# Magnets and Motors

In this unit, students explore the science phenomenon of electric currents and electrical energy. In this lesson, students figure out energy transfers, electricity, and circuits in the context of an electromagnetic motor system. This page showcases each key section of this lesson.

## Science Background for Teachers:

Science background gives teachers more in-depth information about the phenomena students explore in this unit. Here is an excerpt of the science background information for this lesson on magnets and motors.

Electric current produces a magnetic field when negatively charged electrons in a conductor move in the same direction. That movement produces a magnetic field around the conductor, which attracts or repels other magnets and objects that contain iron or steel.

All magnets have two magnetic poles—a north pole and a south pole. The rules of magnetism are that opposite poles attract and like poles repel. This means that the north pole of one magnet always attracts the south pole of another, but two north poles always repel each other, as do two south poles.

Magnets are useful in many different applications because they can attract or repel other objects without touching. There are different kinds of magnets. Permanent magnets are objects that stay magnetized without electricity.

Natural magnets are magnetized rocks. Temporary magnets act like a permanent magnet when they are within a strong magnetic field. They lose their magnetism when the magnetic field goes away. Paperclips and iron nails are temporary magnets.

Finally, electromagnets are tightly wound coils of wire that produce a magnetic field when electricity passes through the wire. That electricity is produced in a circuit.

The magnetic field around a straight wire is not very strong. However, if the wire is wrapped in a coil, each turn of the coil produces a magnetic field. The magnetic field of each coil combines to create a strong magnetic field when electricity passes through the coil. Electromagnets are useful because the magnet can be turned off and on by switching the circuit off or on.

Electromagnets are the key to how doorbells work. A simple analog doorbell often includes a battery, wires, an electromagnet connected to a magnetic clapper, and something that makes noise, such as a bell. When you push the doorbell’s button, you close the circuit. This closing of the circuit causes electricity to flow through the doorbell system, which magnetizes the electromagnet and produces a magnetic field around the electromagnet. This magnetic field pulls on the magnetic clapper, causing it to strike the bell. This is what makes the doorbell’s noise. The movement of the clapper striking the bell also opens the circuit. This stops the flow of electricity. As a result, the electromagnet is no longer magnetized.

Magnets are part of many electronic devices because they are used to drive small motors. A motor is a machine that transfers an input of energy into an output of kinetic energy. In an electromagnetic motor, electrical energy is transferred into kinetic energy. A basic electromagnetic motor has two parts: a permanent magnet and an electromagnet. The electromagnet becomes magnetized when it is connected to an electrical current. It then spins rapidly because it is surrounded by the permanent magnet. If a gear is attached to the spinning electromagnet, the gear can be made to do work.

## Science Lesson: Exploring Magnets and Motors

Once students understand how electricity can be transferred through a circuit, they focus on interactions between the phenomena of electricity and magnetism. Students figure out how to create an electromagnetic motor system that transfers electric energy and converts energy from one form to another.

## Science Big Ideas

• Magnets are useful because they can attract or repel (push apart) other objects without touching.
• All magnets have a north pole and a south pole. The north pole of one magnet always attracts the south pole of another. This means the two magnets are pulled together.
• There are two different kinds of magnets: permanent magnets and electromagnets.
• Permanent magnets stay magnetized without electricity. Electromagnets are tightly wound coils of wire that produce a magnetic field when electricity passes through the wire.
• A motor is a machine that transfers an input of energy into an output of kinetic energy.
• Magnets can be natural, temporary, or permanent. Electrical currents create magnetic fields around the conductors the electricity flows through.

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## Science Essential Questions

• How are magnets attracted or repelled from one another magnet?
• Why can it be useful to know how magnets interact?
• Where have you seen permanent magnets or electromagnets?
• How are electromagnets different from permanent magnets?
• Why is electricity able to magnetize an electromagnet?
• Why are electromagnets made up of coils of wire, rather than just a straight wire?
• How can electromagnets be more useful than permanent magnets?
• Why would an electromagnetic motor have two parts: a permanent magnet and an electromagnet?

## Common Science Misconceptions

Misconception: Batteries create electricity.
Fact: Batteries provide the force that pushes electrons through a conductor. When electrons move through a conductor, it produces electricity.
Misconception: Conductive wires are hollow so that electricity can flow through them.
Fact: Like all matter, conductive wires are made up of atoms that have electrons. These electrons just need a force applied, such as a push from a battery, to begin to move from one atom to another.

## Science Vocabulary

Circuit : the circular path electrons travel in a negative to positive direction

Current :  a measure of the rate that electric charge passes through a point in an electric circuit over time; measured in amps

Electricity :  the flow of electrons through a conductor 4. electric conductor – a material that electrons can easily pass through

Electric Insulator :  a material that electrons cannot pass through easily

Electromagnet :  a tightly wound coil of wire that produces a magnetic field when electricity passes through the wire

Motor :  a machine that converts an input of energy into an output of kinetic energy

Permanent Magnet :  an object that stays magnetized without electricity

## Lexile(R) Certified Non-Fiction Science Reading (Excerpt)

Ringing the Doorbell

When you go to someone else’s house, the first thing you often do is ring the doorbell. A simple push on a small button sends electricity that powers a sound to the inside of the house. This lets people inside know someone is at the door.

Doorbells work because they use a special kind of magnet. Magnets are useful because they can attract or repel (push apart) other objects without touching.

All magnets have a north pole and a south pole. The north pole of one magnet always attracts the south pole of another. However, two north poles will always repel each other, as will two south poles. This is why magnets attract some magnetic objects and repel others.

Kinds of Magnets

There are different kinds of magnets. Permanent magnets stay magnetized without electricity. Natural magnets are magnetized rocks. Temporary magnets act like a permanent magnet when they are within a strong magnetic field. They lose their magnetism when the magnetic field goes away. Paperclips and iron nails are temporary magnets.

Finally, electromagnets are tightly wound coils of wire that produce a magnetic field when electricity passes through the wire.

Electromagnets

Electromagnets become magnetized when electricity moves through the wire. This is because electric current produces a magnetic field. Remember that all of the electrons in a conductor move in the same direction as one another. This produces a magnetic field around the wire. A magnetic field is the area around a magnet that attracts or repels other magnets or objects that contain iron or steel.

The magnetic field around a straight wire isn’t very strong. However, if the wire is wrapped in a coil, each turn of the coil produces a magnetic field. The magnetic field of each coil combines to create a strong magnetic field when electricity passes through the coil. Electromagnets are useful because the magnet can be turned off by switching the circuit off. It can be turned on by switching the circuit on.

Motors

Magnets are part of many electronic devices because they are used to drive small motors. A motor is a machine that transfers an input of energy into an output of kinetic energy.

In an electromagnetic motor, electrical energy is converted into kinetic energy. The electromagnetic motor has two parts: an outside permanent magnet and an inside electromagnet. The electromagnet becomes magnetized when it is connected to an electrical current. It then spins rapidly because it is surrounded by the permanent magnet. If a gear is attached to the spinning electromagnet, the gear can be made to do work.

## Hands-on Science Activity

In this lesson, students figure out how to use phenomena produced by permanent magnets and electromagnets to create an electromagnetic motor system that transfers electric energy and converts energy from one form to another. Students use their prototype electromagnetic motor system to analyze how energy can be converted from one form to another to produce a spinning phenomena.

## Science Assessments

KnowAtom incorporates formative and summative assessments designed to make students thinking visible for deeper student-centered learning.

• Vocabulary Check
• Lab Checkpoints
• Concept Check Assessment
• Concept Map Assessment
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