Real-world examples of comparing permanent magnets to electromagnets

Lab-first examples of comparing permanent magnets to electromagnets

If you want students to really understand the difference, start with side‑by‑side tests. The best examples are simple enough to build in a classroom but rich enough to raise good questions.

Bench-top example of permanent vs. electromagnet lifting power

Set up a permanent bar magnet and a homemade nail electromagnet on the same table. Use identical paper clips or steel washers as test objects. This is one of the clearest examples of comparing permanent magnets to electromagnets in a beginner lab.

You can:

• Keep the distance from magnet to paper clips the same, using a ruler or a stack of index cards.
• Count how many clips each magnet can lift.
• For the electromagnet, vary the number of battery cells or the number of wire turns.

Patterns you’ll usually see:

• A strong neodymium permanent magnet often outperforms a weak electromagnet powered by a single AA battery.
• As you increase coil turns or voltage, the electromagnet can surpass the permanent magnet.

This simple setup gives one of the best examples of how permanent magnets have a fixed strength, while electromagnets can be tuned.

Examples of comparing permanent magnets to electromagnets in motors

Electric motors are full of opportunities to compare. In basic DC hobby motors, the stator is often a permanent magnet, while the rotor is an electromagnet. That means every spin of the motor is literally an ongoing comparison between the two types.

Use a cheap DC motor with a transparent housing or a disassembled brushed motor. Ask students to identify:

• The permanent magnet parts (usually curved gray or silver pieces around the inside).
• The coil windings on the rotor that become electromagnets when current flows.

Then discuss real examples:

• Small DC motors in toys and fans often use permanent magnets because they’re compact and don’t need external field windings.
• Large industrial motors typically use electromagnets for the stator field so engineers can control torque and speed more precisely.

This is a practical example of how design choices balance cost, control, and efficiency rather than simply picking “the stronger magnet.” For background on motor design and magnetic fields, the U.S. Department of Energy’s energy education materials are useful: https://www.energy.gov/energysaver/energy-department-resources

Loudspeakers: a clean audio example of comparing permanent magnets to electromagnets

Speakers are a favorite classroom demo because they’re everywhere and easy to take apart.

Inside a typical loudspeaker:

• A permanent magnet provides a steady magnetic field.
• A voice coil acts as an electromagnet when audio current passes through it.

When the audio signal changes direction and strength, the electromagnet’s interaction with the permanent magnet pushes and pulls the speaker cone, creating sound. This gives one of the clearest examples of comparing permanent magnets to electromagnets in a consumer device:

• The permanent magnet sets the background field.
• The electromagnet provides the variable, controllable part.

You can extend this with a lab:

• Connect a loose voice coil to a function generator or audio source.
• Hold it near a strong permanent magnet.
• Let students feel the vibration or measure the motion with a simple displacement sensor.

For more on how speakers use electromagnetism, see educational resources from MIT OpenCourseWare: https://ocw.mit.edu

Magnetic locks and door buzzers: switching matters

Magnetic door locks and buzzers offer real examples of where being able to switch a magnet on and off is more important than raw strength.

Compare:

• A permanent magnet latch on a cabinet: always on, no power needed, but you can’t switch it off remotely.
• An electromagnetic door strike: only locks when powered, or only releases when powered, depending on design.

In class, you can:

• Use a small permanent magnet latch to hold a metal plate.
• Build a basic electromagnet latch with a coil and a movable iron armature.
• Measure how much weight each can hold at a given gap.

This gives one of the best examples of how control can outweigh constant availability. A permanent magnet wins for battery-free reliability. An electromagnet wins when remote control and integration with electronics (keypads, card readers, smart home systems) matter more.

Data storage: from permanent magnet domains to electromagnets in write heads

Modern storage technology also offers strong examples of comparing permanent magnets to electromagnets, especially in traditional hard disk drives.

Inside a magnetic hard drive:

• The disk surface acts like a collection of tiny permanent magnets (magnetic domains) that stay aligned to store bits.
• The write head uses an electromagnet to flip those domains when data is written.

So, the system literally combines:

• Permanent magnet behavior for long-term storage.
• Electromagnet behavior for fast, precise writing.

You can connect this to current trends (2024–2025):

• Higher‑density drives rely on more precise magnetic field control, often using advanced head designs and materials.
• Solid-state drives (SSDs) don’t use magnets at all, which is a good contrast to discuss when students assume “all memory is magnetic.”

For deeper background on magnetism in storage media, the National Institute of Standards and Technology (NIST) has accessible explanations of magnetic materials and domains: https://www.nist.gov

Transportation: maglev trains and magnetic braking

Maglev systems and magnetic brakes give dramatic, large‑scale examples of comparing permanent magnets to electromagnets in transportation.

