020 – Magnetization

Introduction to: 

Magnetization by means of permanent magnet, ferromagnetism, magnetic needle, compass, Earth’s magnetic field, north and south pole 

Material:

• Permanent magnet (e.g. bar magnet, as strong as possible) 
• Razor blade with a marking (e.g. red dot) 
• Bowl with water 

 Material (alternative):

• needle (e.g. pin) (1)
  
• cork / styrofoam / wooden discs (2) 
• Permanent magnet (e.g. bar magnet, as strong as possible) 
• Bowl with water 

Construction and implementation:

• Run one pole of the permanent magnet over the razor blade several times in the same direction, preferably over the top and the bottom. 
• Carefully place the razor blade on the surface of the water. 
• It always returns to the north-south direction, even if you turn it. 

Explanation:

• By running the permanent magnet over the razor blade, the magnetic domains in the iron align.
• This turns the razor blade itself into a magnet. 

Didactic potential:

• A nice brain teaser is to figure out the orientation of the razor blade. Do not forget that there is a magnetic south pole at the geographic north pole of the Earth. 
• The experiment consolidates the model of the elementary magnets in iron. 

Tips:   

• The magnetisation can be reversed by strong vibration/shock 
• Caution: Move the permanent magnet far away from the bowl to prevent interference with the magnetic field of the Earth 

Tips for alternative material:  

• Before attaching the needle to the cork disc, test whether it is really magnetized (for example, hold it against a needle that has not yet been magnetized). 
• Modelling clay works well for attaching the needle, glue is also possible