Arrive on timeUse laptops only for legitimate class activities (note-taking, assigned tasks). Put mobile phones away

Do not leave class early without okaying it with the tutor in advance.

Ask questions/ clarification if you are confused.-Try not to distract or annoy your classmates. -Listen actively and attentively

Exploring Magnetic Fields

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Your imagination is all that is needed to create a unique masterpieceYou have 5 mins to build a structure that can hold an egg using the GeoMag providedSTARTER

Learning ObjectivesDescribe magnets and the concept of magnetism

Predict the motion of magnets based on the knowledge of magnetic poles (polarity) and flux lines.

Illustrate understanding of magnetic fields

Health and SafetyCaution: Safely working with iron filings

To avoid accidentally getting iron filings in the eyes during this session, safety glasses are provided!! WARNING !! Do not bring bar magnets near computers, computer monitors, audio tapes, or other such magnetic devices. Strong magnets can destroy materials with magnetic properties.0.0005 Tesla

What is a Magnet?What Materials are Magnetic?

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MagnetismSince ancient times, certain materials, called magnets, have been known to have the property of attracting tiny pieces of metal. This attractive property is called magnetism.

As fridge magnetsDid you know - A fridge magnet has a magnetic field that is about 20 times stronger than the earth!?Bar magnets are used within a car's oil filter to help remove any ferromagnetic materials which could damage the engine. By doing this it makes the engine last longerMagnetic catches on doors to hold them shut.They are used inside pickups in guitars to create different tones. The bar magnet is placed inside the pickup with a length of wire coiled around it to create a magnetic field. Whenever a guitar string vibrates in that magnetic field, the coil detects the changes and then creates a voltage, thus producing a perfect sound.

What Materials are Magnetic?

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What Do Magnets Do?ACTIVITY 110 minsLook at the pairs of magnets provided for you. Which pair will attract each other and why?

What Do Magnets Do?Attract or repel other magnets (exert a force)

Attract other magnetic metals

Have at least 2 distinct ends (poles) each

Like poles repel, opposite poles attract

Notes:Do not need to touch to exert force (can exert force through empty space)Can turn other magnetic metal objects into temporary magnets

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Magnetic Attraction-RepulsionMagnetic Forces: Like Poles RepelUnlike Poles Attract

Always Remember!!

Magnetic Poles(Polarity)The strength of a magnet is concentrated at the ends, called north and south poles of the magnet.A suspended magnet: N-seeking end and S-seeking end are N and S poles.

Activity 2An Investigation 15 minsPlace a bar magnetundera piece of paper. Sprinkle some iron filings (thousands of tiny pieces of iron) on top of the paper. What do you notice?

What is a magnetic field? Science experiments using a bar magnet

A magnetic field exerts an invisible force in the space surrounding a magnet.

This invisible force can pull other magnetized metals (such as iron) towards it and can attract or repel other magnets. If we cant see a magnetic field, how do we know what it looks like?

Just as we can see the outline of the invisible mans head through his bandages, so we can see a magnetic field if we conduct the following science experiment using iron filings:

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A magnet is anything that produces a magnetic field. Can you see the magnetic field surrounding the bar magnet below? No? Why not?

The iron filings have interacted with the magnets magnetic field to produce a pattern that should look very much like the image below.

The pattern made by the iron filings has been drawn in the diagram below. What do you notice?

The arrows show the direction of attraction of each line of force.

The direction of attraction isalwaysfrom north to south. These lines of force originate at the north pole, travel through space and enter the magnet through the south pole.

The lines of force never cross each other (intersect).

The magnetic field is strongest where the lines of force are closest together.

Representation of Magnetic FieldLike electric field, can be represented by field linesField direction indicated by direction of linesField strength indicated by density of linesBut, unlike electric fieldMagnetic field lines perpendicular to forceNo isolated magnetic poles, so no points in space where field lines begin or end

Magnetic Field LinesWe can describe magnetic field lines by imagining a tiny compass placed at nearby points.The direction of the magnetic field B at any point is the same as the direction indicated by this compass. Field B is strong where lines are dense and weak where lines are sparse.

Field Lines Between MagnetsUnlike polesLike polesLeave N and enter SAttractionRepulsion

Importance of Magnetic FieldsPractical UsesElectric motors, Loud speakers, Navigation (Earths magnetic field)

In Experimental PhysicsMass spectrometers, Particle accelerators, Plasma confinement

In the UniverseStars (e.g. the Sun), Interstellar space, Intergalactic structure, Jets

Have we met our objectivesDescribe magnets and the concept of magnetism

Predict the motion of magnets based on the knowledge of magnetic poles (polarity) and flux lines.

Illustrate understanding of magnetic fields

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