# Magnetism and Energy

In this unit, students connect their explorations of Earth and life sciences with physical sciences with an exploration into the science phenomena of magnetism and electricity. They investigate magnetic fields and electromagnets in this lesson. This page showcases key parts of this lesson.

## Science Background for Teachers:

Science background gives teachers more in-depth information on the phenomena students explore. Below is an excerpt from this section on magnetism and energy.

### Forces and Energy

Imagine you have two magnets. When they are within each other’s magnetic fields, they form a system because they interact with one another by exerting a force on each other. For example, if you orient the magnets so that their like poles are facing each other, they will repel, pushing away from each other.

Now imagine that you push those repelling magnets toward each other. You have to use energy to overcome that repelling force to move them together. As you push them, you apply a force to the system that transfers the energy from your hands into the system. In other words, your pushing force provides an input of kinetic energy into the system.

That input of kinetic energy is stored in the system as potential energy. You can see evidence of this potential energy when you let go of the two magnets and they move apart from one another. The potential energy stored in the system has been changed back into kinetic energy.

If you change the distance between the interacting magnets, you change how much energy is transferred into the system. For example, the closer you push two repelling magnets together, the more energy you need to use. This means more energy is transferred into and stored within the system. This will cause the magnets to move farther apart when you release them. In a perfect system, the total amount of energy is always conserved as it changes from one form to another. In other words, however much potential energy the system of interacting magnets has, that same amount of energy will change into kinetic energy as the magnets are released and move away from one another. However, in the real world, some of that energy is transferred out of the system. When energy is transferred, it moves into or out of an object or system. For example, if the magnets move across the ground, friction will transfer some of the energy out of the system. Friction is a force that slows motion whenever two objects rub against each other by causing some of the energy of the moving objects to change into heat.

### Kinds of Magnets

Whether an object is a magnet is one property of matter. An object has magnetic properties if its electrons are behaving in a specific way.

Remember that all matter is made of tiny particles called atoms. Atoms are made up of even smaller particles, including protons, neutrons, and electrons.

Protons and neutrons are found in the nucleus, and electrons orbit the nucleus at different distances called shells. Protons have a positive charge (+), and electrons have a negative charge (-).

In non-magnets, electrons randomly spin clockwise or counterclockwise. In contrast, magnets have electrons that mostly spin in the same direction.

People can cause objects to become magnetized. For example, if you repeatedly rub an iron-containing object, such as a paper clip or a nail, with an active magnet, it causes that object’s electrons to align temporarily.

Magnets can also be created with the use of electricity, the flow of electrons through a conductor. Electromagnets are tightly wound coils of wire that produce a magnetic field when electricity passes through the wire. They are useful in various technologies because the magnet can be turned off and on. This is different from permanent magnets, which stay magnetized without electricity.

### Electricity and Magnetism

Electricity is closely linked to magnetism. Charged particles change the space around them. They produce an electric field, which is the area around a charge that can exert a force on other charged particles. Similar to magnets, charged particles either attract or repel one another.

Particles that have an opposite charge attract one another within their electric field, while particles with the same charge repel each other within their electric field. Electrons are kept in orbit in their shells because the positive charge of the protons in the nucleus attracts the negatively charged electrons.

The strength of the field weakens with distance. Because of this, electrons in shells closest to the nucleus are tightly bound, while electrons in the outermost shell are much more loosely bound. When a force is applied, electrons in the outer shells can be pushed from one atom to another. Once that first electron has been pushed away from its atom, it moves to another atom.

This movement of electrons causes electrons to all move in the same direction as one another. Electrons can move more easily through some materials than others. Electric conductors are materials that allow electrons to pass through them easily. Metals such as copper and aluminum are electric conductors because they have electrons that are loosely held and therefore can easily be pushed from their shells by an outside force.

Electric insulators are materials that do not allow electrons to pass through easily because electrons do not easily separate from their atoms. Rubber and plastic are both good electric insulators. This is why electrical cords are covered in rubber or plastic. The electricity cannot travel through the rubber or plastic and is forced to follow the path on the aluminum or copper wires. Some materials are semiconductors, which means they can sometimes act as a conductor, depending on what other molecules are around.

## Science Lesson: Investigating Magnetism and Energy

In this lesson, students explore the phenomena of how magnets can exert a force on other magnets and magnetic materials without coming into contact with each other. They first investigate the relationship between the number of magnets in a system and the size of the magnetic field produced, and then investigate how the amount of potential energy stored within a system of interacting magnets can change when the distance between the magnets changes.

