper. 3. Coat top half of the axle with nail polish. 4. Attach safety pin (or paper clips) on each side of the battery using a rubber band. These safety pins will be the support the coil. 5. Place the battery on top of the table. Put a magnet on top of the battery. Insert the coil in the safety pin holder (or stand made out of the paper clips). 6. Insert a paper strip on one side of the battery—this will be the switch to turn your motor on and off. 7. Take the paper off of the battery to start the motor. What happens?

Science Topics Electrical Engineering, Electricity

What’s going on? Look around you… motors are used in an unlimited number of everyday devices designed by engineers. Engineers must fully understand and apply the connection between electricity and magnetism as they design and build motors, or design better and more efficient motors. To understand how an electric motor works, the key is to understand how the electromagnet works. An electric motor uses electrical energy to produce movement or mechanical energy. Motion is produced by the attractive and repulsive force associated with the poles of the magnets. The attraction and repulsion of the poles on the two magnets causes the electromagnet to begin rotating so as to align the opposite poles in the magnetic field. As it rotates, the electromagnet spins an axle, or armature, that performs the work of the electric motor.

Electric Motor

Activity Lead Notes

Introduction

Students investigate motors and electromagnets as they construct their own simple electric motors using batteries, magnets, paper clips and wire.

Today we are going to learn a little bit about how motors work. Engineers design motors for many different uses. Motors take electrical energy, and convert it into mechanical or moving energy. Basically, motors take the electrical energy from an electricity source, such as an outlet or battery, and change that energy into something that spins, moves or does some sort of work. We interact with all sorts of motors every day. Can anyone think of some different items that have motors?

Have you ever felt the force pushing or pulling between two magnets? What happens when you put two magnets next to each other? Sometimes they stick together quickly and sometimes they push each other away. Sometimes, the magnets actually move around and then stick together. When two magnets pull together, it is because one magnet wants to align its south pole (S) with the north pole (N) of another magnet. Engineers use this magnetic force to get motors to work.

Do you know the difference between an electromagnet and a permanent magnet? Well, one difference is that the magnetic field of an electromagnet can be turned on and off by turning on or off the source of electricity to the coiled wire. Many of the magnets used in machines are actually electromagnets rather than permanent magnets. However, even though we call them "permanent," permanent magnets are not really permanent either. They can be de- magnetized by hitting them with a hammer or heating them up.

The motor that we are going to build today has three parts: a permanent magnet, a coil of wire and a battery. Something that is really important to remember is that when electricity moves through a wire, it turns the wire into an electromagnet. So, our wire coil is going to eventually act like another magnet (when we run current from the battery through it). Our simple motor will really have two magnets, and they are going to work together to create movement by pushing and pulling on each other. Building motors can be kind of tricky, and engineers must learn a lot about magnetism and electricity to get them to work. Let's get started!

Learning Objectives

After this activity, students should be able to:  Create a simple motor  Describe how a motor uses an electromagnet and magnetic forces to work  Explain that motors are designed by engineers for use in various applications Materials Each student/group of students need:

 1 D-cell battery  1 wide rubber band  2 large paper clips (metal, without a coating)  1 rectangular-shaped ceramic magnet (available large hardware stores such as Home Depot)  43.5 in. (111 cm) medium-gauge magnet wire (Magnet wire is copper wire insulated with a polymer-based film, or red enamel, not plastic; available large hardware or electronics stores such as Radio Shack)

For the entire class to share:

 Fine sandpaper  Wire cutters  A few compasses (optional)  Thread Preparing Materials  Before starting the activity, show examples of motors to the kids (e.g. a toy car, circuit with radio shack motor, etc.).  Cut one, two-foot piece of magnet wire for each team  (Optional) you may want to create the coil yourself depending on the age group

Notes about Materials  Ask students to be very careful when using the sharp wire strippers and wire cutters.  Ask students to not play with the insulated wire; they might poke or cut themselves or another student.

