Magnetic Force

Magnetic Force

Learning Objectives

• Define magnetism and magnetic force, identifying magnetic poles and their interactions.

• Describe how potential energy changes in a system of magnets based on their arrangement.

• Explain magnetic fields and model their lines for single or combined magnets.

• Describe Earth's magnetic field and its role in navigation and solar wind protection.

• A magnet attracts iron and things with iron in them.

• Magnetism is the force of attraction or repulsion from magnets.

• Magnets can attract or repel other magnets; Earth is a giant magnet.

• Some magnets are permanent; others, like paperclips near magnets, are temporary.

Meet Magnets and Magnetism!

Multiple Choice

What is magnetism?

• The force only between two magnets

• The attraction or repulsion involving magnets

• The property of iron only

• The energy stored in a magnet

​​Like Poles: Push Apart!

• ​North (N) and South (S) poles attract.

• ​​This means they pull towards each other.

• ​Magnets also pull objects like paper clips!

​​Opposite Poles: Pull Together!

Magnetic Force and Poles

• ​North poles (N) near North poles (N) repel.

• ​​South poles (S) near South poles (S) repel.

• ​This means they push each other away.

Multiple Choice

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

• They attract each other

• They repel each other

• Nothing happens

• They become one magnet

​​Increasing Potential Energy

• Opposite poles moving together release energy.

• Like poles moving apart also release energy.

• Magnetic forces do the work, lowering energy.

​​Decreasing Potential Energy

Magnets and Potential Energy

• Pulling opposite poles apart stores more energy.

• Pushing like poles together also stores energy.

• This means you do work against magnetic forces.

Multiple Choice

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

• When opposite poles are allowed to move closer

• When like poles are pushed closer together

• When the magnets are removed from the system

• When the magnets stop interacting

• Magnetic field: area around a magnet with magnetic force.

• Contains magnetic energy; lets magnets push/pull from afar.

• Strongest at poles; extends from one pole to another.

• Invisible, but iron filings can reveal its pattern.

What are Magnetic Fields?

Multiple Choice

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

• In the middle of the magnet

• Equally strong everywhere

• At the North and South poles

• Only outside the magnet

• Magnetic field lines are like invisible maps for magnets!

• They show a magnet's strength and which way it pulls.

• Lines go from North to South pole, forming complete loops.

• Closer lines mean stronger power; lines never ever cross!

Magnetic Field Lines: The Invisible Map!

Multiple Choice

Which statement accurately describes magnetic field lines?

• They start at the south pole and end at the north pole

• They often cross each other where the field is strong

• They form complete loops from the north pole to the south pole

• They are closest together where the field is weakest

​​Opposite Poles: Attraction Zone!

• Like poles push away from each other.

• Magnetic field lines bend sharply apart.

• No direct connection between these poles.

​​Like Poles: Repulsion Zone!

Visualizing Fields: Combined Magnetic Fields

• Opposite poles pull towards each other.

• Magnetic field lines connect them directly.

• This creates a very strong field.

Multiple Choice

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

• The field lines push away from each other

• The field lines disappear between the magnets

• The field lines combine to form a strong field between the magnets

• The field lines cross over each other

• Earth's core materials make it a giant magnet.

• Its 3D magnetic field is donut-shaped, like a bar magnet's.

• Field is strongest near magnetic poles, close to geographic poles.

• Compasses use this field for navigation, pointing North.

Earth: The Giant Magnet

Multiple Choice

How is Earth's magnetic field useful for navigation?

• It makes ships float higher

• It allows compass needles to align with the field lines, pointing towards the magnetic poles

• It creates visible lines in the sky to follow

• It pushes airplanes in the right direction

• The sun sends out solar wind: speedy, charged particles.

• Earth’s magnetic field acts like a giant, invisible shield.

• It pushes most harmful solar particles towards the poles.

• Collisions create beautiful auroras, the Northern and Southern Lights!

Earth's Awesome Shield & Sky Show!

Multiple Choice

What causes auroras (Northern/Southern Lights)?

• Sunlight reflecting off ice crystals

• Charged particles from solar wind colliding with atmospheric gases near the poles

• Moonlight interacting with the magnetic field

• Artificial lights from cities reflecting off clouds

​Correction

• Magnets attract some materials; they repel/attract other magnets.

• Magnetic force acts at a distance via invisible fields.

• Field lines show force direction and never cross.

• Geographic North Pole is near Earth's magnetic south pole.
  

​Misconception

Common Misconceptions

• Magnets only attract things.

• Magnetic force needs objects to touch.

• Magnetic field lines can cross over.

• Geographic North Pole is magnetic north.
  

Summary

• Magnets attract iron & metals. They attract/repel other magnets (magnetism).

• Magnetic force: push/pull, strongest at poles. Like poles repel, opposites attract.

• Magnetic field: force area around magnet, shown by field lines (N→S).

• Earth is a magnet; its field aids navigation and creates auroras.

Open Ended

What are the two types of poles every magnet has?

Open Ended

Describe what happens to the potential energy when you push the north poles of two magnets together.

Poll

Earth's magnetic field protects us from:

• Meteorites

• Solar Wind

• Loud Noises

• Cold Weather

Poll

How confident are you in explaining how magnetic poles interact? (Rate 1-4, 1=Not confident, 4=Very confident)

• 1

• 2

• 3

• 4

Open Ended

What part of today's lesson was most confusing or needs more explanation?