First Introduction to Magnetism

 

Subject Area

  Magnetism
Age or Grade

 Grade 9-10 
Estimated Length

 1-2 periods 
Prerequisite knowledge/skills

 mechanical forces 
Description of New Content

 Magnets, magnetic fields, magnetization 
Goals

 This lesson is a first introduction to the field of magnetism. The students should explore the basic properties of magnets hands on. By the end of the lesson they should now about: magnetic north and south poles (attractive and repulsive forces), magnetic and non magnetic materials, magnetization of materials, use of compasses(magnets) as magnetic field detectors, the magnetic field and visualization of magnetic field lines 
Materials Needed


 Most of these things can be cheaply bought at Home Depot or online science stores (e.g. sciencefirst, physlink)

1. collection of magnets of different size, shape and strength
2. ring magnets and pens or post to demonstrate repulsion of magnets
3. different magnetic and non magnetic materials (I used zinc and brass nails)
4. compasses
5. something to visualize magnetic field lines (e.g. ironfiles on paper or cube iron filing solution)
6. natural magnetic rocks

Procedure

 

 

 

 We handed a worksheet to the students before the class:


Opener  

Ask the students what they know about magnets and where magnets are being used or what they think they are good for. We gave them some time to think about their answers. After a short discussion let them experiment with magnets

Development

Students experiment with magnets. Explore that there can be attraction and repulsion between magnets and that the strength of the magnetic force depends on the distance between the magnets
Students are handed magnetic (zinc nails) and non magnetic materials (brass nails). The materials are not magnetic by themselves (2 nails don't attract each other) but are being magnetized by the magnet, which is shown by the fact that one can build chains of nails hanging below a magnet. Also close to the poles of a bar magnet small nails tend to stand up along the field lines (the field will be introduced later)
Discuss what compasses are and what they are used for, give students compasses and let them explore the behaviour close to the magnets. The compasses can be used as detectors of magnetic fields, point in the north/south direction and align along field lines
Use compasses as detectors to detect the magnetic field of natural, magnetic rocks
Discuss the concept of the magnetic field, visualize with the 3D iron file cube

Closure

 We gave students as homework to think about and research some of the widespread applications of magnets 
Evaluation

  It is good for the students to slowly and interactively explore the phenomenon of magnetism. On can imagine bringing even more little gadgets which use magnets. One can also in class discuss several applications of magnets (e.g. in computer hard drives). My favorite is the magnet which is build into cell phones to detect if they are opened or closed (it should be possible to visualize the postion of the magnet with magnet paper)
Extensions

  
References  Active Phyiscs, Conceptial Physics, any basic text about magnetism,