In some maglev train designs:

• Permanent magnets can provide passive levitation in certain configurations.
• Electromagnets (or superconducting electromagnets) are used for active levitation and propulsion, allowing precise control over lift and thrust.

In magnetic braking systems (for example, in some roller coasters and rail systems):

• Permanent magnets create a steady magnetic field.
• Moving conductive fins or disks generate eddy currents that act like temporary electromagnets, producing drag without physical contact.

Classroom tie‑in:

• Use a simple aluminum track and a magnet to show eddy current braking with a falling magnet or a sliding metal block.
• Contrast this with a coil carrying current near a magnet, where you can switch the braking effect on and off.

This gives a real example of how engineers choose between permanent magnets (low maintenance, always on) and electromagnets (controllable, but power‑hungry) in large infrastructure projects.

Medical imaging: MRI scanners vs. small permanent magnet devices

Medical technology offers powerful examples of comparing permanent magnets to electromagnets at very different scales.

MRI scanners:

• High‑field clinical MRI machines (1.5–3 tesla, and research systems even higher) use superconducting electromagnets cooled with liquid helium.
• The field can be ramped up and, in principle, ramped down, though in practice it’s usually kept on.

Small permanent magnet devices:

• Handheld magnetic therapy gadgets and some portable imaging or sensing tools use permanent magnets for simplicity.

This contrast highlights:

• Electromagnets in MRI allow very strong, uniform fields over a large volume, something permanent magnets struggle to provide at the same scale.
• Permanent magnets shine in small, portable devices where field strength demands are lower and power supplies are limited.

For medically accurate information on MRI safety and magnetic fields, the National Institutes of Health (NIH) and related resources are reliable starting points: https://www.nibib.nih.gov

Classroom comparison: cost, energy, and safety

Beyond “which is stronger,” some of the best examples of comparing permanent magnets to electromagnets focus on trade‑offs:

• Energy use: Permanent magnets require no ongoing power. Electromagnets draw current and can heat up. In a lab, you can measure battery life when running a coil versus doing the same task with a permanent magnet.
• Adjustability: Electromagnets can be turned on and off and adjusted with current. Permanent magnets require mechanical changes (distance, shielding, or swapping magnets) to change the effect.
• Size and weight: For a given field strength, permanent magnets can be compact, but high‑field applications (like MRI) favor electromagnets that can be engineered to large sizes.
• Safety: Strong permanent magnets can pinch fingers or damage electronics and are always active. Electromagnets can be shut down in an emergency, but overheating and electrical hazards must be managed.

A simple data table from a class experiment—showing field strength versus current for an electromagnet and a fixed value for a permanent magnet—can make this comparison very concrete.

Designing your own examples of comparing permanent magnets to electromagnets

Once students have seen a few real examples, encourage them to design their own comparisons. The best examples usually follow a few guidelines:

• Same task, different magnet: Have both a permanent magnet and an electromagnet do the same job—lifting, deflecting a compass, triggering a sensor—so the difference is clear.
• Measurable outcome: Count lifted objects, measure distance, or use a smartphone magnetometer app to record field strength.
• Variable to control: For the electromagnet, change current or coil turns. For the permanent magnet, change distance or add a steel “keeper” to alter the field path.

Examples include:

• A magnetic crane model where students can swap between a permanent magnet hook and an electromagnet hook and compare how easy it is to drop the load on command.
• A magnetic door alarm with a reed switch triggered by a permanent magnet, then redesigned with an electromagnet to show how you might remotely arm or disarm the system.

By the time students have built two or three of these, they can usually explain the physics and the engineering trade‑offs without memorizing definitions.

FAQ: Short answers built around real examples

Q: What are some simple classroom examples of comparing permanent magnets to electromagnets?
A: Lifting paper clips with a bar magnet versus a nail electromagnet, dissecting a small DC motor to see permanent and electromagnet parts, and examining a loudspeaker’s permanent magnet and voice coil are all easy, low‑cost examples.

Q: Can you give an example of when a permanent magnet is better than an electromagnet?
A: Refrigerator door seals, cabinet latches, and basic compasses are good examples. They don’t need power, must work continuously, and don’t require adjustable strength.

Q: Can you give an example of when an electromagnet is better than a permanent magnet?
A: Magnetic cranes in scrap yards, MRI scanners, and electromagnetic door locks are classic cases. The ability to switch the field on and off or control its strength is more important than never needing electricity.

Q: Are there real examples where devices use both permanent magnets and electromagnets together?
A: Yes. Loudspeakers, many DC motors, and hard disk drives all combine permanent magnets with electromagnets. In these systems, the permanent magnet provides a steady field, while the electromagnet handles the controllable part of the interaction.

Q: How can I avoid keyword stuffing when teaching with examples of magnets?
A: Focus on clear, specific real examples first—motors, speakers, locks—then describe how each uses permanent magnets, electromagnets, or both. When students understand the devices, the terminology follows naturally.