Teaching Minds-On Experiments on Electromagnetism in Secondary Schools

Permanent magnets
Repelling force: measurement based on gravity: how many to reduce the distance to halve?

Two magnets are inserted into a tube with the same poles facing each other. They repel. When the tube is placed in a vertical position, the magnet on top remains suspended as an effect of the repulsion between the similar poles of the two magnets. If we add small weights (of a non magnetic material) on top of the upper magnet, the distance between the two magnets is reduced observing an inverse power law.
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