028 – Load capacity of a bar magnet

Field strength of a bar magnet 

Introduction to:  

Field strength, magnetic field, field lines 

Material:  

• Bar magnet  
• Screws (ferromagnetic, ferrous) / iron or steel nails with heads (length 2-3 cm) / paper clips.  

Setup and execution:  

• Put one screw after the other on the magnet hanging freely until the last one does not hold anymore.   
• Test the magnet’s load-bearing capacity at various points of the magnet, especially at the poles and in the middle.  
• Slide the chain of screws from the poles to the center.  

Observation:  

•     The poles can hold up the most screws.  
•     The screws can “conduct” the magnetic effect.  
•     As you move the screws towards the center, they drop off one by one.  

Tip:  

Do not place screws too close together or they will attract each other.  

Explanation:  

• The magnetic field, as well as the gradient of the magnetic field, are strongest at the poles.
• The screws are magnetized as a result.
• In the center, the field lines run perpendicular to the screws and thus attract them very weakly.