Vocabulary Battery: A cell that provides electric current. Commutator: A cylindrical arrangement of metal bars connected to the coils of a DC (direct current) motor that provides for a reversal of current into the coils of the motor with every half spin, allowing the motor to spin continuously in one direction. Current: A flow of electrons. Engineer: A person who applies scientific and mathematical principles to creative and practical purposes such as the design, manufacture and operation of efficient and economical structures, machines, processes and systems. Insulated wire: Wire that is covered with a coating of some kind. Magnet: Something that attracts iron and generates a magnetic field. Magnetic field: The field generated by a magnet or by an electric current. Motor: An electrical device that converts electrical energy into mechanical energy. North pole: The end of a magnet that points north. Solenoid: A coil of insulated wire. South pole: The end of a magnet that points south. Uninsulated wire: Wire that is not covered with a coating

Background Electric motors are devices that convert electrical energy into mechanical energy (electricity into motion). Everyday we are surrounded by electric motors. In cars, for example, there are dozens of electric motors — rolling up the windows, wiping the windshield, adjusting the seats and side-view mirrors, starting the engine when the key is turned, and even a motor connected in reverse to recharge the battery when the car is moving. There are electric motors in your washing machine, refrigerator, blender, can-opener, computer, and all over your home, and they all work on the same basic principle. If you have ever played with magnets, then you have felt the force associated with magnetic fields. This force is always working to align the fields of the two magnets. A magnet wants to align its south pole (S) with the north pole (N) of another magnet. This is like the famous saying, "opposites attract." Harnessing this magnetic force is how we make motors work.

The motor in this activity consists of three parts: a ceramic magnet, a solenoid electromagnet (a coil of wire) and a battery. When there is current in the wire coil, it produces a magnetic field. One face of the coil becomes a north pole, and the other becomes a south pole. The ceramic magnet attracts its opposite pole on the coil and repels its like pole, causing the coil to rotate. The commutator and brushes of a typical motor are not required for this motor. Instead, half of the insulation is removed on one end of the wire. This means that for half of each spin there is no current in the wire. Therefore, the electromagnet cannot produce a magnetic field for that half spin. As the pole of the electromagnet comes closest to the permanent magnet, the insulated part of the wire turns off the electric current. However, the inertia of the rotating coil carries it through half of a turn, past the insulation. When the uninsulated part of the wire makes contact again, there is an electric current through the coil again. This produces a magnetic field that is in the same direction as when the coil was previously in the same orientation. Therefore, the twisting force on the coil is in the same direction as it was before and the coil rotates in the same direction. That is why this motor requires a push to get started, unlike a typical motor.

Activity Sheet Student Instruction Handout (from TeachEngineering.org)

Conduct Experiment  Kids use the procedure in the handout to create the motor.

Discuss student observations  Engineers design many things using electromagnets and motors. What are some examples of items engineers have designed that have motors? (Possible answers: Fan, blender, washing machine, dryer, CD player, electronic toys that move, etc.)  Which of these (appliances/equipment/devices) might require the most powerful motor? Why? (Answer: Any machine that has to move a heavy load, such as a washing machine, requires a more powerful motor than machines that move small loads, such as an electric can opener. Accept reasonable answers.)  What parts of the motor should engineers change to build more powerful motors? (Answer: The electromagnet, since the engineers can change the amount of electrical current in an electromagnet as well as the number of coils. The permanent magnet does not have those options for changing.)  If you were an engineer who was deigning a motor for a new electronic toy, what things would you consider in designing your motor? (Possible answers: How much the motor needs to turn, how big the motor should be, how much work the motor needs to perform, etc.)  What is making the coil spin? (Answer: The magnetic field of the electromagnet [the coil] is interacting with the magnetic field of the ceramic magnet, rotating the coil.)  Which part of the motor is the electromagnet? (Answer: The coil.)

Activity Extensions  Have the students experiment with coils of various shapes (but with the same number of wire wraps): oval, rectangular and square. Which shape spins the fastest?

 Have the students vary the number of wire wraps in the coil. Try a number less than seven. How about more than seven? Does the number of wraps affect the motor's speed?  Have the students investigate how the thickness of the wire affects the motor? (If the wire is too thin, it might not be able to pick up paper clips without bending. If it is too thick, it might be too rigid and not get good contact with the cradles.  Have the student change the design of the paper clip cradles. They might want to try smaller paper clips, more rubber bands, bending the paper clips completely differently or even sanding their surfaces for better contact.  Have the students use a ring-shaped magnet instead of a rectangular-shaped magnet. Does the shape of the magnet matter?  Have the students change one or more variables from the suggested changes in the extension activities and suggest a design for the best motor possible.

Simple Electric Motor