Magnetic Force Reference Lessons

Magnetic Force

Learning Objectives

• Define magnetism, magnetic forces, and magnetic poles.

• Explain permanent magnets, temporary magnets, and electromagnets.

• Describe magnetic fields and model their field lines.

• Discover Earth's magnetic field and its vital roles.

• Magnets create magnetic fields, attracting iron, nickel, or cobalt.

• Magnetism is an invisible force of attraction or repulsion.

• Magnets turn magnetic items magnetic! They ignore wood or plastic.

• Some magnets are permanent, some temporary. Earth is a giant magnet!

What are Magnets and Magnetism?

Multiple Choice

Which of the following materials would a magnet most likely attract?

• A wooden block

• A copper penny

• A steel paperclip

• A plastic toy

• Magnets have North (N) & South (S) poles where force is strongest.

• Magnetic force is a push or pull acting at a distance.

• Like poles repel (push away); opposite poles attract (pull together).

• Break a magnet? You get two new magnets, each with N/S poles!

Magnetic Poles and Force

Multiple Choice

What happens when the south pole of one magnet is brought near the south pole of another magnet?

• They attract each other strongly

• They repel each other

• Nothing happens, poles only affect magnetic materials

• One magnet loses its magnetism

• Magnetic domains: tiny zones of aligned atomic magnets.

• ​Non-magnetic items: domains are random, effects cancel out.

• Iron's jumbled domains can align near a strong magnet.

• Permanent magnets: many domains permanently aligned one way.

Magnetic Domains: Tiny Magnet Powerhouses!

Multiple Choice

What are magnetic domains?

• The poles of a magnet

• Tiny regions within magnetic materials where groups of atoms have their magnetic fields aligned

• Imaginary lines showing magnetic field direction

• Particles that carry magnetic force

​​Permanent Magnets: Always Magnetic!

• ​Easy to magnetize using another magnet.

• ​​Magnetic domains align only for a short time.

• ​Lose magnetism when magnet is taken away.

​​Temporary Magnets: Magnetic for a Moment!

Types of Magnets: Permanent and Temporary

• ​Made from materials like iron or nickel.

• ​​Their magnetic domains stay aligned for long.

• ​Can lose magnetism if heated or dropped.

Multiple Choice

Which of these materials are commonly used to make permanent magnets (ferromagnets)?

• Copper, aluminum, and gold

• Iron, nickel, and cobalt

• Plastic, wood, and glass

• Lead, tin, and zinc

• Electromagnets are temporary magnets made with electric current in a coiled wire.

• Their magnetic field only exists when current flows; it stops with the current.

• Stronger with: an iron core, more current, or more wire coils.

• Useful as they are controllable; used in motors, speakers, and cranes.

Special Temporary Magnets: Electromagnets

Multiple Choice

How can the strength of an electromagnet be increased?

• By using a wooden core

• By decreasing the electric current

• By increasing the number of wire coils around the core

• By removing the core material

• A magnetic field is an invisible force area around magnets.

• It lets magnets attract or repel without touching (action at a distance).

• Fields are strongest at poles and weaken with distance.

• We can see field patterns with iron filings or a compass.

What are Magnetic Fields?

Multiple Choice

Where is the magnetic field around a bar magnet typically the strongest?

• In the exact middle of the magnet, furthest from the poles

• Equally strong everywhere around the magnet

• At its North and South poles

• Only on the surface of the magnet

Visualizing Fields: Single Magnet Field Lines

The arrows show how magnetic field lines travel from the north (N) pole to the south (S) pole around a bar magnet. Where the lines are closer together, the magnetic field is stronger.

Multiple Choice

Which statement accurately describes magnetic field lines of a single bar magnet?

• They start at the south pole and end at the north pole, going through the magnet

• They often cross each other where the field is particularly strong to show intensity

• They form complete loops, emerging from the north pole and entering the south pole externally

• They are always evenly spaced, indicating uniform field strength everywhere

• Close magnets? Their magnetic fields mix and merge.

• Like poles (N-N, S-S)? Fields push apart, repelling!

• Opposite poles (N-S)? Fields connect, becoming stronger there!

• Cool fact: Magnetic field lines never, ever cross!

Magnetic Field Mashup: How They Combine!

Multiple Choice

What happens to the magnetic field lines when the south pole of one magnet is placed near the north pole of another magnet?

• The field lines push away from each other, showing repulsion

• The field lines disappear completely between the two magnets

• The field lines from the two magnets connect, showing attraction between the poles

• The field lines cross over each other multiple times in the space between

• Magnets store potential energy based on their place and forces.

• Pull N and S poles apart? You're boosting their potential energy!

• Push N and N poles together? That also boosts potential energy!

• Let magnets move? Potential energy becomes kinetic energy (motion)!

Magnets and Potential Energy

Multiple Choice

When does the potential energy of a system of two magnets increase?

• When opposite poles are allowed to move closer together naturally

• When like poles (e.g., two North poles) are pushed closer together against their repulsive force

• When the magnets are very far apart and not interacting

• When one of the magnets is broken in half

• Earth acts like a giant magnet from molten iron.

• It has magnetic North/South poles near geographic poles.

• Its magnetic field, the magnetosphere, is strongest at poles.

• Compasses point to magnetic North (a South-type pole!).

Earth: The Giant Magnet

Multiple Choice

How does Earth's magnetic field assist with navigation?

• It creates ocean currents that guide ships

• It allows a compass needle to align with the field lines, pointing towards the magnetic north pole

• It makes certain stars brighter to follow at night

• It generates radio waves that GPS devices use directly

• The Sun zaps out solar wind – a stream of super tiny charged particles!

• Earth's magnetic field (magnetosphere!) acts like a giant shield, protecting us.

• Some particles get guided to the poles, crashing into gases (like oxygen/nitrogen) way up high.

• Gases glow as auroras: Northern Lights (Aurora Borealis) and Southern Lights (Aurora Australis).

Earth's Magnetic Shield and Auroras

Multiple Choice

What primarily causes the auroras (Northern and Southern Lights)?

• Reflection of city lights off the atmosphere

• Charged particles from the solar wind interacting with gases in Earth's upper atmosphere near the poles

• Sunlight passing through ice crystals high in the atmosphere

• Volcanic eruptions releasing luminous gases

​Correction

• Not all metals! Only some, like iron, are strongly magnetic.

• Nope! Magnetic force acts from a distance through invisible fields.

• Surprise! Breaking a magnet makes two new, smaller magnets, each with N and S poles.

• Earth's geographic North Pole is near its magnetic south-seeking pole. This guides compasses north.
  

​Misconception

Common Misconceptions

• All metals are magnetic.

• Magnetic force needs direct contact.

• Breaking a magnet gives one N and one S pole.

• Earth's geographic North Pole is its magnetic North pole.
  

Summary

• Magnets exert forces, strongest at poles; like poles repel, opposites attract.

• Materials become magnetic when tiny domains inside them align.

• Electromagnets are temporary magnets made using electric current in a wire.

• Earth acts like a giant magnet, guiding compasses and protecting us.

Open Ended

What are the two types of poles every magnet has, and how do they interact with opposite poles?

Open Ended

Briefly explain what makes an electromagnet different from a permanent magnet.

Poll

Earth's magnetic field creates the auroras by interacting with:

• Cosmic rays

• Solar wind particles

• Moonlight

• Radio waves

Poll

On a scale of 1 (not at all) to 4 (very well), how well do you feel you understand why some materials are magnetic (hint: domains)?

• 1

• 2

• 3

• 4

Open Ended

What is one concept from today's review on magnetism that you would like to explore further or found most interesting?