## Science Big Ideas

• Magnets are objects that produce a magnetic field. A magnetic field is the invisible area around a magnet that attracts or repels other magnets and magnetic materials such as iron.
• 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. Two south poles will also repel each other. The interactions of the two magnets depend on how each one is oriented relative to the other.
• A system of interacting objects can store different amounts of potential energy. Whenever objects interact, they form a system that energy can be transferred into or out of.
• Energy can be transferred into a system by a force, and the amount of energy a system can store depends on the amount of force applied to the system.

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## Science Essential Questions

• How do you know that magnets can exert a force on other magnets without coming into contact with them?
• Why do magnets sometimes attract each other and sometimes repel each other?
• How do the principles of magnetism explain how refrigerator magnets work?
• Where does gravitational potential energy come from?
• Why do two magnets form a system?
• How can you apply a force to the system of magnets?
• How do you think the application of force, either pushing or pulling, would affect the energy of the system of interacting magnets?

## Common Science Misconceptions

Misconception: All metals are attracted to magnets.

Fact: Metals attract some metals, including iron, nickel, and cobalt. However, many metals, including copper, silver, and gold, are not attracted to magnets.

## Science Vocabulary

Attract : to pull toward

Magnet : an object that produces a magnetic field

Magnetic field : the invisible area around a magnet that attracts or repels other magnets and magnetic materials such as iron

Repel : to push away

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

Navigating by Earth’s Magnetic Field

Dorothee Kremers is a scientist. She and a team of scientists were curious if bottle-nosed dolphins are able to sense magnets. Magnets are objects that produce a magnetic field. A magnetic field is the invisible area around a magnet that attracts or repels other magnets and magnetic materials such as iron.

Earth – A Giant Magnet

The reason scientists care about animals’ ability to sense magnetic fields is that Earth itself is a giant magnet. It has a magnetic field that is created in Earth’s liquid iron core and extends far into space. Scientists believe animals such as dolphins, sea turtles, bats, spiny lobsters, and many insects navigate from place to place using Earth’s magnetic field.

Understanding how Earth’s magnetic field could help animals navigate begins with the basic rules of magnetism. Magnets exert a force on other magnets or magnetic materials. A force is a push or pull that acts on an object, changing its speed, direction, or shape. Magnets either repel or attract other magnets or magnetic materials. To repel means to push away. To attract means to pull toward.

All magnets, including Earth itself, have a north pole and a south pole. (Earth’s magnetic north pole is actually near the South Pole, while its magnetic south pole is near the North Pole.) The north pole of one magnet always attracts the south pole of another. However, two north poles will always repel each other. Two south poles will also repel each other.

Magnetic Fields

One hypothesis about how animals navigate using Earth’s magnetic field is that they have tiny magnetic particles in their cells that react with Earth’s magnetic field, somehow signaling the nervous system in a way that guides the animals as they travel around the planet.

However, scientists cannot say for sure how animals use Earth’s magnetic field. The scientists who studied dolphins focused on one part of this question: Can dolphins sense magnets?

Dolphins Sense Magnets

Dorothee and her team set up an experiment with six dolphins. They set up two different kinds of barrels. One kind of barrel was made of a magnetic material. The other kind of barrel had an identical shape and density, but it was demagnetized. The scientists then videoed how the dolphins interacted with the different barrels. Their experiment showed that the dolphins swam toward the magnetized block much faster than they swam toward the demagnetized block.

The scientists still don’t know exactly how animals can sense magnetic fields. But they believe that animals in the ocean may benefit from having a magnetic sense that detects Earth's magnetic field. This is because the ocean is vast, with few landmarks that animals can use to mark their path. “Inside the ocean, the magnetic field would be a very good cue to navigate," Dorothee said in a 2014 interview with Live Science.

The experiment didn’t tell scientists that dolphins could sense Earth’s magnetic field. This is because the magnets used by the scientists had a much stronger magnetic field than Earth’s own magnetic field. More research needs to be done to explore whether dolphins can sense Earth’s weaker magnetic field, and if this is how dolphins navigate.

## Hands-on Science Activity

For the main hands-on activity of this lesson, students first create a model to explore the size of a magnetic field phenomena and then carry out an investigation to evaluate how the amount of potential energy stored in a system of repelling magnets can change depending on the position and configuration of the magnets. Students use their investigations to figure out how magnets are able to exert the phenomena of force on other magnets or magnetic materials without coming into contact with each other and how a system of interacting magnets can store different amounts of potential energy.

## 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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