Science · 8th Grade · Forces, Motion, and Interactions · Weeks 1-9

Electromagnets and Their Uses

Students will investigate the relationship between electricity and magnetism by constructing and testing electromagnets.

• Common Core State Standards
• MS-PS2-5

About This Topic

Electromagnetism is one of physics' most powerful unifying concepts: an electric current produces a magnetic field, and a changing magnetic field produces an electric current. Students in US 8th-grade science build and test simple electromagnets to observe this directly, using a wire-wrapped iron nail connected to a battery to pick up paper clips or compass needles.

The strength of an electromagnet can be increased by adding more coils of wire around the core, increasing the current, or using a ferromagnetic core (like iron) instead of air. These factors are directly testable in a classroom lab, making electromagnets ideal for controlled experimental design at the 8th-grade level. Real-world applications include electric motors, MRI machines, speakers, and maglev trains, giving students multiple entry points for seeing the concept in use.

Active learning fits this topic particularly well because the variables affecting electromagnet strength are easy to isolate experimentally. Student groups can each test a different variable while sharing results, demonstrating how the scientific community builds knowledge through distributed investigation. Connecting lab findings to engineering applications grounds the abstract relationship between electricity and magnetism in recognizable technology.

Key Questions

1. Explain how an electric current can create a magnetic field.
2. Analyze the factors that affect the strength of an electromagnet.
3. Design an electromagnet for a specific application.

Learning Objectives

• Explain how the movement of electric charges creates a magnetic field.
• Analyze the relationship between the number of wire coils, the current, and the strength of an electromagnet.
• Design and construct a simple electromagnet to perform a specific task, such as picking up a target number of paper clips.
• Compare the magnetic field strength of electromagnets with varying core materials.

Before You Start

Basic Electric Circuits

Why: Students need to understand how to connect a battery, wire, and switch to create a closed circuit for current to flow.

Introduction to Magnetism

Why: Familiarity with basic magnetic properties, like poles and attraction/repulsion, is helpful before exploring electromagnetism.

Key Vocabulary

Electromagnetism	The interaction of electric currents or fields and magnetic fields. It is the basis for how electromagnets work.
Electromagnet	A temporary magnet created when an electric current flows through a wire coiled around a ferromagnetic core, like iron.
Magnetic Field	The region around a magnetic material or a moving electric charge within which the force of magnetism acts.
Ferromagnetic Core	A material, such as iron, that is strongly attracted to magnets and can be magnetized itself, significantly increasing the strength of an electromagnet.

Watch Out for These Misconceptions

Common Misconception

Students think electromagnets work the same way as permanent magnets in all respects.

What to Teach Instead

Electromagnets can be switched on and off by controlling the current, and their strength can be varied -- both things a permanent magnet cannot do. Having students try to turn off a permanent magnet (impossible) and then flip a switch to deactivate their electromagnet makes this contrast concrete and memorable.

Common Misconception

Students believe that adding more batteries always makes the electromagnet proportionally stronger without limit.

What to Teach Instead

Beyond a certain current, adding more voltage causes excessive heat in the wire and can damage the core's magnetic properties. Students who over-battery their electromagnets in lab often notice reduced performance -- a real data point worth discussing. Electromagnetic saturation is a real engineering constraint.

Common Misconception

Students think only iron cores work in electromagnets.

What to Teach Instead

Any ferromagnetic material (iron, nickel, cobalt) works as a core, and a coil of wire with no core at all is still an electromagnet (just a weaker one). Testing a nail vs. a plastic pen vs. no core in the lab directly challenges this assumption with evidence.

Active Learning Ideas

Lab Investigation: Building and Testing an Electromagnet

Student groups wrap varying numbers of coils of insulated wire around an iron nail and connect it to a battery. They count how many paper clips each configuration picks up, systematically varying coil number while keeping current constant, then voltage while keeping coil number constant. Groups share results on a class data table and draw conclusions about each variable.

50 min·Small Groups

Engineering Design Challenge: Electromagnet for a Purpose

Each group receives a design brief: build the strongest electromagnet possible from given materials, or build one that can be switched on and off remotely, or build one that lifts exactly 10 paper clips (not more, not fewer). Groups plan, build, test, and present their design rationale and results to the class.

55 min·Small Groups

Gallery Walk: Electromagnet Applications

Post images and brief descriptions of six electromagnetic technologies (electric motor, MRI scanner, maglev train, electric guitar pickup, hard disk, junkyard crane). Pairs visit each station, identify which factors (coil count, current, core material) are engineered for each application, and explain why. The class shares the most interesting engineering decision from each station.

30 min·Pairs

Real-World Connections

• MRI technicians use powerful electromagnets to generate detailed images of the inside of the human body, aiding in medical diagnosis.
• Engineers designing electric motors for vehicles, appliances, and industrial machinery rely on the principles of electromagnetism to convert electrical energy into mechanical motion.
• Sound engineers utilize electromagnets in speakers to vibrate a diaphragm, producing the sound waves we hear.

Assessment Ideas

Quick Check

Present students with three electromagnets, each with a different number of wire coils. Ask them to predict which will be strongest and then test them by counting how many paper clips each can pick up. Discuss why the results match their predictions.

Discussion Prompt

Pose the question: 'Imagine you need to build an electromagnet to sort iron ore from other rocks. What factors would you adjust to make your electromagnet as strong as possible?' Guide students to discuss coil number, current, and core material.

Exit Ticket

On an index card, ask students to draw a simple diagram of an electromagnet and label the parts that affect its strength. Then, have them write one sentence explaining how increasing the current would change the electromagnet's power.

Frequently Asked Questions

How does an electric current create a magnetic field?

Moving electric charges (current) generate a magnetic field around the wire they flow through. When wire is coiled, each loop's field adds together, creating a stronger, more concentrated field. An iron core inside the coil amplifies this further because iron's atomic magnetic domains align with the field, multiplying the strength significantly.

What factors affect how strong an electromagnet is?

Three main factors: the number of wire coils (more coils = stronger field), the amount of current (more current = stronger field), and the core material (ferromagnetic cores like iron amplify the field far more than air or non-magnetic materials). These are all independently testable, which makes electromagnets an ideal controlled experiment topic.

Where are electromagnets used in everyday technology?

Electromagnets are in electric motors (fans, appliances, EVs), MRI scanners in hospitals, speakers and headphones, electric guitar pickups, hard disk drives, and electromagnetic cranes in scrap yards. Their controllability -- the ability to switch them on and off and vary their strength -- is what makes them more useful than permanent magnets for most engineering applications.

How does active learning support understanding of electromagnets?

The relationship between current and magnetism is not obvious from everyday experience. Building an actual electromagnet and testing variables directly gives students experimental evidence for each factor. When groups each test a different variable and share data, they experience distributed scientific inquiry -- each group contributes one piece and the class assembles the full picture together.